All Diagnostic Tests
ALL DIAGNOSTIC PROCEDURES
This section contains information about all the commonly used diagnostic tests in medicine. As a transcriptionist, one must be familiar with the names and the significance of each test though a detailed information is usually not required. Hence, it would be appropriate if one can remember each test and its significance. Remember this is only for educational and informational purposes.
Computed tomography (CT), originally known as computed axial tomography (CAT) is a medical imaging method employing tomography where digital geometry processing is used to generate a three-dimensional image of the internals of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation. The word "tomography" is derived from the Greek tomos (slice) and graphia (describing). CT produces a series of axial images, which can be manipulated, through a process known as windowing, in order to recreate the image in a different plane.
X-ray slice data is generated using an X-ray source that rotates around the object; X-ray sensors are positioned on the opposite side of the circle from the X-ray source. Many data scans are progressively taken as the object is gradually passed through the gantry. They are combined together by the mathematical procedure known as tomographic reconstruction.
Since its introduction in the 1970s, CT has become an important tool in medical imaging to supplement X-rays and medical ultrasonography. Although it is still quite expensive, it is the gold standard in the diagnosis of a large number of different disease entities.
Diagnosis of cerebrovascular accidents and intracranial hemorrhage is the most frequent reason for a "head CT" or "CT brain". Scanning is done without intravenous contrast agents (contrast may resemble a bleed). CT generally does not exclude infarct in the acute stage, but is useful to exclude a bleed (so anticoagulant medication can be commenced safely).
For detection of tumors, CT scanning with IV contrast is occasionally used but is less sensitive than magnetic resonance imaging (MRI). CT can also be used to detect increases in intracranial pressure, e.g. before lumbar puncture or to evaluate the functioning of a ventriculoperitoneal shunt. CT is also useful in the setting of trauma for evaluating facial and skull fractures.
In the head/neck/mouth area, CT scanning is used for surgical planning for craniofacial and dentofacial deformities, evaluation of cysts and some tumors of the jaws/sinuses/nasal cavity/orbits, and for planning of dental implant reconstruction.
Chest CT is excellent for detecting both acute and chronic changes in the lung parenchyma. For detection of airspace disease (such as pneumonia) or cancer, ordinary non-contrast scans are adequate. For evaluation of chronic interstitial processes (emphysema, fibrosis, and so forth), thin sections with high spatial frequency reconstructions are used. For evaluation of the mediastinum and hilar regions for lymphadenopathy, IV contrast is administered.
CT angiography of the chest (CTPA) is also becoming the primary method for detecting pulmonary embolism (PE) and aortic dissection, and requires accurately timed rapid injections of contrast and high-speed helical scanners. CT is the standard method of evaluating abnormalities seen on chest X-ray and of following findings of uncertain acute significance.
With the advent of subsecond rotation combined with multi-slice CT (up to 64 slices), high resolution and high speed can be obtained at the same time, allowing excellent imaging of the coronary arteries. Images with high temporal resolution are formed by updating a proportion of the data set used for image reconstruction as it is scanned. In this way individual frames in a cardiac CT investigation are significantly shorter than the shortest tube rotation time. It is uncertain whether this modality will replace the invasive coronary catheterization.
Dual Source CT scanners, introduced in 2005, allow higher temporal resolution when acquiring images of the heart, allowing a greater number of patients to be scanned.
Abdominal and pelvic CT
Many abdominal disease processes require CT for proper diagnosis. The most common uses include diagnosis of renal/urinary stones, appendicitis, pancreatitis, diverticulitis, abdominal aortic aneurysm, and bowel obstruction. CT is also the first line for detecting solid organ injury after trauma. Oral and/or rectal contrast is usually administered (more often iodinated contrast than barium due to the tendency of barium to cause imaging artifacts that limit evaluation of abdominal structures).
CT has limited application in the evaluation of the pelvis. For the female pelvis in particular, ultrasound is the imaging modality of choice. Nevertheless, it may be part of abdominal scanning (e.g. for tumors), and has uses in assessing fractures.
CT is also used in osteoporosis studies and research along side DXA scanning. Both CT and DXA can be used to asses bone mineral density (BMD) which is used to indicate bone strength, however CT results do not correlate exactly with DXA (the gold standard of BMD measurement), is far more expensive, and subjects patients to much higher levels of ionizing radiation, so it is used infrequently.
CT is often used to image complex fractures, especially ones around joints, because of the ability to reconstruct the area of interest in multiple planes.
Positron Emission Tomography
Positron emission tomography (PET) is a nuclear medicine medical imaging technique, which produces a three-dimensional image or map of functional processes in the body.
In PET, a short-lived radioactive tracer isotope, which decays by emitting a positron, chemically incorporated into a metabolically active molecule, is injected into the living subject (usually into blood circulation). The short-lived isotope decays, emitting a positron. These are detected when they reach a scintillator material in the scanning device, creating a burst of light, which is detected by photomultiplier tubes.
PET is a valuable technique for some diseases and disorders, because it is possible to target the radio-chemicals used for particular bodily functions.
Oncology: PET scanning with the tracer (18F) fluorodeoxyglucose (FDG, FDG-PET) is widely used in clinical oncology. This tracer is a glucose analog and is taken up by cells, phosphorylated by hexokinase (whose mitochondrial form is greatly elevated in rapidly-growing malignant tumors), and retained by tissues with high metabolic activity, such as the brain, the liver, and most types of malignant tumors. As a result FDG-PET can be used for diagnosis, staging, and monitoring treatment of cancers, particularly in Hodgkin's disease, non-Hodgkin's lymphoma, and lung cancer. However because individual scans are more expensive than conventional imaging with CT and MRI, expansion of FDG-PET in cost-constrained health services will depend on proper Health Technology Assessment. Oncology scans using FDG make up over 90% of all PET scans in current practice.
Neurology: PET neuroimaging is based on an assumption that areas of high radioactivity are associated with brain activity. What is actually measured indirectly is the flow of blood to different parts of the brain, which is generally believed to be correlated, and usually measured using the tracer oxygen (15O). Research continues into the use of radiolabeled F-DOPA and FDDNP as more specific probes.
Cardiology: In clinical cardiology FDG-PET can identify so-called "hibernating myocardium", but its cost-effectiveness in this role versus SPECT is unclear.
Neuropsychology / Cognitive neuroscience: To examine links between specific psychological processes or disorders and brain activity.
Pharmacology: In pre-clinical trials, it is possible to radio-label a new drug and inject it into animals. The uptake of the drug, the tissues in which it concentrates, and its eventual elimination, can be monitored far more quickly and cost effectively than the older technique of killing and dissecting the animals to discover the same information. PET scanners for rats and apes are marketed for this purpose.
PET scanning is invasive, in that radioactive material is injected into the subject. However the total dose of radiation is small, usually around 7 mSv.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) - also called magnetic resonance tomography (MRT) - is a method of creating images of the inside of opaque organs in living organisms as well as detecting the amount of bound water in geological structures. It is primarily used to demonstrate pathological or other physiological alterations of living tissues and is a commonly used form of medical imaging. MRI has also found many niche applications outside of the medical and biological fields such as rock permeability to hydrocarbons and certain non-destructive testing methods such as produce and timber quality characterization. Medical MRI most frequently relies on the relaxation properties of excited hydrogen nuclei in water.
In clinical practice, MRI is used to distinguish pathologic tissue (such as a brain tumor) from normal tissue. One of the advantages of an MRI scan is that, according to current medical knowledge, it is harmless to the patient. It utilizes strong magnetic fields and non-ionizing radiation in the radio frequency range. Compare this to CT scans and traditional X-rays which involve doses of ionizing radiation and may increase the chance of malignancy, especially in children receiving multiple examinations.
While CT provides good spatial resolution (the ability to distinguish two structures an arbitrarily small distance from each other as separate), MRI provides comparable resolution with far better contrast resolution (the ability to distinguish the differences between two arbitrarily similar but not identical tissues).
The presence of a ferromagnetic foreign body (such as shell fragments) in the subject, or a metallic implant (like surgical prostheses, or pacemakers) can present a (relative or absolute) contraindication towards MRI scanning: interaction of the magnetic and radiofrequency fields with such an object can lead to: trauma due to shifting of the object in the magnetic field, thermal injury from radiofrequency induction of heating of the object, or failure of an implanted device.
Some specialized MRI scans are:
1. Diffusion MRI measures the diffusion of water molecules in biological tissues.
2. Magnetic resonance angiography (MRA) is used to generate pictures of the arteries, in order to evaluate them for stenosis (abnormal narrowing) or aneurysms (vessel wall dilatations, at risk of rupture). The main use of MRA is to evaluate the arteries of the neck and brain, the thoracic and abdominal aorta, and the kidneys.
3. Magnetic resonance spectroscopy (MRS), also known as MRSI (MRS Imaging) and Volume Selective NMR Spectroscopy, is a technique which combines the spatially-addressable nature of MRI with the spectroscopically-rich information obtainable from nuclear magnetic resonance (NMR).
4. Functional MRI (fMRI) measures signal changes in the brain that are due to changing neural activity. The brain is scanned at low resolution but at a rapid rate (typically once every 2-3 seconds).
5. Interventional MRI - Because of the lack of harmful effects on the patient and the operator, MR is well suited for "interventional radiology", where the images produced by an MRI scanner are used to guide a minimally invasive procedure intraoperatively and/or interactively.
Ultrasound is sound with a frequency greater than the upper limit of human hearing, approximately 20 kilohertz/20,000 Hertz. Some animals, such as dogs, dolphins, bats, and mice have an upper limit that is greater than that of the human ear and thus can hear ultrasound.
Ultrasound has industrial and medical applications. Medical Sonography (also called ultrasonography) can visualize muscle and soft tissue, making them useful for scanning the organs, and obstetric sonography is commonly used during pregnancy. The use of microbubble contrast media in medical sonography to improve ultrasound signal backscatter is known as contrast enhanced ultrasound. This technique is currently used in echocardiography, and may have future applications in molecular imaging and drug delivery.
Diagnostic Sonography is often incorrectly referred to as "ultrasound"; however, ultrasound is a term of physics meaning acoustic energy with a frequency above human hearing. To call a sonogram an “ultrasound” is analogous to calling a photograph a "light". There are other uses of ultrasound in medicine that are not imaging or sonography. These include heating tissue in physical therapy, cleaning teeth in dental hygiene. Ultrasound is also used by iron workers for nondestructive testing of metals and welds, and jewelers use ultrasound to clean rings and watches. These other uses are not included in the definition of Diagnostic Sonography.
In medical ultrasonography, a sound wave is produced by creating short, strong pulses of sound from a phased array of piezoelectric transducers. The sound wave, which is able to penetrate bodily fluids, but not solids, bounces off the solid object and returns to the Transducer, this return is an echo.
The return of the sound wave to the Transducer results in the same process that it took to send the sound wave, just in reverse. The return sound wave vibrates the Transducer and turns that vibration into an electrical pulse that is sent through the probe and into sonographers computer where it can be interpreted and transformed into a digital image.
An X-ray is a form of electromagnetic radiation with a wavelength in the range of 10 nanometers to 100 picometers (corresponding to frequencies in the range 30 PHz to 3 EHz). X-rays are primarily used for diagnostic medical imaging and crystallography. X-rays are a form of ionizing radiation and as such can be dangerous.
In most languages it is called Röntgen radiation (or an equivalent name) after its discoverer Wilhelm Röntgen.
Since Röntgen's discovery that X-rays can identify bony structures, X-rays have been developed for their use in medical imaging. Radiology is a specialized field of medicine that employs radiography and other techniques for diagnostic imaging. Indeed, this is probably the most common use of X-ray technology.
The use of X-rays are especially useful in the detection of pathology of the skeletal system, but are also useful for detecting some disease processes in soft tissue. Some notable examples are the very common chest X-ray, which can be used to identify lung diseases such as pneumonia, lung cancer or pulmonary edema, and the abdominal X-ray, which can detect ileus (blockage of the intestine), free air (from visceral perforations) and free fluid (in ascites). In some cases, the use of X-rays is debatable, such as gallstones (which are rarely radiopaque) or kidney stones (which are often visible, but not always). Also, traditional plain X-rays pose very little use in the imaging of soft tissues such as the brain or muscle. Imaging alternatives for soft tissues are computed axial tomography (CAT or CT scanning), magnetic resonance imaging (MRI) or ultrasound.
A MUGA scan (Multiple Gated Acquisition Scan) is a noninvasive nuclear medicine test to evaluate the function of the heart. It provides a movie-like image of the beating heart, and allows the doctor to determine the health of the heart’s major pumping chambers.
To perform the test, stannous (Tin) ions are injected into the patient's bloodstream. The stannous ions make the red blood cells 'sticky' and a subsequent intravenous injection of the radioactive substance, Technetium-99m-pertechnetate, labels the red blood cells in-vivo. With an administered activity of about 800 MBq, the effective radiation dose is about 8 mSv. The patient is placed under a gamma camera, which detects the low-level gamma radiation being given off by technetium-99m. As the gamma camera images are acquired, the patient's heartbeat is used to 'gate' the acquisition. The final result is a series of images of the heart (usually sixteen), one at each stage of the cardiac cycle.
The resulting images show the blood pool in the chambers of the heart and the images can be analyzed on a computer to calculate the ejection fraction of the heart together with other useful clinical parameters. This scan gives an accurate and reproducible means of measuring and monitoring the ejection fraction of the left ventricle.
For a patient that has had a heart attack, or is suspected of having another disease that affects the heart muscle, this scan can help pinpoint the position in the heart that has sustained damage as well as assess the degree of damage.
It is a minimally invasive diagnostic medical procedure used to evaluate the interior surfaces of an organ by inserting a small scope in the body, often but not necessarily through a natural body opening. Through the scope, one is able to see lesions.
An instrument may not only provide an image but also enable taking small biopsies and retrieve foreign objects. Endoscopy is the vehicle for minimally invasive surgery.
Many endoscopic procedures are relatively painless and only associated with mild discomfort, though patients are sedated for most procedures. Complications are rare but may include perforation of the organ under inspection with the endoscope or biopsy instrument. If this occurs, surgery may be required to repair the injury.
· The gastrointestinal tract (GI tract):
Esophagus, stomach and duodenum (esophagogastroduodenoscopy)
Colon (colonoscopy), the endoscope is used to examine the colon.
Sigmoid colon: (proctosigmoidoscopy)
· In an endoscopic retrograde cholangiopancreatography (ERCP), an endoscope is used to introduce radiographic contrast medium into the bile ducts so they can be visualized on x-ray.
· The respiratory tract
· The nose (rhinoscopy)
· The lower respiratory tract (bronchoscopy)
· The urinary tract (cystoscopy)
· The female reproductive system
· The uterus (hysteroscopy)
· The Fallopian tubes (Falloscopy)
· Normally closed body cavities (through a small incision):
· The abdominal or pelvic cavity (laparoscopy)
· The interior of a joint (arthroscopy)
· Organs of the chest (thoracoscopy and mediastinoscopy)
· During pregnancy
· The amnion (amnioscopy)
· The fetus (fetoscopy)
In medicine (gastroenterology), esophagogastroduodenoscopy (EGD) or upper endoscopy is a diagnostic endoscopic procedure that visualizes the upper part of the gastrointestinal tract. It is considered a minimally invasive procedure since it does not require an incision into one of the major body cavities and does not require any significant recovery after the procedure (unless sedation or anesthesia has been used).
In most patients an unexplained drop in hematocrit (a sign of anemia) is an indication to do an EGD, usually along with a colonoscopy. Even if no obvious blood has been seen in the sputum (spit) or stool (feces). An EGD is most important when there are signs of an upper gastrointestinal bleed (UGI bleed). UGI bleeding often presents with melena (very dark black, tarry-like stool, which often has a foul odor). Other indications include reflux disease (also called heartburn or GERD), or blood in vomitus. Chronic acid reflux can cause changes in the cells lining the esophagus, a condition called Barrett's Esophagus, which can occasionally progress to cancer if not treated. Therefore chronic reflux is also an indication for EGD.
In its most basic use, the endoscope is used to inspect the lining of the digestive tract. Often inspection alone suffices to diagnose a patient's problem, but biopsy is a very valuable adjunct to endoscopy. Small biopsies can be made with a pincer (biopsy forceps) that is passed through the scope and allows sampling of 1 to 3 mm pieces of tissue under direct vision. The intestinal mucosa heals quickly from such biopsies.
Additional procedures that can be done include:
· Injection of liquids through a needle (e.g. Adrenalin in bleeding lesions)
· Cutting off of larger pieces of tissue with a snare (e.g. Polyps)
· Application of cautery to tissues
· Retrieval of foreign bodies that have been ingested
· Tamponading bleeding esophageal varices with a balloon
· Some surgical procedures can be done through the endoscope including tightening of the muscles at the end of the esophagus (the lower esophageal sphincter) and rubber band ligation of esophageal and gastric blood vessels.
Colonoscopy is the minimally invasive endoscopic examination of the large colon and the distal part of the small bowel with a fiber optic camera on a flexible tube passed through the anus. It may provide a visual diagnosis (e.g. ulceration, polyps) and grants the opportunity for biopsy of suspected lesions. Virtual colonoscopy, which uses 3D imagery reconstructed from computed tomography (CAT) scans, is also possible, as a totally non-invasive medical test, although it is not standard and still under investigation. Colonoscopy is similar but not the same as sigmoidoscopy. The difference between colonoscopy and sigmoidoscopy is related to which parts of the colon each can examine. Sigmoidoscopy allows doctors to view only the final part of the colon, while colonoscopy allows a complete examination of the colon.
Indications for colonoscopy include gastrointestinal hemorrhage, unexplained changes in bowel habit or suspicion of malignancy. Colonoscopies are often used to diagnose or rule out colon cancer, but are also frequently used to diagnose inflammatory bowel disease.
The days prior to the colonoscopy the patient is given a laxative preparation (such as sodium picosulfate, sodium phosphate solution, or a solution of polyethylene glycol and electrolytes) and large quantities of fluid and a low fibre or clear fluid only diet.
A very small proportion of patients suffer from perforation. This is a medical emergency and may require immediate surgery. Post colonoscopy bleeding and sedation reactions are also possible side effects.
Endoscopic Retrograde Cholangiopancreatography
Endoscopic retrograde cholangiopancreatography (ERCP) is endoscopy of the biliary tree and the pancreatic duct. By injection of contrast media, a retrograde image of both structures can be formed on X-ray, facilitating the diagnosis of obstruction, e.g. by gallstones or cholangiocarcinoma.
The patient is often sedated or anesthetized. Then a flexible camera (endoscope) is inserted through the mouth, down the esophagus, into the stomach, through the pylorus into the duodenum where the ampulla of Vater (the opening of the common bile duct) exists. The sphincter of Oddi is a muscular valve that controls the opening of the ampulla. The region can be directly visualized with the endoscopic camera while various procedures are performed. A plastic catheter or cannulatome is inserted through the ampulla, and radiocontrast is injected into the bile ducts, and/or, pancreatic duct. Fluoroscopy is used to look for blockages, or leakage of bile into the peritoneum (the abdominal cavity).
A wire and balloon may be passed into the bile duct, then inflated in order to expand the opening of the bile duct to allow passage of gallstones. Occasionally, an electric cauterizer will be used to cut the sphincter opening, making it wider.
Other procedures associated with ERCP include the trawling of the common bile duct with a basket or balloon to remove gallstones and the insertion of a plastic stent to assist the drainage of bile.
Potential complications include acute pancreatitis and perforation.
In medicine, bronchoscopy is the visualization of the lower airways using a flexible or rigid endoscope. Bronchoscopy is often performed for diagnostic purposes (diagnosis of tumor, bleeding, infection, or trauma). The diagnostic procedure of bronchoalveolar lavage is also performed by bronchoscopy. It is also useful in the treatment of airway obstruction by tumors or foreign bodies, for removal of secretions and as an assistive technique in difficult intubation of the trachea.
There are two types of bronchoscopes: flexible (fiberoptic) and rigid. Flexible bronchoscopy is often performed under local anesthesia with the patient awake. Rigid bronchoscopes may be employed to remove foreign bodies or to place stents. Such procedures are done under general anesthesia.
Endoscopy of the urinary bladder via the urethra is called cystoscopy. Diagnostic cystoscopy is usually carried out with local anaesthesia. General anaesthesia is sometimes used for operative cystoscopic procedures. When a patient has a urinary problem, the doctor may use a cystoscope to see the inside of the bladder and urethra.
A doctor may recommend cystoscopy for any of the following conditions:
· Frequent urinary tract infections
· Blood in the urine (hematuria)
· Loss of bladder control (incontinence) or overactive bladder
· Unusual cells found in urine sample
· Need for a bladder catheter
· Painful urination, chronic pelvic pain, or interstitial cystitis
· Urinary blockage such as prostate enlargement, stricture, or narrowing of the urinary tract
· Stone in the urinary tract
· Unusual growth, polyp, tumor, or cancer
Hysteroscopy is the inspection of the uterine cavity by endoscopy. It allows for the diagnosis of intrauterine pathology and serves as a method for surgical intervention (operative hysteroscopy).
Hysteroscopy is useful in a number of uterine conditions:
· Polyp (medicine)
· Asherman syndrome
· Gynecologic bleeding
· Uterine malformations
Arthroscopy (also called arthroscopic surgery) is a minimally invasive surgical procedure in which a physical examination of the interior of a joint is performed using an arthroscope, a type of endoscope that is inserted into the joint through a small incision.
The advantage over traditional knee endoscopies is that only small incisions need to be made, and the joint does not have to be opened up fully. This reduces the recovery time of the patient and may increase the rate of surgical success due to less trauma to the connective tissue. It is especially useful for professional athletes, who frequently injure knee joints and require fast healing time.
Laparoscopic surgery, also called keyhole surgery (when natural body openings are not used), Band-Aid surgery, or minimally invasive surgery (MIS), is a surgical technique. Medically, laparoscopic surgery refers only to operations within the abdomen or pelvic cavity. Laparoscopic surgery belongs to the field of endoscopy.
This approach is intended to minimize operative blood loss and postoperative pain, and speeds up recovery times.
What is barium?
Barium is a white liquid that shows up clearly on an X-ray. Once it is inside you, it coats the inside of the gullet, stomach or bowel. And so it shows up the outline of the organs on the X-ray. If there is a tumour, it will show up as an irregular outline extending out from the wall of the affected body organ.
Barium does not do you any harm and passes through your digestive system. A barium swallow may make you feel sick. Over the couple of days following the test, the barium may cause
· Mild constipation
· White stools the first couple of times you go to the toilet
A barium swallow is an x-ray of the throat and esophagus, the tube connecting the throat to the stomach. Barium blocks x-rays so that the outline of the throat and esophagus will show up on the film. The pictures are used to help pinpoint your problem.
A barium meal is a procedure in which barium sulfate is ingested by a patient and, in conjunction with X-rays, images depicting the digestive system: the distal esophagus, stomach and duodenum, are obtained. There are two varieties of barium meal, these being single and double contrast meals. A single contrast meal uses only barium to image the upper gastrointestinal tract while a double contrast meal uses barium as well as air. The double contrast meal has the advantage of demonstrating mucosal details and so is much more useful as a diagnostic test allowing the detection of small mucosal lesions.
A barium enema, also called a lower gastrointestinal series, is a medical procedure used to examine and diagnose problems with the human large intestines. An X-ray examination of the large intestines, pictures are taken after rectal instillation of barium sulfate.
This test may be done in an office or a hospital radiology department. The patient lies on the X-ray table and a preliminary X-ray is taken. The patient is then asked to lie on the side while a well-lubricated enema tube is inserted gently into the rectum. The barium, a radiopaque (shows up on X-ray) contrast medium, is then allowed to flow into the colon. A small balloon at the tip of the enema tube may be inflated to help keep the barium inside. The flow of the barium is monitored by the health care provider on an X-ray fluoroscope screen (like a TV monitor). Air may be puffed into the colon to distend it and provide better images.
The patient is usually asked to move to different positions and the table is slightly tipped to get different views.
If a double or air - contrast examination is being done, the enema tube will be reinserted gently and a small amount of air will be gently introduced into the colon, and more X-ray pictures are taken.
Barium should fill the colon uniformly and show normal bowel contour, patency (should be freely open), and position.
Abnormal findings may include cancer, diverticulitis (small pouches formed on the colon wall that can become inflamed), polyps (a tumor, usually noncancerous, that grows on the mucous membrane), inflammation of the inner lining of the intestine (ulcerative colitis), and irritable colon. An acute appendicitis or twisted loop of the bowel may also be seen.
Pap smear (pap is an abbreviation for Papanicolaou), as it is currently known (smear test in some countries), is an invention of Dr. Georgios Papanicolaou (1883-1962), an American of Greek birth, the father of cytopathology. The test is simple and effective, consisting of a simple cervical swab to collect a sampling of cells. These cells are placed on a glass slide and checked for abnormalities in the laboratory. Approximately five to seven percent of pap smears produce abnormal results, such as dysplasia, a possibly pre-cancerous condition. Many of these abnormalities are not due to cervical cancer, but they are an indicator that increased vigilance is needed.
Flow cytometry is a technique for counting, examining and sorting microscopic particles suspended in a stream of fluid. It allows simultaneous multiparametric analysis of the physical and/or chemical characteristics of single cells flowing through an optical/electronic detection apparatus.
Modern flow cytometers can analyse several thousand particles every second in "real time" and can actively separate out and isolate particles having specified properties. A flow cytometer is similar to a microscope, except it doesn't produce an image of the cell but offers high-throughput automated quantification of the set parameters for high number of single cells during each analysis session.
The data coming from flow-cytometers can be plotted in 1-D to produce histograms or seen in 2D as dot plots or in 3D with newer software and then studied.
Intravenous Pyelogram (IVP)
An intravenous pyelogram (also known as IVP, pyelography, intravenous urogram or IVU) is a radiological procedure used to visualize disturbances of the urinary system, including the kidneys, ureters, and bladder. Among other uses, IVP can detect kidney stones.
It is done as a series of X-rays before and after a contrast agent (dye) is injected into a vein. This contrast is removed from the blood by the kidneys at a predictable time, where they initially appear opaque on X-ray film early after injection, followed by the appearance of iodinated contrast in the urine which outlines the renal calyces, ureters and bladder in the later X-rays in the series. Finally the bladder is imaged while filled and then after emptying, allowing assessment of any unseen abnormalities and completeness of voiding. It has to be differentiated from KUB.
In medicine, KUB refers to a diagnostic medical imaging technique and stands for Kidneys, Ureters, and Bladder.
A KUB is a plain frontal supine radiograph of the abdomen. It is often supplemented by an upright PA view of the chest (to rule out air under the diaphragm or thoracic etiologies presenting as abdominal complaints) and a standing view of the abdomen (to differentiate obstruction from ileus by examining gastrointestinal air/water levels).
Despite its name, a KUB is not typically used to investigate pathology of the kidneys, ureters, or bladder, since these structures are difficult to assess (for example, the kidneys may not be visible due to overlying bowel gas.) In order to assess these structures with X-ray, a technique called an intravenous pyelogram is utilized.
KUB is typically used to investigate gastrointestinal conditions such as a bowel obstruction and gallstones, and can detect the presence of kidney stones.
Mammography is the process of using low-dose X-rays (usually around 0.7 mSv) to examine the human breast. It is used to look for different types of tumors and cysts. Only mammography has been proven to reduce mortality from breast cancer. In some countries routine (annual to five-yearly) mammography of older women is encouraged as a screening method to diagnose early breast cancer.
At this stage mammography is still the modality of choice for screening of early breast cancer. It is the gold-standard for other imaging methods such as ultrasound and NMR-tomography. CT has no real role in diagnosing breast cancer at the present. Ultrasound is useful as an adjunct to mammography in some cases, as is Magnetic resonance imaging, but neither should be used as a screening method. Only Mammography has been proven useful for screening.
HIV Tests (AIDS Tests)
HIV test kits used both to screen donor blood, blood components and cellular products, and to diagnose, treat and monitor persons with HIV and AIDS are regulated in the United States by the FDA.
HIV tests to detect antibodies, antigens or RNA in serum, plasma, oral fluid, dried blood spot or urine have been approved by FDA for donor screening, diagnosis, prognosis and patient monitoring.
The window period is the time from infection until a test can detect any change. The average window period with antibody tests is 22 days. Antigen testing cuts the window period to approximately 16 days and NAT further reduces this period to 12 days.
Antibody tests are specifically designed for the routine testing of HIV in adults, are inexpensive, and are very accurate. If a person does not have a realistic risk of infection, then these tests are not necessary. Antibody tests give false negative results during the window period
The ELISA test, or the enzyme immunoassay (EIA), was the first screening test commonly employed. It has a high sensitivity. The low specificity of the test is because antibodies attach to antigens in the test kits "by accident", even though the person has never been exposed to HIV. About 80% of positive ELISA tests are followed by a negative Western-Blot test, and therefore regarded as false positive.
The Western blot test uses the general Western blot procedure. HIV-infected cells are opened and the contained proteins are entered into a slab of gel to which a voltage is applied. Different proteins will move with different velocities in this field, depending on their size, while their electrical charge is leveled by a substance, called sodium lauryl sulfate. Once the proteins are well separated, they are transferred to a membrane and the procedure continues similar to ELISA.
Rapid or point-of-care tests
Rapid Antibody Tests are qualitative immunoassays intended for use as a point-of-care test to aid in the diagnosis of HIV infection. These tests should be used in conjunction with the clinical status, history, and risk factors of the person being tested. The specificity of Rapid Antibody Tests for in low-risk populations has not been evaluated.
OraQuick is an antibody test that provides results in 20 minutes. The blood, plasma or oral fluid is mixed in a vial with developing solution, and the results are read from a stick-like testing device.
OraSure is an HIV test, which uses mucosal transudate from the tissues of cheeks and gums. It is an antibody test, which first employs ELISA, then Western Blot.
There is also a urine test; it employs both the ELISA and the Western Blot method.
Home Access Express HIV-1 Test is a FDA-approved home test: the patient collects a drop of blood and mails the sample to a laboratory; the results are obtained over the phone.
The p24 antigen test detects the presence of the p24 protein of HIV (also known as CA), a major core protein of the virus.
Nucleic acid based tests
Nucleic acid based tests amplify and detect a 142 base target sequence located in a highly conserved region of the HIV gag gene.
In the RT-PCR test, the viral RNA is extracted from the patient's plasma and is treated with reverse transcriptase so that the RNA of the virus is transcribed into DNA.
In the Quantiplex bDNA or branched DNA test plasma is centrifugated to concentrate the viruses, which are then opened to release the RNA.
CD4 count significance
The CD4 T-cell count is not an HIV test, but rather a procedure where the number of CD4 T-cells in one microliter of blood are counted in a standard medical lab test after a blood draw.
This test does not check for the presence of HIV. It is used monitor the immune system function in HIV+ people. Declining CD4 T-cell counts are considered to be a marker of the progression of HIV infection. In HIV+ people, AIDS is officially diagnosed when the count drops below 200 cells or when certain opportunistic infections occur.
Electroencephalography is the neurophysiologic measurement of the electrical activity of the brain by recording from electrodes placed on the scalp, or in the special cases on the cortex. The resulting traces are known as an electroencephalogram (EEG) and represent so-called brain waves. This device is used to assess brain damage, epilepsy and other problems. In some jurisdictions it is used to assess brain death. EEG can also be used in conjunction with other types of neuroimaging.
Historically four major types of continuous rhythmic sinusoidal EEG waves are recognized alpha, beta, delta and theta.
The echocardiogram is an ultrasound of the heart. Using standard ultrasound techniques, two-dimensional slices of the heart can be imaged. The latest ultrasound systems now employ 3D real-time imaging.
The standard echocardiogram is also known as a transthoracic echocardiogram, or TTE. In this case, the echocardiography transducer (or probe) is placed on the chest wall (or thorax) of the subject, and images are taken through the chest wall. This is a non-invasive, highly accurate and quick assessment of the overall health of the heart. A cardiologist can quickly assess a patient's heart valves and degree of heart muscle contraction (an indicator of the ejection fraction). The TTE is a popular test, which keeps improving with more and more advances in the field.
Another method to perform an echocardiogram is to insert a specialized scope containing an echocardiography transducer (TOE probe) into the patient's esophagus, and record pictures from there. This is known as a transesophageal echocardiogram, or TEE. The advantages of TEE over TTE are clearer images, since the transducer is closer to the heart. Some structures are better imaged with the TEE. These structures include the aorta, the pulmonary artery, the valves of the heart, and the left and right atria.
An electrocardiogram (ECG or EKG) is a graphic produced by an electrocardiograph, which records the electrical voltage in the heart in the form of a continuous strip graph. It is the prime tool in cardiac electrophysiology, and has a prime function in screening and diagnosis of cardiovascular diseases.
An ECG is constructed by measuring electrical potential between various points of the body using a galvanometer. There are twelve leads in total. Each, by their nature, record information from particular parts of the heart:
· The inferior leads (leads II, III and aVF) look at electrical activity from the vantage point of the inferior region (wall) of the heart. This is the apex of the left ventricle.
· The lateral leads (I, aVL, V5 and V6) look at the electrical activity from the vantage point of the lateral wall of the heart, which is the lateral wall of the left ventricle.
· The anterior leads, V1 through V6, and represents the anterior wall of the heart, or the frontal wall of the left ventricle.
· aVR is rarely used for diagnostic information, but indicates if the ECG leads were placed correctly on the patient.
A typical ECG tracing of a normal heartbeat consists of a P wave, a QRS complex and a T wave. A small U wave is not normally visible.
The axis is the general direction of the electrical impulse through the heart. It is usually directed to the bottom left (normal axis: -30o to +90o), although it can deviate to the right in very tall people and to the left in obesity.
The P wave is the electrical signature of the current that causes atrial contraction.
The QRS complex corresponds to the current that causes contraction of the left and right ventricles, which is much more forceful than that of the atria and involves more muscle mass, thus resulting in a greater ECG deflection.
The T wave represents the repolarization of the ventricles. The QRS complex usually obscures the atrial repolarization wave so that it is not usually seen. T wave abnormalities may indicate electrolyte disturbance, such as hyperkalemia and hypokalemia.
The ST segment connects the QRS complex and the T wave.
The QT interval is measured from the beginning of the QRS complex to the end of the T wave. The QT interval as well as the corrected QT interval are important in the diagnosis of long QT syndrome and short QT syndrome. The QT interval varies based on the heart rate, and various correction factors have been developed to correct the QT interval for the heart rate.
The PR interval is measured from the P wave to the QRS complex. It is usually 0.12 to 0.20 seconds. A prolonged PR indicates a first-degree heart block, while a shorting may indicate an accessory bundle, such as seen in Wolff-Parkinson-White syndrome
A Holter monitor (also called an ambulatory electrocardiography device), named after its inventor, Dr. Norman J. Holter, is a portable device for continuously monitoring the electrical activity of the heart for 24 hours or more. Its extended recording period is useful for observing occasional cardiac arrhythmias that would be otherwise difficult to identify in a shorter period of time.
Much like standard electrocardiography (EKG), the Holter monitor records electrical signals from the heart via a series of electrodes attached to the chest. The number and position of electrodes varies by model, but most Holter monitors employ from three to seven. Typical devices use a standard C60 or C90 audio cassette run at a very slow speed to record the data. More modern units record onto digital flash memory devices. The data is uploaded into a computer which then automatically analyses the input, counting ECG complexes, calculating summary statistics such as average heart rate, minimum and maximum heart rate, and finding candidate areas in the recording worthy of further study by the technician.
Single Photon Emission Computed Tomography
SPECT (Single Photon Emission Computed Tomography) is a nuclear medicine tomographic imaging technique using gamma rays. The technique results in a set of image slices through a patient, showing the distribution of a radiopharmaceutical like Technetium-99m.
Genetic testing allows the genetic diagnosis of vulnerabilities to inherited diseases, and can also be used to determine a person's ancestry. Every person carries two copies of every gene, one inherited from their mother, one inherited from their father. The human genome is believed to contain about 25,000 genes. In addition to studying chromosomes to the level of individual genes, genetic testing in a broader sense includes biochemical tests for the presence or absence of key proteins that signal aberrant genes.
Genetic testing usually involves examining a person's DNA - taken from cells in a sample of blood or, occasionally, from other body fluids or tissues - for some anomaly that flags a disease or disorder. The DNA change can be relatively large: a missing or added piece of a chromosome - even an entire chromosome - that is visible under a microscope. Or it can be extremely small, as little as one extra, missing, or altered chemical base.
Genetic testing can provide only limited information about an inherited condition. The test often can't determine if a person will show symptoms of a disorder, how severe the symptoms will be, or whether the disorder will progress over time. Another major limitation is the lack of treatment strategies for many genetic disorders once they are diagnosed.
Tumor Marker Tests
Tumor markers are specific substances found in the blood, urine or body tissues that arise from cells and are often elevated in cancer. These markers are either produced by the tumor, are elevated because of the tumor’s effect on cells around it or are produced in response to the tumor.
The first marker groups are related to the presence of cancerous tissue, and unfortunately these markers tend to be very unhelpful in making a diagnosis (because there is a large overlap between the many different tumor types and the markers produced). They can, however, be useful in follow up of treated patients to describe progress of the disease before any further masses can be found clinically or by imaging. A few examples of these markers are CEA, CA19-9, and CA125.
CEA, or carcinoembryonic antigen, is a blood-borne protein, first noted to be produced by tumors of the gastrointestinal system.
PSA or Prostate specific antigen is produced by the normal prostate gland. It is a protein enzyme called a serine protease that usually acts as an anticoagulant to keep semen liquid. Only small amounts leak into the circulation in normal circumstances. Enlarged prostates leak more substantial amounts and cancerous prostates also leak substantial amounts thereby raising the PSA level.
Blood tests are laboratory tests done on blood to gain an appreciation of disease states and the function of organs. Since blood flows throughout the body, acting as a medium for providing oxygen and other nutrients, and drawing waste products back to the excretory systems for disposal, the state of the bloodstream affects, or is affected by, many medical conditions. For these reasons, blood tests are the most commonly performed medical tests. Blood is obtained from a patient by venipuncture, except for tests such as Arterial blood gas.
Blood is useful, as it is a relatively non-invasive way to obtain cells, and extracellular fluid (plasma), from the body to check on its health. Although the term blood test is used, most routine tests (except for most hematology) are done on plasma or serum.
The list below includes both specific tests, and general techniques.
The CHEM-7 test is a battery of blood chemistry tests. The seven parts of a CHEM-7 include tests for:
Blood chemistry tests
Bicarbonate or co2 
Blood urea nitrogen (bun) 
Glucose . (This test can also be performed directly by diabetic patients by using a glucose meter.)
Large organic molecules
Protein electrophoresis (general technique -- not a specific test)
Western blot (general technique -- not a specific test)
Liver function tests
Serology (general technique -- not a specific test)
Wassermann test (for syphilis)
Cold agglutinins test 
Polymerase chain reaction (DNA). DNA testing is today possible with even very small quantities of blood: this is commonly used in forensic science, but is now also part of the diagnostic process of many disorders.
Northern blot (RNA)
CBC or Full blood count (or "complete blood count")
Hematocrit and MCV ("mean corpuscular volume")
Erythrocyte sedimentation rate (ESR)
Cross-matching-Determination of blood type for blood transfusion or transplants
Blood cultures are commonly taken if infection is suspected. Positive cultures and resulting sensitivity results are often useful in guiding medical treatment.
Complete Blood Count
A complete blood count (CBC) or full blood count (FBC) is a test requested by a doctor or other medical professional that gives information about the cells in a patient's blood. A CBC is also known as a "hemogram".
A complete blood count will normally include:
· Total red blood cells - The number of red cells is given as an absolute number per litre.
· Hemoglobin - The amount of hemoglobin in the blood, expressed in grams per litre. (Low hemoglobin is called anemia.)
· Hematocrit or packed cell volume (PCV) - This is the fraction of whole blood volume that consists of red blood cells.
· Mean cell volume (MCV) - the average volume of the red cells. Anemia is classified as microcytic or macrocytic based on whether this value is above or below the expected normal range. Other conditions that can affect MCV include thalassemia and reticulocytosis.
· Mean cell hemoglobin (MCH) - the average amount of hemoglobin per red blood cell, in picograms.
· Mean cell hemoglobin concentration (MCHC) - the average concentration of hemoglobin in the cells.
· Red blood cell distribution width (RDW) - a measure of the variation of the RBC population
Total white blood cells - All the white cell types are given as a percentage and as an absolute number per litre.
A complete blood count with differential will also include:
· Neutrophil granulocytes - May indicate bacterial infection. May also be raised in acute viral infections.
· Lymphocytes - Higher with some viral infections such as glandular fever and. Also raised in lymphocytic leukemia, CLL.
· Monocytes - May be raised in bacterial infection
· Eosinophil granulocytes - Increased in parasitic infections.
· Basophil granulocytes
· A manual count will also give information about other cells that are not normally present in peripheral blood, but may be released in certain disease processes.
Platelet numbers are given, as well as information about their size and the range of sizes in the blood.
Liver Function Tests
Liver function tests (LFTs or LFs) are groups of clinical biochemistry laboratory blood assays designed to give a doctor or other health professional information about the state of a patient's liver. Most liver diseases cause only mild symptoms initially, while it is vital that these diseases are detected early. Hepatic involvement in some diseases can be of crucial importance.
Regular liver panel would include:
Total Protein (TP)
The liver produces most of the plasma proteins in the body making a measure of the amount of protein in the blood useful. Reference range is 60-80 g/L.
Albumin is a protein made specifically by the liver, and can be measured cheaply and easily. It is the main constituent of total protein; the remaining fraction is called globulin (including e.g. the immunoglobulins). Albumin levels are decreased in chronic liver disease, such as cirrhosis. It is also decreased in nephrotic syndrome, where it is lost through the urine. Poor nutrition or states of protein catabolism may also lead to hypoalbuminemia. The reference range is 30-50 g/L. (3.0-5.0 mg/dL).
Alanine transaminase (ALT)
Alanine transaminase (ALT), also called Serum Glutamic Pyruvic Transaminase (SGPT) or Alanine aminotransferase (ALAT) is an enzyme present in hepatocytes (liver cells). When a cell is damaged, it leaks this enzyme into the blood, where it is measured. ALT rises dramatically in acute liver damage, such as viral hepatitis or paracetamol (acetaminophen) overdose. The reference range is 15-45 U/L in most laboratories.
Alkaline phosphatase (ALP)
Alkaline phosphatase (ALP) is an enzyme in the cells lining the biliary ducts of the liver. If there is an obstruction in the bile duct, e.g. gallstones, ALP levels in plasma will rise. ALP is also present in bone and placental tissue, so it is higher in growing children (as their bones are being remodeled). The reference range is usually 30-120 U/L.
Total bilirubin (TBIL)
Bilirubin is a breakdown product of heme (a part of hemoglobin in red blood cells). The liver is responsible for clearing this, excreting it out through bile into the intestine. Problems with the liver or blockage of the drainage of bile will cause increased levels of bilirubin, as will increased hemolysis of red cells.
Other tests commonly requested alongside LFTs:
Aspartate transaminase (AST)
Aspartate transaminase (AST) also called Serum Glutamic Oxaloacetic Transaminase (SGOT) or aspartate aminotransferase (ASAT) is similar to ALT in that it is another enzyme associated with liver parenchymal cells. It is raised in acute liver damage. It is also present in red cells and cardiac muscle.
Gamma glutamyl transpeptidase (GGT)
Although reasonably specific to the liver and a more sensitive marker for cholestatic damage than ALP, Gamma glutamyl transpeptidase (GGT) may be elevated with even minor, sub-clinical levels of liver dysfunction. It can also be helpful in identifying the cause of an isolated elevation in ALP. GGT is raised in alcohol toxicity (acute and chronic).
Coagulation tests (e.g. INR)
The liver is responsible for the production of coagulation factors. The international normalized ratio (INR) measures the speed of a particular pathway of coagulation, comparing it to normal. If the INR is increased, it means it is taking longer than usual for blood to clot. The INR will only be increased if the liver is so damaged.
The INR is the ratio of a patient's prothrombin time to a normal (control) sample, raised to the power of the ISI value for the control sample used.
The prothrombin time (PT) and its derived measures of prothrombin ratio (PR) and international normalized ratio (INR) are measures of the extrinsic pathway of coagulation. They are used to determine the clotting tendency of blood, in the measure of warfarin dosage, liver damage and vitamin K status. The reference range for prothrombin time is 12 - 15 seconds; the range for the INR is 0.8-1.2.
Radioimmunoassay is a scientific method used to test hormone levels in the blood without the need to use a bioassay. It involves mixing a radioactive antigen (frequently labeled with isotopes of iodine attached to tyrosine) with antibody to that antigen, then adding unlabeled or "cold" antigen in known quantities and measuring the amount of labeled antigen displaced.
The Mantoux test (or Mantoux screening test, Tuberculin Sensitivity Test, Pirquet test, or PPD test for Purified Protein Derivative) is a diagnostic tool for tuberculosis.
A standard dose of 10 Tuberculin units (0.2 ml) is injected intradermally (into the skin) and read 48 to 72 hours later. A person who has been exposed to the bacteria is expected to mount an immune response in the skin containing the bacterial proteins.
The reaction is read by measuring the diameter of induration (palpable raised hardened area) across the forearm (perpendicular to the long axis) in millimeters.
Tuberculin skin testing is not contraindicated for BCG-vaccinated persons.
The Heaf test is a diagnostic skin test performed in order to determine whether or not a child has been exposed to tuberculosis.
It is done in the United Kingdom to determine if the BCG vaccine is needed. Patients who exhibit a negative reaction may be offered BCG vaccination.
Gram staining (or the Gram's method) is an empirical method of differentiating bacterial species into two large groups (Gram-positive and Gram-negative) based on the chemical and physical properties of their cell walls.
Gram staining is one of the most useful staining procedures in bacteriological laboratory. The technique is widely used as a tool for differentiating Gram-negative and Gram-positive bacteria, as a first step to determine the identity of a particular bacterial sample.
Renal Function Tests
In medicine (nephrology) renal function is an indication of the state of the kidney and its role in physiology. Most doctors use creatinine, urea and electrolytes to determine renal function. These measures are adequate to determine whether a patient is suffering from kidney disease.
Unfortunately, BUN and creatinine will not be outside the normal range until 60% of total kidney function is lost. Hence, creatinine clearance is a more accurate measure and is used whenever renal disease is suspected or careful dosing of nephrotoxic drugs is required.
Glomerular filtration rate: In renal patients, the glomerular filtration rate (GFR) is used. This is calculated by comparing urine creatinine levels with the blood test results. It gives a more precise indication of the state of the kidneys. The GFR is expressed in ml/min. For most patients, a GFR over 60 ml/min is adequate.
Cockroft-Gault formula: A commonly used surrogate marker for actual creatinine clearance is the Cockroft-Gault formula, which employs creatinine measurements and a patient's weight to predict the clearance.
MDRD formula: The most recently advocated formula for calculating the GFR is the one that was developed as a result of the Modification of Diet in Renal Disease (MDRD) study.
Children: Schwartz: In children, the Schwartz formula is used. This employs the serum creatinine, the child's height and a constant to estimate the creatinine clearance.
Creatinine clearance is a method that estimates the glomerular filtration rate (GFR) of the kidneys.
Creatinine clearance is the amount of creatinine in the urine, divided by the concentration in the blood, over a certain amount of time.
Glomerular filtration rate can be calculated by measuring any chemical that has a steady level in the blood, and is filtered but neither actively absorbed or excreted by the kidneys. Creatinine is used because it fulfills these requirements (though not perfectly), and it is produced naturally by the body. Other methods involve constant infusions of inulin or another compound, to maintain a steady state in the blood.
All Diagnostic Tests