Impact of Expanded HIV Screening

IN RESPONSE:

We share Dr. Lander's concern regarding false-positive results with rapid HIV tests, especially in populations with low HIV prevalence, and we agree that guidelines for communicating findings to patients will be useful. However, we believe that his presentation of the issue is overstated. First, we deliberately accentuated the false-positive problem by adopting a conservative specificity assumption (97.5%). Today's rapid HIV tests have higher reported specificities (99.3% to 99.6%) and, therefore, have more favorable predictive values (1). Second, current approaches to screening for other chronic diseases (mammography for breast cancer, for example) suggest that diagnostic tests with high false-positive rates can be appropriately managed in the clinical setting (2). Practitioners can explain that whereas a negative result is a reliable indicator of the absence of HIV infection (setting aside the 3-month pre-seroconversion “window” period), an initial positive result is not conclusive for HIV but highlights the need for more specific tests.

Rapid HIV tests have similar sensitivity and specificity to standard antibody tests. They provide results within 20 minutes, eliminating the high rate of failure to return for results (25% in persons testing HIV-positive and 33% in persons testing HIV-negative at publicly funded U.S. clinics [3]). However, unlike standard antibody tests, rapid testing allows positive results to be reported to the patient before they can be confirmed by repeated tests and Western blots. The tradeoff is clear: Wait 1 or 2 weeks, knowing that up to one third of cases will be lost to follow-up, or report preliminary results to patients and link them to care, knowing that this may cause short-term distress in a small percentage of those tested. We find that the benefits of rapid testing more than offset the risks, even when we assume a low-specificity test and assign large economic and quality-of-life costs to false-positive findings.

We agree with Drs. Krentz and Gill that “cost-effective” does not mean “cheap” and that planners must account for the direct costs of providing medical care to newly diagnosed cases. We included these costs in our analysis. We, too, found that the economic impact of expanded HIV screening lies less in the cost of the test than in the downstream treatment costs triggered when a new case is diagnosed. This highlights the need for a coordinated, comprehensive commitment of resources, at both the state and federal levels, to finance expanded HIV screening on publicly funded HIV programs in the United States.