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Tag: Screenings

Don’t Try This at Home: The Mathematics of HIV Testing in Low-Risk Populations

This post considers potential pitfalls of home HIV testing. It provides an excuse to write a slightly less nerdy column on the mathematics of screening tests.

My friend and co-author A. David Paltiel flew in from Yale to speak with my University of Chicago students. David is a national authority on medical cost-effectiveness, particularly in matters connected with HIV. For example, this beautiful New England Journal of Medicine piece showed that population HIV screening is surprisingly cost-effective, even in relatively low-risk populations. In significant measure due to this analysis, the Centers for Disease Control and Prevention modified national guidelines to promote much more aggressive HIV screening in a variety of settings. So if your primary care doctor or emergency department nurse asks you whether you’d like an HIV test–blame Paltiel.

David and I have published related work on issues surrounding home HIV tests, now under FDA review. (See a great earlier commentary by Walensky and Paltiel here.) To simplify things, the idea here is that you could go to your local Walgreen’s and buy a test kit for about $40. You swab the thing around your mouth. In about 20 minutes, with impressive “accuracy” (in a minute I’ll explain why the commonsense word “accuracy” is a slippery way to describe screening tests), the test will say whether you are HIV-infected.

One natural group of customers might be romantically-involved University of Chicago students: They go out on a date. It goes well. They buy a pair of test kits (maybe romantically sharing one) for a quick HIV test. If the tests come out well…. whatever one cares to happen can now proceed.

Is this test a good idea? In some ways, yes. This normalizes testing. Some people will get tested who would not otherwise obtain care. But there are a variety of reasons to worry. One issue concerns the ability of ordinary people not to mess the test up. A second issue concerns whether home HIV tests will lead people to avoid other medical and public health systems that could provide better counseling and (if needed) stronger post-test linkages to care.

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If You Feel OK, Maybe You Are OK

Early diagnosis has become one of the most fundamental precepts of modern medicine. It goes something like this: The best way to keep people healthy is to find out if they have (pick one) heart disease, autism, glaucoma, diabetes, vascular problems, osteoporosis or, of course, cancer — early. And the way to find these conditions early is through screening.

It is a precept that resonates with the intuition of the general public: obviously it’s better to catch and deal with problems as soon as possible. A study published with much fanfare in The New England Journal of Medicine last week contained what researchers called the best evidence yet that colonoscopies reduce deaths from colon cancer.

Recently, however, there have been rumblings within the medical profession that suggest that the enthusiasm for early diagnosis may be waning. Most prominent are recommendations against prostate cancer screening for healthy men and for reducing the frequency of breast and cervical cancer screening. Some experts even cautioned against the recent colonoscopy results, pointing out that the study participants were probably much healthier than the general population, which would make them less likely to die of colon cancer. In addition there is a concern about too much detection and treatment of early diabetes, a growing appreciation that autism has been too broadly defined and skepticism toward new guidelines for universal cholesterol screening of children.

The basic strategy behind early diagnosis is to encourage the well to get examined — to determine if they are not, in fact, sick. But is looking hard for things to be wrong a good way to promote health? The truth is, the fastest way to get heart disease, autism, glaucoma, diabetes, vascular problems, osteoporosis or cancer … is to be screened for it. In other words, the problem is overdiagnosis and overtreatment.

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