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Does More HIV Testing Identify More New HIV Cases?

Retrospective analysis of New York City registry data demonstrated that the proportion of newly identified HIV cases varied significantly across testing sites during a period of increased Western blot testing.

One goal of increased HIV testing is to identify more HIV-positive patients who are unaware of their status. To assess whether that goal is achieved, researchers focused on New York City, where testing conducted or funded by the health department has increased greatly in recent years. Specifically, they used the New York City HIV Surveillance Registry to retrospectively identify the percentage of positive Western blot tests, conducted from January 2004 through December 2006, that represented new HIV diagnoses. Tests had been performed at a variety of locations, including health-department and other city-run facilities.

Of 31,504 unique positive Western blot tests linked to 23,090 cases in the registry, only 11,600 (37%) represented newly diagnosed cases. Neither the overall number of positive tests nor the percentage of them that were new cases changed significantly from 2004 to 2006. However, the percentage that represented new cases did increase significantly at health-department sexually transmitted disease clinics (from 66% to 75%) and at some types of non–city-run sites.

The percentage of positive Western blot tests that represented new cases was significantly higher at health-department sites overall (64%) than at other city-run sites (42%) and non–city-run sites (34%). Within non–city-run sites, the percentage of positive tests that were new cases varied widely, from 12% at drug-treatment centers to 58% at private physicians’ offices. Of the positive tests in the 2006 registry, nearly two thirds were repeat positives, and most of those appeared to be from people who were initiating or reinitiating care.

Comment: Despite stepped-up efforts to increase HIV testing and improve detection of new HIV cases, this retrospective study did not document significant increases in total positive or diagnostic (new positive) Western blot tests at all testing sites in New York City. Some sites demonstrated decreased rates of diagnostic tests, whereas others, including some health-department and city-run sites, demonstrated increased rates. Interestingly, most positive tests in 2006 were repeat positives. Although the specific reasons for repeat testing could not be pinpointed, initiating or reinitiating care appeared to be the main ones. HIV testing programs must be evaluated to ensure that new cases are truly new — i.e., that they are not repeat positives.

— Sonia Nagy Chimienti, MD

Published in AIDS Clinical Care May 22, 2009

Citation(s):

Hanna DB et al. Most positive HIV Western blot tests do not diagnose new cases in New York City: Implications for HIV testing programs. J Acquir Immune Defic Syndr 2009 May 7; [e-pub ahead of print].