Diagnostic tests


Diagnostic tests are used in healthcare settings to help determine the cause of a patient's symptoms and medical complaints. The cause of a patient's symptoms and medical complaints is known as a diagnosis. Once a diagnosis is given, the doctor can decide which type of treatment will be most helpful. When a diagnostic test indicates that a medical condition is present in the patient, the diagnosis is called a positive diagnosis. When a diagnostic test indicates that a medical condition is not present, the diagnosis is called a negative diagnosis. Diagnostic tests are rarely completely accurate. However, they may help the doctor understand what is going on in the body. Sometimes tests return incorrect results. These incorrect results are classified as either a false positive or a false negative. A false negative is a diagnosis that incorrectly says a patient does not have a condition or disease when in fact the condition or disease is present in the patient's body. A false positive is a diagnosis that incorrectly says a patient does have a condition or disease when in fact the condition or disease is not present in the patient's body. If the doctor believes that the test results may be a false negative or false positive, then the test may be done again.
Most diagnostic tests involve a small amount of risk of causing problems in the patient's body. However, in most cases the chance of determining what is wrong with the patient is greater than the risk of injury. Before undergoing any diagnostic test, the patient and their loved ones should feel free to ask questions about the possible risks, benefits, and outcomes of the test before signing an informed consent form. The informed consent form is a paper in which the patient signs their name to show that they understand all of the risks and benefits of a diagnostic test. Patients should not sign this form until they feel that they completely understand what will happen in the test and what the risk of damage to the body may be.
The diagnostic tests used today rely heavily on specialized technology. Regardless, the patient may feel uncomfortable during the process of a diagnostic test. Knowing why the test is being performed and what to expect before the test begins may help to decrease feelings of anxiousness.
In addition to being used as a tool for making a diagnosis, diagnostic tests may also be used to measure how much a treatment is helping a patient recover from a disease or to confirm that the patient is still free of disease. Tests may also be done to estimate how likely a patient is to recover from a disease; the word for this concept is "prognosis."
There is no one diagnostic test that will figure out everything that might be happening in the patient's body. For this reason, patients with complicated symptoms may need to go through many diagnostic tests. Some tests are very general and check body functions or organs; these tests may tell a doctor if a cluster of possible diagnoses are affecting the patient. For instance, endoscopies are done to give the doctor a general idea of what is going on in the patient's body, but other tests are conducted after this one to figure out the specific cause. Other tests, such as blood tests, look for problems that may involve many body systems or functions.
Medical tests may help to explain the cause of symptoms, or how much a treatment is contributing to a patient's prognosis. Normal test results may help reassure patients that they do not have a serious illness.


Diagnosis, diagnostic care, disease, methods of diagnostic care.

cardiovascular (heart, circulation, and blood vessels) tests

Cardiac catheterization: A cardiac catheter or angiogram is a procedure that identifies possible problems with the heart or its arteries. During a catheterization, a thin plastic tube, called a catheter, is inserted into a blood vessel in the patient's groin or arm. The catheter is guided up toward the heart. A special dye is injected into the catheter so X-rays can show if the patient has any artery blockages or other heart problems. Cardiac catheterization is also called coronary angiography.
Echocardiogram: An echocardiogram is a special imaging machine with a microphone-like attachment in order to create a recorded movie of the heart in order to view the heart's four chambers, valves, and its movements. This movie is made using the electrical signals produced by the heart that fuel the pumping of blood throughout the body. Results are analyzed by doctors to determine if any heart problems are present. Examples of these problems include the heart's overall motion and the condition of the valves that keep blood flowing in only one direction. Small pads are stuck onto the chest around the heart. Wires are attached to the pads and these connect to a machine that takes an electrical recording of the heart beat.
Electrocardiogram: An electrocardiogram (ECG or EKG) is a graphic record of the electrical activity of the heart as it contracts and rests. About ten electrodes are attached to the skin of the legs, arms, and chest, and information about the body is recorded on specialized machines. It can be used in the diagnosis of a number of heart conditions, including valve disorders, arrhythmias, and heart attack. The heart functions by electrical currents, which are carried through this organ using special types of cells. When the heart does not receive these signals or when the electrical current malfunctions, the organ may not deliver blood to the rest of the body at the right times.
Electrophysiological (EP) testing of the heart: In this test, electrodes are attached to the heart muscle. This test is more specific than the ECG and is usually performed to tell doctors why the heart is not beating as it should. When part or all of the heart's four chambers do not beat normally, a patient has a condition known as arrhythmia.
Exercise stress test: The exercise stress (treadmill) test enables doctors to record the heart's electrical activity that may not occur at rest. The heart will need to pump more blood and oxygen to the body and the heart muscle as the individual exercises. The test can show if the blood supply is reduced in the arteries that supply the heart. It also helps doctors know the kind and level of exercise appropriate for a patient. The stress test is performed in an exercise laboratory (in a hospital or clinic) where the heart rate and blood pressure are recorded at rest. Sticky electrodes are attached to the chest, shoulders, and hips and are then connected to the electrocardiogram (ECG or EKG) portion of the stress test machine. The treadmill is then started at a relatively slow warm-up speed, then the slope and speed are increased to simulate exercise stress. The doctor monitors the heart rate, blood pressure, changes in the ECG pattern, irregular heart rhythm, and the individual's appearance and symptoms. Ideally, the test ends and then the treadmill is stopped when the patient achieves a target heart rate (85% of the maximal heart rate predicted for the patient's age). However, if the patient is doing extremely well at peak exercise, the treadmill test may be continued further. The test may be stopped prior to achievement of the target heart rate if the patient develops significant chest discomfort, shortness of breath, dizziness, or unsteady gait or if the ECG shows alarming changes or serious irregular heartbeats. It may also be stopped if the blood pressure (BP) rises or falls beyond acceptable limits. Please note that the systolic BP (upper number) may normally rise to 200 at peak exercise. At the same time, the diastolic BP (lower number) remains unchanged or falls to a slight degree. In contrast, the BP of patients with hypertension or high BP will show a rise of both systolic and diastolic readings. The latter may rise above 90-100. In preparing for an exercise stress test, healthcare professionals recommend not to eat or drink for three hours prior to the procedure. This reduces the likelihood of nausea that may accompany strenuous exercise after a heavy meal. Diabetics, particularly those who use insulin, will need special instructions from their physician. Also, it is recommended to wear comfortable clothing and shoes that are suitable for exercise. The stress portion of the test is similar to what a person would expect from any strenuous form of exercise (jogging or running up a flight of stairs). As noted earlier, experienced healthcare professionals are in attendance to manage any rare complications such as sustained irregular heart beats, unrelieved chest pain, or even a heart attack. For people who may be unable to perform the actual stress tests, a doctor may give the patient a drug that makes the heart beat faster in order to determine heart health while putting the organ under less stress than exercise on a treadmill.
Holter monitor: Holter monitoring detects irregular heart rhythms. Patients wear a small recording box attached to their chest by five adhesive electrode patches for 24-48 hours. Doctors analyze the results to determine if arrhythmia is present.
Ultrasound of the legs (venous ultrasound): An ultrasound is a procedure in which high-energy sound waves (ultrasound) are bounced off internal tissues or organs and make echoes. The echo patterns are shown on the screen of an ultrasound machine, forming a picture of body tissues called a sonogram (also called ultrasonography). Ultrasound is painless, and can rapidly detect abnormalities often right in the doctor's office. A venous ultrasound indicates if there is a blockage in a leg vein (a blood clot).

dermatologic (hair, skin, nails) tests

Skin biopsy: During this procedure, a healthcare provider will inject an anesthetic into the skin, which numbs the area. Then a small sample of skin is removed and analyzed under a microscope to determine whether the patient has a skin disorder, such as skin cancer.

endocrine (hormonal) tests

Thyroid profile: In a thyroid profile, a blood sample is taken to measure the levels of certain chemicals that are released into the body by the thyroid. This test is relatively painless and is done to measure if the thyroid is functioning correctly or if medications are helping the thyroid function.

gastrointestinal (digestive and liver) tests

Abdominal CT (computed tomography) scan: A CT scan uses x-rays to take many pictures of the body that are then combined by a computer to give a detailed picture. A CT scan can often show whether a cancer has spread to the liver, lungs, or other organs. CT scans can also be used to help guide a biopsy needle into a tumor. A new way to use a CT scan is to do a "virtual colonoscopy." After stool is cleaned from the colon, and the colon is filled with air, a computer can put together a picture of the inside of the colon. This method requires the same preparation as for a colonoscopy, and there is some discomfort from the bowel being filled with air. If anything abnormal is seen, such as polyps, then a follow-up colonoscopy will be needed.
Abdominal ultrasound: Ultrasound uses sound waves to produce a picture of the inside of the body. Two special types of ultrasound may be useful for people with colon or rectal cancer. In one, the instrument that gives off sound waves is placed into the rectum. In the other test, the instrument is used during surgery and is placed against the surface of the skin over the liver to see if cancer has spread there.
Anoscopy: The anoscopy views the anal canal, as well as possibly parts of the rectum and colon. It is commonly used to detect fistulas, hemorrhoids and fissures. This is different than a flexible sigmoidoscopy which views the rectum and sigmoid colon.
Barium enema: A barium enema, also called a lower GI or gastrointestinal series, is an x-ray study in which liquid barium is inserted into the rectum and colon through the anus. Thorough cleaning of the large intestine is necessary for accurate pictures. Test preparations include following a clear liquid diet, drinking a bottle of magnesium citrate (a laxative), and using warm water enemas to clear out any stool particles. The doctor may also instruct other preparations for this procedure as well. This test may be done in a hospital or clinic 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 his or her side while a well lubricated enema tube is inserted into the rectum. As the enema enters the body, the patient might have the sensation that their stomach is being filled. The barium, a type of chemical that shows up on an 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 healthcare provider on an X-ray fluoroscope screen. Air may be filled into the colon to stretch the tissue and provide better images (often called a "double-contrast" exam). If air is used, then the enema tube will be reinserted and a small amount of air will be introduced into the colon and more X-ray pictures are taken.
Barium swallow (or upper gastrointestinal series or "upper GI series"): The upper GI series is a series of X-rays of the esophagus. The X-ray pictures are taken after the person drinks a solution that contains barium. The barium coats and outlines the esophagus on the X-ray. This procedure is also called an esophagram.
Colonoscopy: This procedure is the most reliable sensitive test for colon cancer, rectal cancer, and polyps. In a colonoscopy, the instrument used is called a colonoscope, a long, flexible, and slender tube attached to a video camera and monitor. This allows the doctor to view the entire colon and rectum. If any polyps are found during the exam, then the doctor may remove them immediately or take tissue samples (biopsies) for analysis. This is done through the colonoscope and is virtually painless, but the patient may receive a mild sedative for comfort. Preparation for the procedure involves drinking a large amount of fluid containing a laxative to clean out the colon.
Fecal occult blood (FOB) test: This test checks a sample of the stool for blood. It can be performed in the doctor's office, or a kit may be given to the patient that explains how to take the sample at home. In colorectal cancer, most polyps don't bleed, which can result in a negative stool test result, even though an individual may have cancer. Blood may also be the result of hemorrhoids or minor tears, so it can only aide in the diagnosis of colorectal cancer.
Flexible sigmoidoscopy: The doctor uses a flexible slender and lit tube to examine the rectum and sigmoid portion of the colon (approximately the last two feet of the colon). The test is fast but can sometimes be uncomfortable. If a polyp or colon cancer is found during this exam, then the doctor will recommend a colonoscopy to look at the entire colon and remove any polyps for further examination under a microscope.
Heidelberg capsule test: This test is used to determine if the patient's digestive tract is producing enough gastric acid. The patient swallows a pill, which contains miniature electronic monitoring equipment. The capsule measures the pH of the stomach, small intestine, and large intestine. The pH of these parts of the digestive tract are transmitted as a signal to an antennae worn by the patient.
Liver biopsy: A biopsy is a procedure involving the removal of a sample of tissue for microscopic analysis. Biopsies can be accomplished with a biopsy needle (passed through the skin into the liver or tumor in question) or by open surgical incision. A liver biopsy is often used to determine the cause of hepatitis or to detect liver cancer.
Percutaneous transhepatic cholangiography (PTCA): Percutaneous transhepatic cholangiography is an x-ray procedure that can help to detect blockages in the liver or bile ducts. With guidance from the fluoroscope (an x-ray machine that projects images onto a TV screen), the bile duct is located, and the contrast medium injected. The contrast medium then flows through the ducts and can be seen on the fluoroscopic monitor. The patient is usually not awake for this procedure. Some sort of sedative is always given.
Stomach acid testing: Also known as a gastric acid test, this procedure uses a tube to suck out some of the digestive fluids that are present in an empty stomach. A flexible tube is passed through the nose or throat, and the tube removes the fluids. The amount and contents of these fluids are then analyzed. The results of this procedure may help in finding the cause of ulcers, diagnosing food malabsorption, or to evaluate the secretion of gastrin.
Upper endoscopy (or esophagogastroduodenoscopy or "EGD"): An upper endoscopy is a medical test in which a doctor places an endoscope (a thin, flexible instrument that has a light and lens or camera) down the patient's throat to view the inner lining of the esophagus, stomach, and duodenum.

urinary (kidneys) tests

Cystourethrogram: A Cystourethrogram is a specific x-ray that examines the urinary tract. A catheter (hollow tube) is placed in the urethra (tube that drains urine from the bladder to the outside of the body), and the bladder is filled with a liquid dye. X-ray images will be taken as the bladder fills and empties. The images will show if there is any reverse flow of urine into the ureters and kidneys, called retrograde flow.
Cystoscopy: In this procedure, local anesthesia is administered and a cystoscope is inserted into the bladder through the urethra to allow the doctor to detect abnormalities. A cystoscope is a thin telescope-like tube with a tiny camera attached.
Intravenous pyelogram (IVP): In this procedure, a contrast agent (called a radiopaque dye) is administered through a vein (intravenously or IV), and x-rays are taken as the dye moves through the urinary tract. IVP provides information about the structure and function of the kidneys, ureters, and bladder.
Kidney biopsy: In a kidney biopsy, tissue samples are taken to examine for cancer cells or other disorders.
Radionuclide scan of the kidneys: A radionuclide scan can help the doctor determine the type of kidney problem a patient is experiencing. The patient will receive a small dose of a radioactive substance either orally in liquid form or through an injection. Any abnormal areas will then appear on the films from the scan.
Urinalysis: A urinalysis is a group of physical and chemical tests done on a sample of urine to check for various disorders, including those of the kidneys and urinary tract. The test examines chemicals in the urine or may look for blood in the urine.

hematologic (blood and hormonal) tests

Blood tests: This is a very general test where blood is drawn from the patient for further analysis. The finger may be pricked or blood may be taken from a vein. This is one of the most common medical tests.
Carotid ultrasound (carotid doppler): The carotid doppler exam uses sound frequency in a range that is higher than human beings are able to hear to produce images of the carotid arteries in the neck on a viewing screen. The blood flow through these arteries is evaluated with doppler and color doppler. Color doppler involves the use of standard ultrasound methods to produce a picture of a blood vessel. In addition, a computer converts the doppler sounds into colors (typically red and blue) that are overlaid on the image of the blood vessel. These colors represent the speed and direction of the blood flow through the vessel. Carotid doppler studies are used to detect blocked or reduced blood flow in the arteries of the neck that could cause stroke. This test is also used to evaluate symptoms of dizziness, vision changes, and the loss of balance that may be caused by impeded or restricted blood flow through these blood vessels.
Lymph node biopsy: A lymph node biopsy can be performed to determine whether cancer cells are present. During the procedure, all or part of a lymph node is removed. A pathologist views the tissue under a microscope to confirm the diagnosis.

musculoskeletal (muscles, bones, and joints) tests

Bone density test for osteoporosis: This test measures bone density at various sites in the body. It can detect osteoporosis before a fracture occurs, predict the chances of fractures, and determine the rate of bone loss. This test can also monitor the effects of treatment if the test is conducted at intervals of a year or more. In this test, a painless X-ray is taken of the patient's bones.
Bone marrow biopsy: The bone marrow is sampled by a technique known as bone marrow aspiration. During this procedure, a thin hollow needle with a syringe attachment is used to aspirate (suction up) a teaspoon-sized sample of liquid bone marrow from the back of the hipbone. A larger needle is then employed to obtain a bone marrow biopsy ("core" biopsy), which removes roughly a one-sixteenth inch piece of bone marrow from the hip site. The individual is generally awake during the procedure, but local anesthetics (such as lidocaine) and sedatives (such as midazolam or Versed®) may be given. There is usually little to no pain involved. This test may determine cancer, the amount of white blood cells in the body, and other abnormalities in the marrow.
Bone scan: A bone scan is a technique that creates images of bone on a computer screen or on film. A small amount of radioactive material is injected into a blood vessel, which travels through the bloodstream and then collects in the bones and is detected by a scanner.
Computed tomography (CT): Computed tomography is a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general x-rays. Except for the injection of a dye (needed in some but not all cases), this is a painless procedure that can be done in an outpatient clinic.
Myelography: In this procedure, contrast material is injected into the thecal sac (the fluid surrounding the spinal cord and nerve roots within the spinal canal). X-rays of the spine are taken with the patient in various positions. This allows nerve tissue to be viewed with an x-ray and enables a doctor to trace any nerve entrapment. This is an invasive procedure that many people report to be unpleasant. This test examines possible problems with the nerves and bones in the spine.
X-rays: X-rays allow a physician to view the bones in the body. An X-ray photograph resembles the negative of an ordinary photograph, with dense tissues such as bones showing up as white shapes.

neurologic/cns (brain and nervous system) tests

Electromyography and nerve conduction studies: This procedure records the electrical responses of skeletal muscles while at rest and during voluntary action. At times, a special medical instrument may put off a small electrical stimulation in order to determine the way that the muscle responds. During this test, a small needle is inserted into a muscle to record the level of activity.
Magnetic resonance imaging (MRI) of the spine: An MRI is a computer imaging technique using a strong magnetic field and radio frequencies. This procedure creates a three dimensional picture of the body, which the doctor may examine to see if the tissues are healthy.
Spinal tap (or lumbar puncture): A lumbar puncture or spinal tap is a procedure in which a thin needle is inserted through the lumbar (lower) backbone, below the level of the spinal cord. Cerebrospinal fluid (CSF) is withdrawn through the needle and is then analyzed for the presence of lymphoma cells. This test is performed to see whether lymphoma has spread to the central nervous system. The procedure may be painful and requires the use of topical anesthetics such as lidocaine.

ocular/otic (eyes, ears, nose, and throat) tests

Fluorescein angiography (for diabetic retinopathy): This technique is used for visualizing and recording the location and size of blood vessels and any eye problems affecting them. Fluorescein dye is injected into an arm vein and then rapid sequential photographs are taken of the eye as the dye circulates.
Rapid strep test: For this test, a doctor uses a long cotton swab to take some material from the back of the throat. The results of this test can be ready in about 15 minutes. If something else is causing a sore throat, then these tests do not indicate what it is. Other tests are available that give more accurate results.
Scratch test for allergies: A scratch test is a skin test is used to determine whether a patient is allergic to certain substances, such as mold, dust mites, or animal dander. Patients who experience common allergy symptoms, such as sneezing, hives, watery eyes, runny nose, and itching are often tested to determine specific allergies. During the test, the skin is exposed to different allergens and then observed for an allergic reaction. Qualified healthcare providers can use the test to determine whether allergy-like symptoms are immune-mediated, and they can identify the specific substance(s) that trigger the reaction. Skin testing is often used to diagnose allergic conditions, including allergic asthma, dermatitis (eczema), and hay fever.
Snellen test for visual acuity: A Snellen test uses a chart with different sizes of letters or forms to evaluate visual acuity (sharpness of vision). The test shows how accurately a patient can see from a distance.
Tonometry: Tonometry is a procedure that measures the pressure inside of the eyes. The test is used to screen for glaucoma, a disease in which pressure inside the eyes increases to a degree that it impairs vision. In this test, a machine blows a small amount of air into the eye. The test may feel unusual, but it does not cause pain.

pulmonary/respiratory (lungs) tests

Bronchoscopy: During this test, a bronchoscope (thin flexible tube with a camera) is inserted into the trachea, through the mouth, and allows the healthcare provider to look inside the lungs and remove a small amount of lung tissue (biopsy) for analysis. If the patient has pulmonary eosinophilia, then the lung tissue will show elevated numbers of certain white blood cells.
Chest x-ray: An x-ray is an image produced by sending a beam of X-rays (very high energy electromagnetic radiation) through the body. Different tissues in the body have different densities and absorb and deflect X-rays differently. A camera records on photographic film the varying levels of X-rays that have passed through the body. A chest x-ray is performed when certain lung conditions, such as pneumonia, lung cancer, or emphysema are suspected.
Mediastinoscopy: Mediastinoscopy is a surgical procedure to examine the inside of the upper chest between and in front of the lungs (mediastinum). In this test, an instrument passes through a small incision at the base of the neck and a biopsy of lymph nodes is taken. This helps determine how far cancer has spread and whether surgery is a reasonable option for removing the tumor.
Oxygen saturation test: An estimate of your oxygen saturation can be made easily and painlessly with a pulse oximeter (a device that fits on your finger). This device shines a light through one side of your finger, and a detector measures the light that comes through the other side. This machine can make a good estimate about an individual's oxygen saturation because blood cells that are saturated with oxygen absorb and reflect light differently than those that are not. Blood cells are a bright red when they are loaded with oxygen, and they change to a bluish color when they are no longer carrying a full load of oxygen.
Pleural fluid sampling (or thoracentesis): This is a procedure to remove fluid from the space between the lining of the outside of the lungs (pleura) and the wall of the chest. An accumulation of excess fluid between the layers of the pleura is called a pleural effusion.
Pulmonary angiogram: A pulmonary angiogram is an invasive study in which a catheter is introduced into a vein and enters an artery of the lung. Contrast dye is injected and pictures of the lung vessels are taken. Clots within the pulmonary vessels indicate pulmonary embolism, a potentially life-threatening condition.
Pulmonary function testing: Pulmonary function testing is an examination measuring an individual's lung capacity, speed of exhalation, and oxygenation after a period of exertion. This type of test is useful in the diagnosis of chronic obstructive pulmonary disease (COPD), occupational lung disease, emphysema, and asthma.
Sputum evaluation (and sputum induction): If a doctor suspects a patient has pneumonia, then the doctor may examine some of the patient's sputum. Sputum is the phlegm that is coughed out of the lungs. This test is used to determine what type of bacteria or other infectious agent might be the cause of the pneumonia.
Tuberculosis (TB) skin test: The standard diagnostic tool for TB is a skin test called the mantoux test (tuberculin test). However, this test cannot determine if the infection is active or inactive. It also cannot tell the difference between a TB infection and a TB vaccination. Therefore, additional tests, such as a chest X-ray, a sputum culture, or both are usually performed to determine whether the patient has an active TB infection.
Ventilation-perfusion (or "V-Q" scan): A ventilation/perfusion scan, also called a V/Q scan, is a medical test to measure the circulation of air and blood within a patient's lungs. The ventilation part of the test evaluates the ability of air to reach all parts of the lungs while the perfusion part measures how well the blood circulates within the lungs. This test is most commonly done in order to check for the presence of a blood clot or abnormal blood flow inside the lungs (pulmonary embolism or PE), although computed tomography with radiocontrast is now more commonly used for this purpose.