Background HIV testing remains one of the most effective HIV prevention interventions because most persons newly diagnosed with HIV alter their behaviours to reduce the risk of transmission to others. We examined temporal trends and correlates of the frequency of HIV testing among men who have sex with men (MSM) in King County, WA.

Methods We evaluated electronic medical records of MSM testing for HIV at the Public Health—Seattle & King County (PHSKC) STD Clinic. The intertest interval (ITI) was defined as the number of days between the last reported HIV test and the current visit. ITIs ≤30 days were not considered to be new tests. Correlates of the ITI were determined using Wilcoxon rank-sum tests, Spearman's correlation coefficients, and median regression.

Results Between 1 January 2003 and 7 December 2010, there were 13 637 HIV testing visits among MSM who reported a prior negative HIV test or did not know their status. These men reported a median ITI of 215 days (range: 31–8536; IQR: 124–409); 10 567 (77%) reported an ITI consistent with at least annual testing (<15 months) and 1693 (12%) reported no HIV test in the last 2 years. The median ITI decreased from 229 days in 2003 to 198 days in 2010 (p<0.001). Having sex with men only (vs men and women; p<0.0001), ≥10 male sex partners (p<0.0001), unprotected anal intercourse with a male partner of unknown or positive HIV status (p<0.0001), methamphetamine use (p=0.018), and poppers use (p<0.0001) in the last year were all associated with shorter ITIs, as were decreasing age (p<0.0001) and ever having been diagnosed with syphilis, gonorrhoea, or chlamydial infection (p<0.0001). Race, ethnicity, and injection drug use were not associated with ITI. In multivariate analyses, decreasing age, later visit year, sex with men only, ≥10 male sex partners in the last year, and history of bacterial STI remained associated with shorter ITIs (p<0.001 for all). The median ITI was longer in the 337 men (2.5%) newly diagnosed with HIV compared to those who tested HIV-negative (279 vs 213 days, respectively; p<0.0001).

Conclusions From 2003 to 2010, the median ITI among MSM attending the PHSKC STD Clinic was 215 days, and this has decreased over time. Encouragingly, MSM at highest risk for HIV acquisition have even shorter ITIs, although those newly diagnosed with HIV continue to have longer ITIs. Further efforts are needed to reduce the time that HIV-infected persons are unaware of their status.