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25 Medical Tests Your Doctor Should Tell You About ... And 15 You Can Do Yourself
By Deborah Mitchell
St. Martin's PressCopyright © 2010 Lynn Sonberg Book Associates
All rights reserved.
WHAT YOU NEED TO KNOW ABOUT MEDICAL TESTS
It's a common occurrence: you walk into your doctor's office with a complaint and you walk out with one or more orders for tests: blood work, X-rays, scans — you name it. Perhaps you are given a piece of paper with a list of instructions: don't eat or drink anything for a specific number of hours before the test, be sure to drink a specific formula before the test, don't wear jewelry or powder, and so on.
Or maybe you are admitted into a hospital where you are poked, prodded, and then wheeled to different areas of the facility for various tests. In either case, your mind is racing with questions: Why do I need this test? What will the results tell me about my condition? How is the test done? Is it going to be painful? How do I prepare for it? Are there any side effects or precautions I need to consider?
Okay, now let's assume that the results of your tests have come in, and they should be shared with you. When they are, you may find yourself puzzled or confused by the explanation offered by the doctor or other healthcare professional, and perhaps you are too embarrassed to ask questions or for clarification. You're not alone: many health-care consumers feel the same way.
But your health and that of your family is serious business, and you need and deserve to know about the tests you take and what they mean. That's why the goal of this book is to answer questions you and other health-care consumers have about some of the most common tests prescribed by health-care practitioners that are used to screen for or diagnose the more common diseases and conditions. In addition, we also introduce you to a rapidly growing segment of the health-care arena — self-testing, or home medical test kits. These are tests you can typically do at home, either by purchasing a test kit from your neighborhood pharmacy or from a company online. We have dedicated an entire chapter to this topic.
HOW DID WE CHOOSE THE TESTS IN THIS BOOK?
You may be wondering, of the hundreds of diagnostic and screening tests that are available, how and why did we choose the ones that are in this book? We used several criteria, including how often a test is ordered, the prevalence of the condition(s) for which it is used, the number of conditions it can diagnose or screen for, and its reliability. For example, the complete blood count (CBC) is one of the most ordered tests because it is often part of a routine checkup or screening, can be used as a follow-up procedure to monitor certain conditions or treatments, and is frequently part of an evaluation done to check on a patient's symptoms. A CBC is helpful in the diagnosis and screening of dozens of medical conditions, many of which are among the more common health problems people face, ranging from anemia to coronary heart disease to kidney infections.
Whether the test you need is done by a medical professional or by you at home, this book provides the most up-to-date information about these procedures so you can feel more confident when discussing them with your doctor or gathering health information for your own purposes. The information in this book can help you know which questions to ask your doctor, nurse, pharmacist, or other medical professional, and hopefully eliminate much of the mystery and any anxiety you may have about the tests.
In addition to explaining the nuts and bolts of several dozen tests, this book also has a section with entries on the more common medical conditions that the tests are used to identify or diagnose.
Overall, if you want to have more control over your health-care decisions, then this book is for you.
WHAT ARE MEDICAL TESTS?
Medical tests are a type of medical procedure that are prescribed for a variety of reasons, including diagnosing a specific disease or type of related condition, screening for disease, evaluating the severity of a disease, and monitoring the response to treatment. Frequently doctors will also order tests as a preventive measure as part of a routine examination to make sure everything is all right.
Tests can be performed to accomplish more than one purpose; for example, a blood test may reveal the presence of an infection, and it can also show whether a treatment is effective. Similarly, various types of scans may both identify an abnormality and also help your doctor monitor the efficacy of any therapy.
Types of Medical Tests
Depending on the source, medical tests can be classified into many different categories. We have chosen seven: analysis of body fluids, imaging, endoscopy, measurement of body functions, biopsy, genetic material analysis, and screening. Sometimes a test seems to qualify for more than one category; for example, endoscopy of the stomach lets clinicians examine the inside of the stomach and also capture a biopsy sample. Here is a brief explanation of the different types of medical tests:
Analysis of body fluids: Tests in this category involve the collection and analysis of blood, urine, cerebrospinal fluid (the fluid that surrounds the brain and spinal cord), saliva, sperm, vaginal fluids, digestive juices, and fluids that may collect in the stomach or near the lungs as a result of disease. A complete blood count (CBC) is probably the most commonly recognized test in this group.
Imaging: Regular X-rays are the most common type of imaging tests, but many other more sophisticated tests are often prescribed, including ultrasound, nuclear (radioisotope) scans, magnetic resonance imaging (MRI), positron-emission tomography (PET) scans, and computed tomography (CT) scans. These tests are designed to provide clinicians with images of the inside of the body.
Endoscopy: These tests utilize a special tube that usually has a camera and light at the tip. The tube is inserted into the body, usually through an existing body opening, and images of organs or cavities (spaces) are then viewed on a monitor by a clinician. Most endoscopes are flexible, although a few types are rigid. Some endoscopic procedures require tools be passed through the endoscope to remove tissue samples (biopsy).
Measurement of body functions: How is your heart functioning? How about your kidneys? There are a wide range of tests that record and analyze the activity of various body organs. An electrocardiogram (EKG), for example, measures the electrical activity of the heart, while an electroencephalogram (EEG) records the electrical activity of the brain.
Biopsy: A biopsy involves removing tissue samples from inside or outside the body and then examining them under a microscope. Tissues that are examined most often include skin, breast, liver, bone, kidney, and lung.
Genetic material analysis: Tests in this category involve evaluating cells from blood, skin, or bone marrow to see if there are any abnormalities in the genes, chromosomes, or both. Genetic testing is typically done in children and young adults to determine if they have a disease or are at risk of a disease, while adults may choose genetic testing to identify the likelihood of their children being born with or developing certain diseases.
Screening: Tests in this category are used to detect disease and other medical conditions in people who have no symptoms, and so it is easy to see why they often can be found in more than one category. Mammography, for example, is used for breast cancer screening, but is also considered an imaging test. Other types of screening tests include those that evaluate hearing and vision. Screening tests are designed to be sensitive (have the ability to detect many problems) but not specific (cannot identify the actual disease). That's why if the results of a screening test are positive, your doctor will schedule additional, more specific testing to identify the disease.
MEDICAL TESTS AND DEFENSIVE MEDICINE
Because they fear they will miss a diagnosis and expose themselves to malpractice lawsuits, many doctors are ordering expensive and unnecessary medical tests. This practice, known as defensive medicine, is estimated to cost more than $100 billion per year. One recent study shows that the next time you go into your doctor's office, you have a 43 percent chance of being ordered an unnecessary test. In many cases, patients end up paying for these tests because insurance companies are refusing to pick up the costs and/or because of increasingly rising copayment requirements.
What can you do? To protect yourself against undergoing costly, unneeded medical tests, ask yourself, your doctor, and a second physician (if you are not satisfied with the information you've gathered thus far) these questions before you agree to a test:
Why is this test needed? Some doctors, for example, are known to order a computed tomography (CT) or magnetic resonance imaging (MRI) scan for every patient who complains of a headache. Yet brain tumors are rarely found in people who have headaches, so these tests are rarely necessary.
Will the test results give the doctor information that will help him or her make decisive treatment decisions? Or will another test — or no test at all — provide enough information?
How much does this test cost? Remember, you may end up paying for the test.
What risks do I expose myself to if I do not have this test?
What alternative tests are available that will provide the same or similar information? Often a less expensive and/or less invasive test can provide the doctor the information he or she needs.
HOW RELIABLE ARE MEDICAL TEST RESULTS?
As we noted previously, one of the criteria for the tests chosen to be included in this book was reliability. Nothing is perfect, and that holds true for the reliability of diagnostic and screening tests, the results of which can vary widely depending on various factors. However, we selected tests that have been shown to be as accurate, precise, sensitive, and specific as possible when done correctly. In many of the entries, we have noted circumstances that may make a particular test less reliable. For example, obesity can make the results of an abdominal ultrasound less accurate, and smoking cigarettes before an illicit drug test may compromise the reliability of this test. Now let's look at some of the factors that can impact the reliability of medical tests.
Four indicators are usually used to determine the reliability of clinical lab tests. Accuracy and precision both indicate how well the test method performs day to day in a laboratory. Sensitivity and specificity involve how well the test is able to distinguish whether a disease is present or absent in the person tested. Laboratory tests are designed to be as precise, accurate, sensitive, and specific as possible.
Let's consider precision. A test is said to be precise when it can be repeated many times on the same sample and give similar results each time. That means the amount of random variation among the results is small and the test is said to have good "repeatability."
A test method's accuracy is determined by how close the test value is to the absolute "true" value of the substance being measured. Results from every test that is done are compared to established control specimens that have undergone many evaluations and compared to the gold standard for that test.
We would all like to have tests that are 100 percent accurate and 100 percent precise, but in reality small discrepancies can occur. That's because there are some variations between laboratories and their methods, instrumentation, and level of staff training. This is one reason why if you have a test repeated for any reason, your doctor will want to use the same laboratory, to avoid introducing any variation in precision and accuracy.
The two critical components that determine a test's accuracy are sensitivity and specificity. Sensitivity is the probability that a test is positive, assuming that the person being tested has the disease. Therefore, a certain test may have proven to be 95 percent sensitive. If 100 people are known to have a certain disease, the test that identifies that disease will do so correctly for 95 of the 100 people tested. The other five people tested will not show the expected result for the test. For that 5 percent, the test result of "normal" will actually be an incorrect, false-negative result. That means those five people will believe they are disease free when in fact they are not. The more sensitive a test is, the fewer false-negative results it will produce. That's why clinicians want the most sensitive diagnostic tests possible. In many cases, if a person gets a test result that the doctor suspects may be a false-negative result, he or she may order another — often different — test to verify the first results.
Specificity is the ability of a test to correctly eliminate people who do not have a certain disease or condition. For example, a certain test may have proven to be 93 percent specific. If 100 healthy individuals are given the test, only 93 of the 100 will be found "normal" or get negative results (be disease free). The remaining seven people (who do not have the disease) will get positive test results. For these seven people (7%), their "abnormal" findings are false-positive results.
Obviously, getting a false-positive test result is a problem, because no one wants to be treated for a disease that he or she does not have. Therefore, people who get a positive test result should contact their doctor to discuss the possibility that their results are a false-positive if they suspect the results may be in error, and ask what other testing they should have done to verify the results.
ONE LAST NOTE: THINK AHEAD
A question people need to ask themselves before undergoing a medical test is, What will I do with the information? When you and your doctor discuss your medical condition and any tests he or she may order, you should also discuss the treatment options you will have, depending on the results of the test(s). If, for example, your doctor orders a complete blood count because you may have anemia, you should know what treatment strategies are available to you. If you do not want to follow any of the doctor's treatment recommendations, even if you are told you have anemia, then you may want to think twice about having the test, or just have the test for your own information or until you change your mind about treatment.
In some cases, treatment options may include surgical procedures or additional testing. If you are undergoing a bronchoscopy and there is a possibility that you have lung cancer, you may want to think about researching surgeons in your area. If you are undergoing an amniocentesis because there is a possibility you are carrying a child with a genetic disorder, you should have a list of genetic counselors at your disposal so you can discuss your options with a knowledgeable individual.
The bottom line is that you should think carefully about any medical test you take: why and if you need it, how to prepare for it, what the risks are, and what you will do with the results. This book will help you with these questions.CHAPTER 2
25 COMMON MEDICAL TESTS
Why Do I Need This Test?
An abdominal ultrasound is an imaging test that uses high-frequency sound waves (rather than the ionizing radiation used in X-rays) to produce pictures of the organs and other structures in the upper abdomen. The test is used to evaluate the abdominal aorta and other blood vessels in the abdomen, kidneys, liver, gallbladder, pancreas, and spleen. An abdominal ultrasound can help diagnose various problems, including abdominal pain, an enlarged abdomen, kidney stones, stones in the gallbladder, abnormal liver function, urinary blockage, trauma to the abdomen, an obvious or suspected abdominal mass, and an abdominal aortic aneurysm (symptoms include belly or chest pain, pulsating sensation in the abdomen). Sometimes an abdominal ultrasound is used to help clinicians perform needle biopsies, in which needles are used to take tissue samples from any of the organs mentioned above.
In some cases, doctors also do a Doppler ultrasound study as part of an abdominal ultrasound examination. Doppler ultrasound is a special technique that evaluates how blood flows through a blood vessel, including the major arteries and veins in the abdomen, legs, neck, and arms.
What Will the Results Tell Me?
Your clinician will be able to observe and evaluate the presence of blood clots or other blockages to blood flow, presence of tumors or congenital abnormalities, and narrowing of blood vessels. Possible conditions an abdominal ultrasound can reveal include abdominal aortic aneurysm, cholecystitis (inflammation of the gallbladder caused by stones in that organ), gallstones, hydronephrosis (swollen or distended kidney), kidney stones, splenomegaly (enlarged spleen), or pancreatitis.
Excerpted from 25 Medical Tests Your Doctor Should Tell You About ... And 15 You Can Do Yourself by Deborah Mitchell. Copyright © 2010 Lynn Sonberg Book Associates. Excerpted by permission of St. Martin's Press.
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