Diagnostic bias and toxic shock syndrome.

Diagnostic bias could have occurred in the tampon/toxic shock syndrome association if the original diagnostic judgments by physicians or the subsequent diagnostic selections by investigators were influenced by knowledge of the patient's gender, menstrual history, or catamenial product. To determine whether such diagnostic bias can occur, a set of descriptive vignettes was prepared for six cases (Series X) having diverse resemblances to toxic shock syndrome or Kawasaki's disease. For each vignette in Series X, a paired case in a complementary Series Y was described in identical text except for different information about gender, menstrual history, or tampon use. Either Series X or Series Y was sent to a randomly selected sample of internists, family practitioners, and infectious disease subspecialists. The physicians were asked to provide a diagnosis for each case, using their own nomenclature or choosing from a list of 22 diagnostic possibilities. Six weeks later, respondents were asked to provide diagnoses for the complementary series of cases. Regardless of medical specialty or type of series received first, the 368 responding physicians were more likely to diagnose toxic shock for menstruating tampon-users or menstruating women than for non-menstruating women or men. In the most striking difference, toxic shock was diagnosed in 85 percent of instances when the case was described in a menstruating tampon-user, but in 23 percent of instances when the same case was described in a man (odds ratio = 18.8). Since the current epidemiologic data may be seriously distorted by diagnostic bias, the results indicate the need for scientifically valid investigations of the toxic shock syndrome/tampon relationship.