Medical testing centers have plenty of business these days -- perhaps more than they can properly handle. Prompted by fears of everything from AIDS and Lyme disease to high cholesterol, record numbers of people are lining up to give a blood sample and get back the good news, or bad. Too frequently, though, the news is just plain wrong. Several recent studies have revealed disturbing sloppiness or simple error in the way some blood tests are conducted and interpreted.
Among the worst offenders are public cholesterol-screening programs. Such centers, already a familiar sight in supermarkets and shopping malls in some parts of the U.S., may become even more common in the wake of a Government report issued last week. The report recommended a low-fat, low-cholesterol diet for everyone, not just those at risk for heart disease.
In a study of four public cholesterol-screening programs, published last week in the Journal of the American Medical Association, researchers found that only one produced accurate results consistently. The worst program was off the mark in almost 25% of the tests. A recent survey by the Department of Health and Human Services of such mass operations found that the "technicians" conducting the tests often had little or no training. More than half the people screened at 71 sites had their fingers squeezed, or "milked," to draw blood. This is known to dilute the blood with other fluids and produce an artificially low cholesterol reading. Says HHS inspector general Richard Kusserow: "Sometimes these operations looked more like a sideshow at a carnival." When blood is drawn in a medical setting by trained personnel, such error is less likely.
Lyme-disease tests can be inaccurate, even if carried out by experienced professionals. In a study reported in J.A.M.A., blood from the same 101 people was taken to three testing centers. One lab found 23 cases of Lyme, but the second discovered 31 cases, and the third came up with 43. The main problem is a failure to standardize Lyme tests from lab to lab.
Tests for AIDS are more accurate, but problems have arisen in reporting the results. In a study of 13 labs in the Western U.S., researchers discovered that written test results often contained misleading information. Several lab forms incorrectly stated that a positive result meant only that one had been "exposed" to the virus. In fact, it means that one is infected. The authors of the report said such imprecision could confuse doctors, particularly those having little experience with AIDS.
Stricter U.S. regulations on laboratory procedures are scheduled to go into effect this year, and the Government will increase the number of labs being inspected nationwide from 12,000 to 300,000. But the task is enormous, and many labs may still escape the enhanced surveillance. So anyone troubled by the results of a cholesterol test or other blood exam might be smart to follow that age-old advice applying to medicine in general: get a second opinion.