Price, performance, and the FDA approval process: the example of home HIV testing

Abstract

The Food and Drug Administration (FDA) is considering approval of an over-the-counter, rapid HIV test for home use. To support its decision, the FDA seeks evidence of the test's performance. It has asked the manufacturer to conduct field studies of the test's sensitivity and specificity when employed by untrained users. In this article, the authors argue that additional information should be sought to evaluate the prevalence of undetected HIV in the end-user

Population: The analytic framework produces the elementary but counterintuitive finding that the performance of the home HIV test- measured in terms of its ability to correctly detect the presence and absence of HIV infection among the people who purchase it-depends critically on the manufacturer's retail price. This finding has profound implications for the FDA's approval process.

FIGURE 1. Relationship of prevalence and price

The figure depicts the relationship between the price of home HIV test and the prevalence of HIV infection in persons willing to make a purchase at that price. The upper line denotes prevalence in the marginal consumer; the lower line represents prevalence in the average consumer. Under our linearity assumptions, the marginal consumer line has exactly half the slope of the average consumer line, reflecting the fact that the average test purchaser has substantially higher income than the consumer who is just willing to pay the specified price.

FIGURE 2. Positive predictive value for three different specificities

The figure illustrates the relationship between price and positive predictive value for a home HIV test with three possible levels of test specificity (99.6%, 99.7% and 99.8%). Each retains sensitivity= 99.7%.