Dr. Keith Roach

DEAR DR. ROACH: What do you think of the explosion in DIY home health care tests? — K.L.R.
ANSWER: Some of the home health care tests have had a major and beneficial impact on care. One easy example are at-home COVID tests, which allow people to get an answer of whether they have COVID very quickly. This potentially allows them to get emergency treatment and avoid infecting others.
The test itself is of a high quality, and a positive test result in a person with symptoms of COVID is virtually certain to mean a true infection. Unfortunately, a negative test still isn’t perfect; the person still may have COVID, and a good sample just wasn’t retrieved. (There is a small downside to at-home COVID testing, which is that it has made it much harder to tell how much COVID is circulating.)
Given the difficulties that many people have getting care, I can understand why people are interested in doing testing themselves. Unfortunately, there are some real problems with home testing:
One is that interpreting lab tests can be a challenge. I often get calls from my patients wondering why one of their lab tests was abnormal. For example, the complete blood count (CBC) with platelets and a differential has about 20 lab results, including ones like the absolute basophil count.
A laboratory usually defines “normal” as what healthy people have 95% of the time. This means that for any given test, about 5% of the time, a healthy person will have an abnormal test result. With a battery of individual tests like the CBC, this means that about 65% of the time, a healthy person will have at least one “abnormal” result, which is usually just out of the “normal” range.
This issue is particularly important with laboratory tests for rare conditions. Even with an excellent-quality laboratory running a test with a very good ability to detect diseases, most abnormal tests will be false positives, causing a person to have anxiety and incur expenses from further testing. It takes experience to know when to worry about abnormal test results.
That being said, there are quite a few times where home testing makes sense. A person with diabetes can do home A1C testing to know how urgent it is to see their diabetes provider. Home testing for INR levels in a person on warfarin makes their lives much easier by not having to go to the office every few weeks.
However, there is not always a high level of regulation among home-testing services, so the results from DIY tests might not be the same that they would be from a certified clinical laboratory. But laboratory error is still a possibility, and it can lead to confusion or anxiety in the case of false positives, as well as inappropriate reassurance in the case of false negatives.
I understand access to primary care providers is a huge problem for many in the United States, but DIY home testing is not a comprehensive solution for all.
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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.
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