Background: The impact of routine, opt-out HIV testing programs in clinical settings is inconclusive. The objective of this study was to estimate the impact of an expanded, routine HIV testing program in North Carolina sexually transmitted disease (STD) clinics on HIV testing and case detection.

Methods: Adults aged 18 to 64 years who received an HIV test in a North Carolina STD clinic from July 1, 2005, through June 30, 2011, were included in this analysis, dichotomized at the date of implementation on November 1, 2007. HIV testing and case detection counts and rates were analyzed using interrupted time series analysis and Poisson and multilevel logistic regression.

Results: Preintervention, 426 new HIV-infected cases were identified from 128,029 tests (0.33%), whereas 816 new HIV-infected cases were found from 274,745 tests postintervention (0.30%). Preintervention, HIV testing increased by 55 tests per month (95% confidence interval [CI], 41–72), but only 34 tests per month (95% CI, 26–42) postintervention. Increases in HIV testing rates were most pronounced in women and non-Hispanic whites. A slight preintervention decline in case detection was mitigated by the intervention (mean difference, 0.01; 95% CI, −0.02 to 0.05). Increases in case detection rates were observed among women and non-Hispanic blacks.

Conclusions: The impact of a routine HIV screening in North Carolina STD clinics was marginal, with the greatest benefit among persons not traditionally targeted for HIV testing. The use of a preintervention comparison period identified important temporal trends that otherwise would have been ignored.