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Michael Kanter, MD
Los Angeles

JAMA. 1986;255(6):743.

	Since this article does not have an abstract, we have provided the first 150 words of the full text PDF and any section headings.

To the Editor.—

In the recent article, "Status Report on the Acquired Immunodeficiency Syndrome," the Council on Scientific Affairs¹ calculated that testing blood components for human T-cell lymphotropic virus type III (HTLV-III) using Abbott Laboratories' enzyme-linked immunosorbent assay kit would result in 20,000 positive results annually. This calculation assumed there are 20 million blood donors annually and a prevalence rate of HTLV-III antibody in the general population of 0.1%. Unfortunately, the number of donors (D) multiplied by the prevalence of the antibody (P) equals the number of persons with HTLV-III antibody, not the number of positive test results, as these authors concluded. The number of positive results in fact is the sum of the number of true-positives plus the number of false-positives.

Standard probability theory² shows that true-positive equals D x P x sensitivity and false-positive equals D(1—P)(1—specificity). Thus, the expected number of positive results equals D x P . . . [Full Text PDF of this Article]

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