Home diagnostic tests: the ultimate house call? Screening tests often are used at home to checkfor symptoms of a disease when they may not be readily apparent

FDA Consumer, Nov-Dec, 2001 by Carol Lewis

More and more americans are playing doctor in the privacy of their own bathrooms, using a few drops of blood or a urine sample to test for cholesterol, blood glucose, or evidence of colon or rectal cancer. In fact, a snippet of a child's hair now can confirm the use of illicit drugs.

Often seen as a less expensive and a more convenient alternative to a trip to the doctor's office, self-testing diagnostic and monitoring devices are booming in sales. Devices such as blood-glucose tests and blood-pressure kits make it easier for people to self-monitor conditions such as diabetes and hypertension. However, this technology-driven trend is not without limits and could result in serious problems for those who rely on the tests instead of on the expertise of their health-care provider. A recent shift in the home diagnostics market--from monitoring chronic illnesses to diagnosing serious or potentially fatal diseases--is raising red flags among health professionals.

For years, pregnancy tests and ovulation predictors dominated the home test kit market. While these devices still generate large numbers of self-care sales, other tools of the medical trade are fast becoming available outside the doctor's office--no prescription needed. Spiraling health-care costs, increased interest in preventive health care, and a desire for privacy are paving the way for products that now include screening for the virus that causes AIDS and for drugs of abuse.

Screening tests often are used at home to check for symptoms of a disease when they may not be readily apparent. For example, people can measure their cholesterol and triglyceride levels--two types of fats in the blood--to help minimize the risk of cardiovascular disease.

Benefits and Limitations

Home test kits are, in many cases, as inexpensive as a co-payment to a doctor and a lot less time-consuming. Some can provide speedy results. Women often use home pregnancy test (HPT) kits for these reasons, as well as for the convenience of testing at home. Some women prefer to know for sure that they are pregnant before visiting their physicians, and HPT kits can help confirm pregnancy earlier. An earlier confirmation provides an opportunity for health-care providers to counsel women about their options, and to discourage potentially harmful behaviors, such as smoking and use of alcohol or drugs.

Kidney disease is one of the most devastating complications of diabetes, but it's also detectable and treatable in its earliest stages. A home test kit allows people with diabetes to test for glucose and even small amounts of protein in their urine--an early sign of kidney dysfunction.

Jim Watson, R.Ph., a pharmacist at the CVS pharmacy in Gaithersburg, Md., says that in his experience, blood glucose monitoring systems and home pregnancy tests are among the most popular tests purchased for home use.

"Diabetics already know they have the disease and so they test their blood sugar levels several times a day," he says. By contrast, Watson says, although women may only use a pregnancy test once, they are still one of the most popular tests the store sells. Sales of both HIV and drug screening home tests are infrequent, according to Watson.

One sign of their overall increasing popularity is the fact that many pharmacists are moving home test kits from behind their counters onto free-standing displays. The lure of the Internet is also helping to make these devices more readily available.

Steven Gutman, M.D., director of the Food and Drug Administration's clinical laboratory devices division, says that consumers need to be wary about buying and using the kits on their own. "People need to carefully read the test-kit labeling and instructions, where important information and warnings about the product are listed," he says. Among other things, this information tells how a test works, and what to do when it doesn't. Home test kits are meant to be an adjunct to doctor visits, not a replacement for them. "Although the menu of home testing products has expanded," Gutman says, "the advice is still the same."

See Your Doctor, Too

While convenience, confidentiality, and the cost-saving benefits of home testing cannot be overlooked, doctors are concerned about the availability of medical tests that encourage self-diagnosis because of the possibility that the results could be misinterpreted and treatment might be delayed.

For example, Sandy Stewart, Ph.D., a research biomedical engineer in the FDA's Center for Devices and Radiological Health (CDRH), says that blood pressure monitors should be used for tracking blood pressure readings between doctor's visits. "Users should never change their medications based on a home blood pressure reading." If there are significant changes, he says, the user should see his or her doctor immediately. "The blood pressure reading taken in the physician's office must be the final word."

In addition, the diagnostic value of home test kits can be affected by users who don't follow instructions carefully. In an effort to conceive a child, Donna Trossevin of Frederick, Md., bought from a local pharmacy an ovulation predictor that uses body temperature to help pinpoint a woman's most fertile time. Although the kit consisted of only a thermometer and special paper to chart her daily temperatures, Trossevin says it was difficult to get accurate readings because "if you don't hold the instrument just so, you can easily misread the numbers." And the half a degree increase from a person's normal temperature that a woman is looking for to predict ovulation "is such a small window of opportunity and easy to miss," says Trossevin. "I just never knew 100 percent whether I was ovulating or not."