Background We sought to determine if pooled nucleic acid testing (pNAT) for HIV RNA would identify early HIV infections in stored samples collected in 2008 from Edmonton (Canada) patients who were: (1) Seronegative for HIV antibody (HIVAb-) at the STI clinic, and (2) Seropositive for syphilis (syphAb+) with no history of a positive HIV test.

Methods Using data from the Provincial Laboratory and STI clinic, an anonymized dataset with the last HIVAb- (HIVGO1/2, Abbott, AxSym +/- Western Blot) (STI clinic patients) or first syphAb+ (Architect, Abbott +/- RPR & Innolia) was constructed with: (1) All patients: age, gender, date of testing, N. gonorrhoea (NG) and C. trachomatis co-infection within 30 days of HIV/syphilis test, infectious syphilis stage, and HIV testing as of Dec 2010 and (2) STI clinic patients only: syphilis test results within 30 days of their HIVAb- test. Patients remaining HIVAb- > 180 days after the sample receipt date were excluded from HIV pNAT. The remaining samples were divided into SyphAb+ and SyphAb-subsets. Pools of 25 samples were tested using the Roche COBAS AmpliPrep/COBAS TaqMan HIV-1 Test (pNAT). Positive pools were broken down to identify positive individuals. Percentage calculations were based on patients with pNAT.

Results 7954 HIVAb- patients were eligible. Of these, 2237 were retested and were HIVAb- > 180 days; 216 (10%) of this subset were SyphAb+. 5441 (95%) of the remaining patients had samples available for pNAT: 5001 were SyphAb-, 331 were SyphAb+, and 109 had no syphilis testing. Four SyphAb+ patients (0.07% of all, 1.2% of SyphAb+), all seen at STI clinic, had detectable HIV RNA using pNAT; one patient had Early Latent Syphilis and positive NG culture.

Conclusions pNAT testing can be used to identify acute HIV infections in high risk populations. Patients with positive syphilis serology may be an important subset for this approach.