Specific Tests

Hundreds of different medical tests exist. Some tests are performed so often that it almost seems odd to find an older person who has not undergone such a test at least once. Other tests are done so infrequently that most people will never have them done. But many tests, because they fall somewhere in between, are likely to generate questions. Several such tests are discussed below.

Bone Densitometry

Other names: Dual-energy x-ray absorptiometry (DEXA).

Related tests: Closely related bone densitometry tests include single- or dual-energy photon absorptiometry and single-energy x-ray absorptiometry.

Why the test is done: Bone densitometry measures bone density to determine whether a person has or is at high risk of developing osteoporosis. In osteoporosis, porous (less dense) bones are weak and more likely to break. Certain bones, including those of the hip, spine, and wrist, are especially likely to become porous and warrant particular attention.

How the test is done: A bone densitometry scanner analyzes changes in x-ray beams as they pass through the body. These changes are then analyzed to calculate bone density.

See the figure Assessing the Density of Bones.

Preparing for the test: Minimal preparation is needed. The person is usually instructed to wear comfortable, loose-fitting clothes that are free of buttons, snaps, zippers, and wire supports. Medications are not affected by the test and need not be changed.

What to expect during the test: The person is helped onto a special table and is instructed to lie flat. A scanner is then positioned overhead. The technician remains in the room while the test is underway. The person can hear soft buzzing and can watch the scanner as it changes positions to obtain views of specific bones. The test usually lasts about 10 to 20 minutes.

Most people find the test to be simple and painless. People who find it difficult to lie flat, such as those with arthritis or chronic obstructive pulmonary disease (COPD), may experience discomfort.

What to expect after the test: Usual activities can be resumed immediately after the test is finished.

Potential problems: Bone densitometry is very safe. The small amount of radiation the person is exposed to is less than that from a simple chest x-ray.

Results in older people: Test results may be more difficult to interpret. Osteoarthritis, accumulation of calcium in ligaments, or a history of broken bones (especially in the spine, a site that often receives particular attention during the test) can interfere with the determination of bone density.

Computed Tomography (CT)

Other names: Computed axial tomography (CAT).

Why the test is done: A CT scan is done to provide images of the body's interior for the purpose of detecting structural abnormalities, such as tumors, dead tissue (infarctions), or infected tissue that cannot be seen on simple x-rays. In some instances, a CT scan assists a doctor in guiding a hollow needle into abnormal growths or tissue inside the body so that a sample can be obtained for examination.

How the test is done: Continuous x-rays are taken by a moving part of the CT scanner. The scanner's computer then uses information on how the x-rays penetrated specific tissues to generate pictures. The detailed pictures show the body in "slices" (cross-sectional views) from head to toe (as if looking down through the head or up through the feet). Some newer scanners can create 3-dimensional images of the body. In contrast, simple x-rays view the body from front to back, back to front, or side to side. In CT scanning, sometimes a dye is injected into a vein to highlight certain structures, such as blood vessels and specific organs. Alternatively, people undergoing CT scanning of the digestive tract may be asked to swallow dye mixed in a drink.

Preparing for the test: The person is asked to wear comfortable, loose-fitting clothing free of buttons, snaps, zippers, and wire supports. When use of a dye is planned, the person is asked about allergies to the dye. If a dye is to be injected or swallowed, the person is asked to refrain from eating for several hours and from drinking for at least 1 hour before the test. Most medications are not affected by the test and need not be changed. Metformin, a drug for diabetes, can be harmful if dye is used.

What to expect during the test: The person is asked to remove any jewelry that might interfere with the quality of the pictures. The person lies flat on a motorized scanner table. If dye is to be injected, an intravenous line is inserted. If dye is to be swallowed, a drink containing the dye is provided. Once the person is properly positioned, the table moves into a large tube that contains the x-ray device. The tube then rotates around the person, taking multiple pictures. With older scanners, the test may take 10 to 20 minutes, depending on how much of the body is being scanned. With newer scanners (helical, or spiral, scanners; high-speed multi-slice scanners), the table moves quickly and steadily through the tube. A complete scan of the entire body may take less than a minute.

Most people find the test to be simple and painless. However, a few experience discomfort, especially those who find it difficult to lie flat. Occasionally, people who fear being in a confined space (claustrophobia) may be uncomfortable during a CT scan of the head or upper body. When the test involves injection of a dye, the person may experience a brief sensation of warmth and a metallic taste.

What to expect after the test: Usual activities can be resumed immediately after the test. If dye has been used, usually the person is advised to drink extra fluids for the rest of the day.

Potential problems: The amount of radiation to which the person is exposed, although more than that from a simple chest x-ray, is still considered to be safe. Uncommonly, a person has an allergic reaction to the dye.

Magnetic Resonance Imaging (MRI)

Other names: Magnetic resonance scanning.

Why the test is done: An MRI scan is done to provide images of the body's interior for the purpose of detecting abnormalities, such as tumors and dead or infected tissue, that cannot be seen on simple x-rays.

How the test is done: An MRI scanner, which is a large magnet, produces a magnetic field. The magnetic field causes certain molecules within the person's body to undergo a very brief change. Radio waves are then passed through the body. A computer creates detailed pictures using information about how the radio waves were affected by different tissues and structures. The pictures show the body in "slices" (cross-sectional views) from head to toe (as if looking down through the head or up through the feet), from side to side, and from front to back. A dye is sometimes injected into a vein to highlight certain structures, such as blood vessels and specific organs.

The strength of the magnetic field makes undergoing an MRI unsafe for people with certain electronic or metallic materials in their body, such as pacemakers, cochlear implants, and clips used to repair blood vessels. People who have had recent surgery should not undergo an MRI scan.

Preparing for the test: The person is asked to wear comfortable, loose-fitting clothing that is free of buttons, snaps, zippers, and wire supports. Items with magnetic strips (such as credit cards) and most kinds of metal cannot be worn or otherwise taken into the scanner room because of the effects of the strong magnet even when the machine is not scanning. Medications are not affected by the test and need not be changed.

What to expect during the test: The person lies flat on a scanner table and is told to remain as still as possible. If dye is to be injected, an intravenous line is inserted. If a closed scanner is being used, the table moves the person into a large tube that contains the magnet. In open scanners, the table is open on all four sides. The magnet is contained within an overhead arm. The scanner produces a thumping or knocking sound that can be heard while pictures are being produced. The sound from closed scanners is louder than that from open scanners. The test usually takes about 20 to 30 minutes, although some complex scans may take 45 to 60 minutes.

Most people find the test to be simple and painless. A few experience discomfort, especially those who find it difficult to lie flat. People who find the thumping or knocking sound disturbing or worrisome are usually offered ear protectors to help dampen the noise. Recordings of music or soothing sounds may also help the person relax. People who fear being in a confined space (claustrophobia) may be uncomfortable in a closed scanner. An open scanner may be an alternative, or a drug may be given to help reduce or control anxiety.

What to expect after the test: Usual activities can be resumed immediately after the test.

Potential problems: MRI scanning is very safe. Rarely, a person has an allergic reaction to the dye.

Positron Emission Tomography (PET)

Other names: None.

Why the test is done: Most often, a PET scan of the entire body is done to detect cancer, to determine if cancer has spread, or to monitor how well cancer is responding to treatment. Sometimes a PET scan is done to determine how well a part of the body, such as the brain or heart, is functioning. The test can also measure blood flow. These results help detect tissue that has been damaged by a disease or an injury.

How the test is done: A substance that is known to be used by specific cells or tissues in the body, such as glucose, is attached to radioactive material. A small amount of this combination is then injected into the blood. The radioactive material gives off particles, called positrons, which can be measured with a special detecting instrument. Abnormal areas are then displayed. Some devices combine PET scanning and CT scanning to produce cross-sectional (slices as if looking down through the head or up through the feet) or 3-dimensional views.

Preparing for the test: The person is asked to wear comfortable, loose-fitting clothing. For about 24 hours before undergoing a PET scan of the brain, the person is told to avoid alcohol, caffeine, and any tobacco products or drugs that might alter mental function (such as sedatives). For several hours before undergoing a PET scan that includes the abdomen, the person is asked to refrain from eating or drinking. Most medications are not affected by the test. However, the scheduling of certain drugs, for example, those used to treat diabetes, may need to be adjusted.

What to expect during the test: Before the test is started, an intravenous line is inserted so that the radioactive material can be injected. Throughout much of the test, the person lies flat. At times the person may be asked to perform certain activities, depending on the part of the body being studied. For example, if the test is measuring brain function, the person may be asked to perform mental tasks that stimulate certain parts of the brain. The test takes about 1 to 2 hours. Most people find the test to be simple and painless. A few experience discomfort, especially those who find it difficult to lie flat.

What to expect after the test: Usual activities can be resumed immediately after the test.

Potential problems: A PET scan is safe.

Nuclear Scan

Other names: Radionuclide scan.

Why the test is done: A nuclear scan may be done for a variety of reasons, depending on the type of scan. A thyroid scan is done to determine whether nodules are producing thyroid hormone. A cardiac scan is done to assess damage after a heart attack or to determine how well the heart is able to pump blood. A lung scan may be done to determine if a clot is present (pulmonary embolus) and to assess the resulting damage. A gallbladder scan is used to identify inflammation and to determine if bile is draining appropriately from the gallbladder. A renal (kidney) scan is done to identify kidney problems and disorders, including abnormal blood flow, tumors, and infections. A gallium scan (named for gallium, which is the radioactive material used in the test) is done to locate areas of infection or tumor. A bone scan is done to find cancer or infection in bones.

How the test is done: A small amount of a radioactive material is injected into the blood. The radioactivity can be measured with a special detecting scanner to determine where the radioactive material is accumulating and how long it is taking to do so. Areas of activity are used to construct images of the body.

Preparing for the test: Preparation depends on the type of scan. Many types, such as bone scans, heart scans, and gallium scans, may not require any preparation. However, before undergoing a gallbladder scan, the person is asked to refrain from eating or drinking for several hours. Generally, medications are not affected by the test. However, the scheduling of certain drugs, for example, those used to treat diabetes, may need to be adjusted.

What to expect during the test: Since radioactive material is to be injected, an intravenous line is inserted. The person lies flat on a scanner table, under the scanner and camera, and is told to remain as still as possible while a set of pictures is taken.

Some types of nuclear scans involve taking several sets of pictures over several hours to measure the accumulation of radioactive material. Picture taking is separated by periods when the person can rest or get up and move about. Each set of pictures may be completed in 20 to 30 minutes, but repeated sets can take up to 3 days to complete.

Most people find nuclear scans to be simple and painless. However, some experience discomfort, for example, because of the need to lie flat.

What to expect after the test: Usual activities can be resumed immediately after the test.

Potential problems: Nuclear scanning is safe in almost all people.

Mammography

Other names: None.

Why the test is done: A screening mammogram is done to look for evidence of breast cancer in women who do not have symptoms of breast cancer. A mammogram may also be done to further evaluate a previously identified lump.

How the test is done: Simple x-rays are taken from at least two views of each breast to generate pictures of the internal structures of the breasts.

Preparing for the test: The woman is asked not to use underarm deodorants or powders on the morning of the test, because these products can interfere with the pictures by creating the false appearance of abnormalities (artifacts). Medications do not affect the test and need not be changed.

See the figure Mammography: Screening for Breast Cancer.

What to expect during the test: The woman changes into a loose-fitting gown that opens in the front. She is then positioned next to the special x-ray unit. The technician places a flat x-ray film cassette under the breast and a flat plastic plate over the breast, compressing the breast so that an image can be taken. The woman may experience discomfort from compression of the breast. The test takes about 30 minutes.

What to expect after the test: Usual activities can be resumed immediately after the test.

Potential problems: Mammography is very safe. The small amount of radiation that the woman is exposed to does not pose a danger.

Ultrasound

Other names: Ultrasonography, Doppler.

Why the test is done: An ultrasound scan may be done for a variety of reasons. Ultrasound scanning can be used to look for abnormalities, such as tumors or areas of infection, within internal organs or structures, such as the liver, kidneys, or thyroid gland. Ultrasound scans are often done to determine how well an organ is functioning. For example, an ultrasound scan can measure how well the heart is pumping blood (echocardiogram). A special type, called a Doppler ultrasound scan, measures blood flow and can be used to determine if blood vessels are blocked.

Ultrasound scanning can be done to determine if a mass is solid, liquid, or a combination of the two. Occasionally, an ultrasound scan is done to determine if an excessive amount of urine remains in the bladder after urination. In some instances, ultrasound scanning assists a doctor in guiding a hollow needle into a growth or tissue inside the body so that a sample can be obtained for examination.

How the test is done: A handheld device called a transducer produces high-frequency sound waves. Most often, the transducer is used to pass waves through skin and muscle. When waves strike organs and abnormal growths inside the body, echoes bounce back. The echoes are captured by the transducer, and an image is produced.

The examiner applies gel to the skin over the approximate location of any organ or growth that is being examined. The gel improves the passage of sound waves through the skin. The examiner glides the transducer on the skin, over the area where the gel has been applied.

In some instances, the transducer can be passed inside the body. For example, a smaller type of transducer may be passed through the anus into the rectum for images of the prostate gland or into the vagina for images of the uterus and ovaries. Also with the use of an endoscope, a transducer can be passed through the mouth and into the bottom portion of the esophagus for images of the heart. When ultrasound involves passing the transducer through the esophagus, preparation for the test and what happens during and after the test are similar to the experience of undergoing esophagogastroduodenoscopy.

Ultrasound images can be produced continuously, usually for several minutes, so that movement can be shown, such as blood flowing through vessels or muscles contracting and relaxing. In some instances, a graph is produced to show the speed and strength of movement. Sometimes ultrasound compares the tendency of sound waves to bounce off of versus to pass through a structure. Bone density, for example, is sometimes measured in this way.

Preparing for the test: Preparation is often unnecessary. When the test involves looking at structures or growths within the abdomen, the person is told to refrain from eating or drinking for about 6 hours before the test. If the test involves the urinary tract or the lowest part of the abdomen (pelvis) the person is asked to drink a large amount of water about 1 to 2 hours before the test. Most medications are not affected by the test and need not be changed. However, the scheduling of certain drugs, for example, those used to treat diabetes, may need to be adjusted.

What to expect during the test: The person usually changes into a loose-fitting gown. Then, depending on the area of the body being tested, the person may be asked to sit or lie down on a stretcher or examination table. Most people find an ultrasound in which the transducer is on the outside of the body to be simple and painless. They may experience slight pressure as the examiner moves the transducer about and presses downward occasionally to adjust the images that are being produced. Some people experience discomfort if they must lie down for the ultrasound, especially people who find it difficult to lie flat.

If the ultrasound involves passing a transducer inside the body, additional steps are taken, as in esophagogastroduodenoscopy and prostatic biopsy. The person may experience some discomfort.

What to expect after the test: Most often, usual activities can be resumed immediately after the test.

Potential problems: Ultrasound on the outside of the body is very safe. Rarely, when ultrasound involves passing the transducer inside the body, for example, the rectum, vagina, or esophagus, an injury occurs. Bleeding and infection may occur with such an injury.

Coronary Angiography

Other names: Coronary arteriography, cardiac catheterization, cardiac cath, heart cath.

Related tests: Angiography is done to evaluate arteries in many areas of the body. Kidney or renal angiography is done to look for blockages of arteries that supply the kidneys. Cerebral angiography is done to look for blockages of the arteries that supply the brain or to evaluate blood flow to tumors. Peripheral or extremity angiography is most often done to look for blockages of arteries that supply the legs.

Why the test is done: Coronary angiography is done to look for blockages in the arteries that supply the heart with blood (coronary arteries). Most often, the test is performed in people with symptoms. It may be done in people who have already had a heart attack to assess blood flow to the undamaged parts of the heart. If the test is done for reasons other than evaluating arteries, the term catheterization may be used. For example, it may be done to look for abnormal bulges in the wall of the heart (aneurysms) or damaged heart valves. Tissue samples may be obtained if infection or inflammation is suspected. The test may also be used to assess how well a transplanted heart is functioning.

How the test is done: A catheter is inserted into a blood vessel, usually an artery in the leg or arm. The catheter is threaded through larger and larger arteries until it reaches the aorta (the largest artery, which carries blood from the heart) and the heart. Dye is injected through the catheter, usually several times during the course of the test, to highlight the coronary arteries and the chambers of the heart. In some cases, the tip of the catheter has a camera that can transmit pictures of the inside of the arteries and heart to a video monitor. If tissue samples are needed, an instrument can be inserted through the catheter to obtain samples.

Preparing for the test: Because driving is not allowed until the day after the test, the person is told to arrange for a ride home. The person is also told to refrain from eating or drinking for 12 hours before the test. Adjustments to the scheduling and dosages of medications may be needed.

What to expect during the test: The person changes into a loose-fitting gown. The person lies on a table and is asked to remain as still as possible throughout the test. If the catheter is to be inserted into a blood vessel in the groin, hair is shaved from the area. A numbing drug (anesthetic) is injected at the site where the catheter is to be inserted. A small cut is made so that the catheter can be inserted safely into the vessel. After the catheter is inserted, a sedative may be given, which results in drowsiness but not sleep. The test itself usually requires about 1 hour.

Coronary angiography may be uncomfortable for some people, especially for those who find it difficult to lie still for a prolonged period. Each time dye is injected through the catheter, a brief sensation of warmth and a metallic taste may be experienced.

What to expect after the test: Pressure is usually applied after the catheter is removed. A bandage is placed over the incision site. Pressure is then continued, often by placing a small bag filled with sand on the bandage. The person is monitored in a recovery area for several hours, with blood pressure, heart rate, and breathing rate measured regularly. After about 4 hours, the person is allowed to sit and then stand and walk a bit. Usually the person is able to return home after about 6 hours but is advised to rest at home for the remainder of the day. The person is asked to call if bleeding or swelling occurs at the site where the catheter was inserted.

Potential problems: Uncommonly, a person has an allergic reaction to the dye. A blood clot may develop in the vessel where the catheter was inserted (thrombus), or bleeding (hematoma) may develop at the insertion site. Occasionally, the blood vessel may be damaged where the catheter was inserted, and a bulge (aneurysm) can develop. Rarely, other complications can occur, such as a heart attack, abnormal heart rhythm, stroke, or even death.

Colonoscopy

Other names: Lower endoscopy.

Why the test is done: Often, a colonoscopy is done to screen the lower digestive tract for evidence of cancer in people who have no symptoms. Also, it may be performed to look for noncancerous (benign) tumors or cancer in people who have been found previously to have noncancerous tumors. Colonoscopy may be used to look for recurring cancer in people who have had colorectal cancer. The test is also done to identify the source of bleeding from the digestive tract. Less often, the test is performed to look for a cause of persistent diarrhea or constipation.

Colonoscopy sometimes has a role in treatment, because it allows a doctor to remove polyps (noncancerous growths that can become cancerous), stop bleeding, or open up the large intestine or rectum in people who have a narrowing or partial blockage.

How the test is done: A type of flexible endoscope called a colonoscope is inserted through the anus and then passed along the length of the large intestine. A doctor can view the inside of the large intestine by looking through the colonoscope or at a television monitor.

Preparing for the test: Many medications are not affected by the test. However, the scheduling and dosage of some medications may need to be adjusted on the day before and the day of the test.

The person is told to refrain from taking aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) during the week before the test. These drugs increase the risk of bleeding. Almost always, warfarin, an anticoagulant (a drug that prevents clots), must be temporarily stopped before the test. Often, when warfarin is stopped, another anticoagulant is given by injection or intravenously until just before the test and briefly afterwards, until warfarin can be safely restarted. People with artificial heart valves or certain types of prostheses are given antibiotics before and just after colonoscopy to prevent infection.

The person is told to refrain from eating and to drink only clear liquids on the day before the test. To clean out the intestine of all stool, the person consumes a special laxative. The laxative is mixed with or taken with a large amount of water.

Because driving is unsafe for several hours after the test, the person is told to arrange for a ride home.

What to expect during the test: The person changes into a loose-fitting open-backed gown and lies on a stretcher or examination table. An intravenous line is inserted so that a sedative can be given. The sedative causes the person to become very drowsy or to fall asleep. If the person wishes to remain alert enough to watch the television monitor along with the doctor, a smaller dose of sedative may be given. A small device is clipped onto the person's finger so that the level of oxygen in the blood can be monitored. The person is then positioned on his side with one knee bent, and the colonoscope is inserted. Air is sometimes blown into the large intestine to widen (dilate) it and water is sometimes used to flush out any remaining stool.

The test is usually completed in as little as 30 minutes. It may take up to 90 minutes, especially if the large intestine has not been completely emptied or if polyps are removed or other tissue samples are taken. Colonoscopy may rarely be uncomfortable for some older people, especially for those who find it difficult to lie still for a prolonged period.

What to expect after the test: The person remains in a recovery area for about 1 to 2 hours while blood pressure, heart rate, and breathing rate are monitored. The person is then instructed to rest or to greatly reduce usual activities for the remainder of the day. Large amounts of gas may be passed for many hours, and normal bowel function may take a few days to return. The person is told to refrain from taking aspirin and other NSAIDs for several days after the test.

Potential problems: Older people may find taking the laxative before the test to be a bit stressful. They can become dehydrated from the laxative and from the restrictions on drinking and eating that are necessary for test preparation.

Rarely, a heart valve or a prosthesis becomes infected. In rare cases, the large intestine or rectum is torn or the wall is penetrated (perforated) by the colonoscope. Older people, especially those who have multiple bulges (diverticula) in the wall of the large intestine, are more likely to have their intestine perforated than are younger people. Perforation usually results in bleeding and infection and often requires surgery.

Esophagogastroduodenoscopy (EGD)

Other names: Upper gastrointestinal endoscopy.

Why the test is done: An EGD is done to check the inside lining of the esophagus, stomach, and upper part of the small intestine (duodenum) for problems such as inflammation, ulcers, tears, blockages, and noncancerous (benign) or cancerous (malignant) tumors. Usually the test is done when a person has difficulty swallowing, persistent nausea and vomiting, vomiting of blood, or pain that is not relieved by drugs.

How the test is done: An endoscope is inserted through the mouth and throat and passed into the esophagus, stomach, and duodenum. The doctor can view the inside of these organs by looking through the endoscope or at a television monitor.

Preparing for the test: Most often, medications are not affected by the test and need not be changed. However, the scheduling and dosage of some medications may need to be adjusted.

The person is told to refrain from taking any aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs) during the week before the test. These drugs increase the risk of bleeding during the test. Almost always, warfarin, an anticoagulant (a drug that prevents clots), must also be temporarily discontinued a week before the test. Often, when warfarin is discontinued, another anticoagulant is given by injection or intravenously until just before the test and briefly afterwards, until warfarin can be safely restarted. People with artificial heart valves or certain types of prostheses are given antibiotics prior to and just after EGD to prevent infection.

Because driving is unsafe for several hours after the test, the person is told to arrange for a ride home. Eating and drinking are prohibited for 8 hours before the test.

What to expect during the test: The person removes all clothing above the waist and changes into a loose-fitting open-backed gown. The person lies partly reclined on a stretcher or examination table. The back of the throat is sprayed with a numbing drug (topical anesthetic) to prevent gagging. A mouthpiece is inserted to prevent biting on the endoscope. An intravenous line is inserted so that a sedative can be given.

As the endoscope is inserted, the person is asked to swallow so that the endoscope can be passed easily into the esophagus. The sedative may then be increased slightly if the person prefers to sleep through the procedure. Tissue samples are sometimes taken for a biopsy. EGD is sometimes completed in as little as 10 minutes but often lasts 20 to 30 minutes, especially if tissue samples are taken. The test may be uncomfortable, especially for people who find it difficult to lie still for a prolonged period.

What to expect after the test: The person remains in a recovery area for about 1 to 2 hours while blood pressure, heart rate, and breathing rate are monitored. Afterward, the person is instructed to rest or to greatly reduce usual activities for the remainder of the day. The person is told to refrain from eating or drinking for a few more hours. Gas may be passed for many hours. The person is told that aspirin or other NSAIDs should not be taken for several days after the test.

Potential problems: Rarely, the esophagus, stomach, or duodenum is injured by the endoscope. Such an injury, which is a bit more likely for older people than for younger people, may result in bleeding and infection. The risk of aspiration, in which gastric juices travel up the esophagus and down into the lungs, is higher for older people as well. Aspiration may result in a fever and pneumonia. Rarely, an artificial heart valve or prosthesis becomes infected.

Polysomnography

Other names: Sleep study.

Why the test is done: Polysomnography is done to diagnose disorders that can cause insomnia or excessive daytime sleepiness. Such disorders include sleep apnea; rapid-eye-movement (REM) sleep behavior disorders; limb movement disorders, such as restless legs syndrome; and narcolepsy.

How the test is done: Polysomnography is performed in a sleep laboratory, almost always within a hospital. Sensors are attached to the person, allowing for various body functions to be continuously recorded during sleep, and the person is videotaped. The body functions recorded may include electrical activity of the brain; oxygen levels in the blood; the rate of air flow in and out of the lungs; heart rate; blood pressure; and movement of muscles in the eyes, jaw, and legs. The results are analyzed to determine how long it takes a person to fall asleep, how long the person sleeps, and how frequently the person awakens. Information is also available on the time spent in different stages of sleep and whether the person has periods during which breathing stops briefly (apnea) or becomes very shallow (hypopnea).

Preparing for the test: The person is told to maintain regular sleep habits up to and including the night before the test. The person is asked to bring comfortable clothing suitable for sleep. Most medications are not affected by the test and need not be changed. However, the person is told to avoid taking any drugs that affect sleep, such as sleep aids, stimulants, and alcohol.

What to expect during the test: Sensors are attached to the scalp, face, chest, and legs. After the sensors are attached, the person has several minutes to relax and become accustomed to wearing all the sensors and wires.

The test usually involves recordings of body functions for an entire night of sleep (a full study). Alternatively, the test may involve recordings for about half a night of sleep followed by a period when recordings are performed while various treatments are tried (a split study). The second half of the study is performed to measure the response to treatment if a problem is identified during the first half of the night. Occasionally, the test is continued the following day to measure naps and daytime sleepiness (multiple sleep latency test).

Many people worry at first that they will be unable to sleep while attached to the sensors and wires. However, once the study gets underway, most people are able to get comfortable and fall asleep.

What to expect after the test: Usual activities can be resumed immediately after the test.

Potential problems: Polysomnography is safe. Problems are very infrequent.

Electromyography (EMG) and Nerve Conduction Velocity (NCV)

Other names: None.

Why the test is done: EMG and NCV testing provide information about how well the muscles and nerves are functioning. The pattern of any abnormalities detected often suggests possible causes, such as pressure on or entrapment of a nerve. Results can also help distinguish between and diagnose diseases of muscles and diseases of nerves.

How the test is done: When muscles contract, measurable electrical signals are generated. Electrical signals traveling along nerves can also be recorded. An EMG requires that very thin needles (similar to pins) be inserted through the skin so that they are situated in or very near muscles at specific points of the arms or legs. The needles are electrodes that transmit the electrical activity of the muscles to a monitoring device. An NCV test requires that a nerve stimulator be placed on the skin, together with a recording electrode located further along the nerve. Information on the velocity and the strength of the electrical activity is sent to a monitoring device.

Preparing for the test: Most medications are not affected by the test and need not be changed. However, the person may be told to refrain from taking any aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs) during the week before the test, because these drugs can increase the risk of bleeding during the test. Similarly, the scheduling and dosage of warfarin (a drug that prevents clots) may need to be adjusted. On the day of the test, the person is asked to refrain from using hand cream or lotion that might interfere with adherence of electrodes to the skin and to wear comfortable, loose-fitting clothes.

What to expect during the test: Depending on the area being tested, the person may be asked to change into a gown. The person then sits or lies on a table. Sometimes only one test is done, but often EMG and NCV tests are done together. Both can usually be done in about 30 to 60 minutes.

For an EMG, skin in the area where each needle is to be placed is cleaned with alcohol. A brief but painful prick is felt as each needle is inserted. Usually only a few needles are used. For an NCV, the placement of electrodes is on the surface of the skin.

What to expect after the test: Aching in the areas that were tested may persist for several hours. Most often, usual activities can be resumed immediately after the test.

Potential problems: Very rarely, a person develops an infection or bleeding at the site where a needle was inserted.

Prostatic Biopsy

Other names: Biopsy of the prostate.

Why the test is done: A prostatic biopsy is done to examine the prostate gland for evidence of cancer. The test is performed in men suspected of having cancer on the basis of the physical examination, blood tests, and ultrasound scanning.

How the test is done: A doctor inserts into the rectum a device that combines an ultrasound probe with a thin, hollow needle guide. Once the device is positioned appropriately, a thin needle is repeatedly passed through the guide, penetrating through the wall of the rectum and into the prostate, until several tissue samples have been obtained. The tissue is then examined under a microscope in a laboratory.

Preparing for the test: Most medications are not affected by the test. However, the person is told to refrain from taking aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs) during the week before the test. These drugs increase the risk of bleeding during the test. Warfarin, an anticoagulant (a drug that prevents clots), must also be temporarily discontinued during the week before the test. Often, when warfarin is discontinued, another anticoagulant is given by injection or intravenously until just before the test and briefly afterwards, until warfarin can be safely restarted. An antibiotic is taken, usually the day before, the day of, and the day after the test. The man is usually told to take an enema the morning of the test and to eat a light breakfast.

What to expect during the test: The man changes into a loose-fitting open-backed gown. He then lies on a table and must remain as still as possible. A numbing drug (anesthetic) and a sedative are given. The man feels pressure when the doctor inserts the ultrasound probe--needle guide combination into the rectum. This may be followed by a pricking sensation as the needle is passed through the needle guide repeatedly to obtain several tissue samples. The test takes about 20 to 30 minutes.

What to expect after the test: Usual activities can be resumed immediately. However, for a few days after the test, the rectum may feel sore, and a small amount of blood may be visible in urine or in ejaculate. The man is asked to call his doctor if blood remains visible for more than a few days or if he experiences a fever or bleeding from the rectum.

Potential problems: There is a small risk that the needle used to obtain tissue samples will cause bleeding. Infections, although uncommon, may occur.

Skin Biopsy

Other names: Biopsy of the skin.

Why the test is done: A skin biopsy is done to examine skin growths or other abnormal areas of skin tissue for evidence of cancer or inflammation.

How the test is done: A doctor performing a skin biopsy can choose from several options. With a growth that is raised above the level of the surrounding skin, a shave biopsy can be performed. In a shave biopsy, a sharp blade (scalpel) is used to shave off the growth. If the growth extends deeper into the skin, a scalpel is used to perform an excisional biopsy. In an excisional biopsy, some or all of the growth is removed. In some cases, especially when inflammation is suspected, a punch biopsy is performed. In a punch biopsy, a sharp circular punch is used to push through the skin. When the hollow punch is pulled back, it contains a core of tissue from the full thickness of the skin. The biopsy is examined under a microscope in a laboratory.

Preparing for the test: Often, preparation is not needed. However, if the doctor expects to obtain tissue from deeper layers of the skin, the person may be asked to refrain from taking aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) the week before the test. These drugs can increase the risk of bleeding. Warfarin, an anticoagulant (a drug that prevents clots), may also be temporarily discontinued a week before the test. Often, when warfarin is discontinued, another anticoagulant is given by injection or intravenously until just before the test and briefly afterwards, until warfarin can be safely restarted.

What to expect during the test: The person can remain dressed if the test involves an easily accessible area, such as the lower arm. Otherwise, the person changes into a loose-fitting open-backed gown. The person may sit or lie on a table and must remain as still as possible. The skin surrounding the area where the tissue is to be removed is cleaned and injected with a numbing drug (anesthetic). The person may feel pressure from the scalpel or punch used to remove the tissue. The test usually takes about 5 to 15 minutes. A solution that stops bleeding may be applied, or one or a few stitches (sutures) may be used to close the small wound.

What to expect after the test: Usual activities can often be resumed immediately if the wound is very small. However, if stitches are needed, the person may be advised to keep the area of the wound dry and to avoid heavy lifting or vigorous exercise until the stitches are removed.

Some steps must be followed to care for the wound. If stitches are not needed, the site is covered with a dressing or bandage. The person is given directions to care for the wound until it heals in a few days or several weeks, depending on the type of biopsy. Directions usually involve changing the dressing at least once a day after cleansing the site and applying antibiotic ointment. The person may be advised to check the site each day and to report any bleeding or increasing redness or pain.

Potential problems: A scar may form. The size of the scar depends on the type of biopsy performed. Rarely, the site becomes infected or bleeds excessively.