Introduction

Much of health care revolves around the use of tests. Medical tests—some of which may also be referred to as procedures or studies—allow health care practitioners to gather information about a person's health and ability to function. Few medical tests are designed specifically for older people. But older people tend to undergo more medical tests in large part because they are at higher risk of developing many diseases. Moreover, older people, compared with younger people, often face very different challenges while preparing for and undergoing many medical tests. In addition, as people age, their test results and the way in which those results are interpreted often change.

Types of Medical Tests

Medical tests generally fall into one of six categories:

• Analysis of body fluids and contents
• Imaging tests
• Endoscopy
• Measurement of body functions
• Biopsy
• Analysis of genetic material in cells.

In many instances, two or more types of tests are combined in a single procedure, and the lines that separate the categories become blurred. For example, endoscopy of the stomach enables the examiner to view the inside of the stomach and obtain tissue samples for examination in a laboratory.

Analysis of body fluids and contents most often consists of tests of blood, urine, and the fluid that surrounds the spinal cord and brain (cerebrospinal fluid). Less often, fluids such as sweat and saliva and the contents of the digestive tract (for example, gastric juices and stool samples) are analyzed. In some instances, fluids being analyzed are present only in the case of disease. For example, in many liver diseases, fluid accumulates in the abdomen (ascites). In some lung diseases, fluid accumulates in the space between the membranes that surround the lungs (pleural effusion).

Imaging tests provide a picture of the inside of the body. Ordinary x-rays are the most common imaging tests. Others include mammograms, ultrasound scans, radioisotope (nuclear) scans, computed tomography (CT) scans, magnetic resonance imaging (MRI) scans, and positron emission tomography (PET) scans.

Endoscopy is the use of a tube to directly view the inside of body organs or spaces (cavities). Most endoscopes are flexible, although a limited number are rigid. The tip of the endoscope is usually equipped with a light and a camera so that the images can be seen simultaneously on a television monitor. Tools passed through a channel in the endoscope can be used to cut and remove tissue samples, destroy abnormal tissue, and close off bleeding blood vessels.

See the figure Viewing the Digestive Tract With an Endoscope.

The endoscope is usually passed through an existing body opening. For example, esophagogastroduodenoscopy (EGD) involves passing an endoscope through the mouth. Colonoscopy involves passing an endoscope through the anus. However, sometimes a small cut (incision) is made in the skin so that an endoscope can be passed into a body cavity. For example, arthroscopy involves passing an endoscope through an incision to view a joint, such as the knee.

Measurement of body functions often involves recording and analyzing the electrical activity of an organ. For example, electrical activity of the heart is measured with electrocardiography (ECG); and electrical activity of the brain is measured with electroencephalography (EEG). Other body functions that can be measured include how much and how fast air moves in and out of the lungs, the amount of blood pumped by the heart over a certain amount of time, and the ability of the kidneys to excrete waste products and excess water.

Biopsy involves examining tissue samples, usually with a microscope. This examination usually is used to determine the presence of abnormal cells that might provide evidence of inflammation or a cancer. Tissues commonly examined include skin, breast, lung, liver, kidney, and bone marrow.

Analysis of genetic material usually involves testing cells from skin, blood, or bone marrow. Older adults do not commonly undergo genetic testing for the purpose of determining whether they themselves have or are at increased risk of developing a disease. More often, they may undergo genetic testing to help determine the likelihood that their children or grandchildren will develop certain diseases.

Uses of Medical Tests

Medical tests have a variety of uses. Frequently, they are used to screen for or diagnose disease. Tests may also be used to determine the severity or extent of disease and to monitor how well a disease is responding to treatment.

Screening tests are designed to detect disease in people who do not have symptoms. For example, measuring the level of cholesterol may identify an abnormality that can increase the risk of a heart attack. Screening is usually performed when finding and treating a disease early is preferable to doing so later. Screening tests are most likely to be useful and widely accepted if they are accurate, pose few health risks, cause little or no discomfort, and are relatively inexpensive.

Diagnostic tests, on the other hand, are designed to confirm the presence of a disease when there is already suspicion or evidence that a person has the disease. For example, a doctor who suspects coronary artery disease in a person who gets chest pain during an exercise stress test might recommend cardiac angiography.

Cardiac angiography is not a good choice for screening because it can produce serious side effects, can be uncomfortable, and is expensive. These drawbacks are outweighed by the need for cardiac angiography, however, when the presence or absence of coronary artery disease must be confirmed.

Medical tests are also used to classify diseases into categories for the purpose of planning specific and effective treatment. For example, after a diagnosis of breast cancer is confirmed, additional tests are performed to determine if the cancer cells have special sites, called receptors, where estrogen attaches. The results influence decisions about which drugs to use to treat breast cancer.

Tests are sometimes used to monitor how well a person is responding to treatment. For example, blood tests are performed periodically in people with hypothyroidism to determine if the dosage of thyroid hormone replacement needs adjustment.

Certain tests lend themselves to both gathering information and treating disease. A colonoscopy, for example, may be done to detect abnormal growths, such as polyps, and then, if growths are found, to remove them immediately.

Making Decisions About Tests

Medical tests may give rise to a variety of questions. The best decisions about medical tests are reached when the doctor's experience and knowledge are combined with the person's knowledge, wishes, and values.

Most doctors rely heavily on their experience when recommending and ordering tests. Doctors learn more about tests by reading medical books and journals, consulting with colleagues, attending educational conferences, and referring to other resources, such as the Internet. They may also review recommendations (practice guidelines) published by groups of experts. In addition, doctors evaluate the results of research studies and consider how the findings might be applied.

People rely most heavily on their doctors for information on medical tests. Many people also turn to an ever-growing number of resources in print and on the Internet, but determining whether these resources are based on scientifically sound information can be challenging.

When deciding whether to recommend a screening test for a disease, the doctor estimates how likely it is that a person has the disease. The doctor considers whether the person has risk factors. The doctor may also consider how common the disease is in a population of people who have many of the same characteristics as the person (prevalence) and how many new cases of the disease occur during a specific period of time in that population (incidence). With this information, the doctor can then begin to select the best test with which to confirm or exclude the presence of the disease.

When deciding whether to perform a test, a doctor must consider what the range of possible results may mean. Unfortunately, medical tests are not perfect. Sometimes tests produce normal results in people who in fact have the disease (false-negative results). On the other hand, tests sometimes produce abnormal results in people who do not have the disease (false-positive results). Therefore, the doctor considers the test's sensitivity and specificity. Sensitivity is the likelihood that the test will produce abnormal results in people who do have the disease. Specificity is the likelihood that the test will produce normal results in people who do not have the disease.

A test must also be reliable. A reliable test gives the same result or nearly so when a person undergoes the test more than once under the same circumstances. In contrast, results from an unreliable test may change each time the test is done, making interpretation difficult or impossible.

A doctor must also consider how the results will be used. A test may not be warranted if the results will not change the recommended treatment plan. For example, if a test is being considered to determine the advisability of starting a particular treatment but the person and his doctor have already decided not to undergo that treatment, then the test need not be performed. Before performing a test, a doctor weighs the potential harm against the potential benefit.

Challenges Faced by Older People

Older people face a variety of challenges in preparing for and undergoing medical tests. Most tests, even many considered simple and safe, pose potential problems for older people. The higher risk of a problem occurring may be due in part to aging and to a higher likelihood of having one or more chronic diseases. The potential problems also depend on the specific test being considered. Few, if any, tests are problem free.

Following test instructions or understanding explanations may be difficult for some older people and may impede test taking. Such difficulty may arise because of vision or hearing loss. Written instructions may benefit some people. Large-print versions of written instructions may help, as may a simple voice amplifier. Memory or the ability to understand and follow instructions (cognition) may be impaired. People with severe cognitive impairment may become frightened or upset because they are not able to understand instructions or explanations. A family member or caregiver may need to remain with the person during testing to provide reassurance. Soft, soothing music played during the test may have a calming effect.

Problems with balance and moving around (mobility) may also affect testing. Older people are more likely to have diseases that interfere with balance and mobility. Decreased mobility and balance can make it difficult, for example, to get to the testing facility or to climb onto the tables used in magnetic resonance imaging (MRI) and computed tomography (CT) scanners. Testing may be made easier and safer if railings, assistive devices (such as walkers), and small portable steps or stools are available. Surroundings that are well lit also improve safety.

Chronic pain may make it difficult to lie motionless or to change positions during certain tests. Cushions or pillows may be used to reduce pain and pressure on a specific area of the body.

The fragile, thin skin of older people may be easily torn or cut in the process of moving on or off equipment. A bit of extra time and caution may be needed to avoid damaging the skin.

Questions to Ask the Doctor

An older person as well as family members and friends can become better informed about an upcoming medical test by asking the doctor the following questions:

• Why is the test being done?
• How is the test done?
• How do I prepare for the test?
• What can I expect to happen during and after the test?
• What are some potential problems that the test may cause?
• What are considered to be normal results?

The person may also want to know how long the test takes, what factors may affect test results, when test results will be available, and what may need to be done after the test results are known.

See the sidebar The Medical History and Physical Examination.