Home Diagnostic Tests : Find a Reputable Source, Follow the Directions

by Food and Drug Administration (FDA)

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Those who rely on home tests also miss out on pre- and post-test counseling, which offer information, support, competence, interpretation, and follow-up advice to consumers that only a health-care professional can give. The benefit of having a health-care professional involved in a test or screening procedure is that the results can be evaluated within the context of the whole health picture, not just one test. Furthermore, receiving news of potential pregnancy, illness, or infection over the phone, or from the color of a test strip, can be devastating.

"The first 72 hours following a positive result for an illness as serious as HIV is when people are most likely to hurt themselves," says Edward Geraty, a licensed clinical social worker with Behavioral Science Associates in Baltimore. Geraty says it's important to have a face-to-face relationship when delivering the news of a positive HIV test. Without it, he says, "there's a psychological component of the person's illness that is completely left out of the process."

Bob Barret, Ph.D., agrees. A professor of counseling at the University of North Carolina at Charlotte, Barret believes that home test kits, particularly for HIV, "are best used only by those who are well-educated about the disease, and who are in touch with their emotions and have a good support system around them."

Find a Reputable Source

Accuracy, too, is an important consideration when it comes to home testing. False positive test results indicate that a condition is present when, in fact, it is not. False negatives are results that do not identify a condition that is present.

The Federal Trade Commission, which enforces consumer protection laws, recently reviewed results of several unapproved HIV test kits advertised and sold on the Internet for self-diagnosis at home. In every case, the kits showed a negative result when used on a known HIV-positive sample.

Similarly, the FDA recently tested a number of unapproved home HIV test kits sold on the Internet that were confiscated during a criminal investigation. None produced accurate results. In reality, the outcome could have had grave consequences for a user in terms of mental and emotional stress, access to proper medical treatment, and transmission of the disease to others. The FDA's Center for Biologics Evaluation and Research, which reviews all blood-related products, continues to investigate firms and people involved in the illegal sale of unapproved HIV home test kits in the United States.

Follow the Directions

Home test kits, for the most part, involve relatively simple procedures. Some are as straightforward as one pregnancy test in which chemically treated test strips dipped in urine produce colored indicator lines. Others require a finger prick and the placement of a blood sample onto a reagent strip. The strip is inserted into a machine that measures blood glucose levels. Still others, like the only FDA-cleared HIV home sample collection kit, consist of multiple components, ranging from pre-test counseling information to a personal identification number for obtaining the test's results. In any case, the FDA requires that the kits be simple enough for an average consumer to use at home without a doctor's supervision.

Some home tests give their results as positive or negative. Performance of these is described in terms of sensitivity — the probability that the results will be positive when a disease or condition is present; and specificity — the probability that the results will be negative when a disease or condition is not present. Other home tests give numerical results. Performance of these is described in terms of precision — how reproducible the results are when a test is run over and over; and accuracy — how well the results compare to a laboratory test. All diagnostic tests have limitations, and sometimes their use may produce erroneous or questionable results. Test results obtained at home can often be clarified by a physician, who may recommend another test that is handled by a laboratory.

Gutman, whose office is within CDRH, says that home test kits should not be stored in places where they might be exposed to extreme temperatures, since this may cause product deterioration over time. He also stresses the importance of checking test-kit expiration dates — chemicals in an outdated test may no longer work properly, so the results are not likely to be valid.

While manufacturers of professional test kits used in clinics and hospitals or doctor's offices are required to include sensitivity and specificity information in their labeling, the FDA does not make manufacturers of home test kits do so. But Lori Moore of Maysville, Ky., thinks they should.

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.