Background The Centers for Disease Control recommends routine HIV testing in clinical settings. The evidence for an increase in HIV diagnoses as a result of these testing programmes is inconclusive. We examined the North Carolina (NC) expanded HIV testing programme’s impact on HIV testing and the diagnosis of new HIV-positive cases in sexually-transmitted disease (STD) clinics.

Methods The NC expanded HIV testing programme implemented routine, opt-out HIV testing in STD clinics in November 2007. All persons aged 18–65 who were tested for HIV in NC STD clinics July 2005-June 2011 were analysed. The monthly change in the number of HIV tests performed, number of new HIV-positive cases identified, and HIV positivity proportion per 1000 tests before and after the intervention were evaluated. Interrupted time series analysis with autoregressive components was used to account for underlying temporal trends and autocorrelation.

Results From July 2005-June 2011, 414,612 HIV tests were performed, yielding 1293 new HIV cases (0.3%). Prior to the intervention, the number of HIV tests performed increased by 60 tests per month (rate difference [RD] = 60.4, 95% confidence interval [CI]: 50.6, 70.2). However, after the intervention, the monthly increase in testing slowed to 42 tests per month (RD = 41.7, 95% CI: 36.8, 46.6). After the introduction of the intervention, neither the number of new HIV-positive cases identified nor the HIV positivity per month differed from expected case detection trends without the intervention (number of new HIV-positive cases: RD = –0.11, 95% CI: –0.33, 0.11; HIV positivity per 1000 tests: RD = 0.04, 95% CI:-0.001, 0.073).

Conclusion Despite the introduction of an expanded HIV testing programme in NC STD clinics, no change in HIV testing or HIV case detection was observed. A lack of evidence for programme yield in a clinical setting with high baseline levels of HIV testing questions the intervention’s appropriateness.