KMJ WALLER1, NL DE LA MATA1, KR WYBURN2,3, PJ KELLY1, WD RAWLINSON4, AC WEBSTER1,5,6
1Sydney School of Public Heath, University of Sydney, Camperdown, NSW; 2Sydney Medical School, University of Sydney, Camperdown, NSW; 3Department of Renal Medicine, Royal Prince Alfred Hospital, Camperdown, NSW; 4Serology and Virology Division, South Eastern Area Laboratory Services (SEALS) Pathology, North Prince of Wales Hospital, Randwick, NSW; 5Centre for Transplant and Renal Research, Westmead Hospital, Westmead NSW; 6Centre for Kidney Research, The Children’s Hospital at Westmead, Westmead, NSW, Australia
Aim: To estimate the prevalence and incidence of HIV among increased risk groups in Australia, and subsequently estimate the absolute risk of window period infection.
Background: Referrals with increased risk behaviours that test negative for blood borne viruses may be suitable donors, however infections contracted during the window period (the period between infection and tests becoming positive) of detection may pose risk to recipients.
Methods: We performed a systematic review and meta-analysis. Published studies which examined HIV seroepidemiology in increased risk groups, namely men who have sex with men (MSM), intravenous drug users (IVDU) and prisoners, in Australia, were eligible. Pooled prevalence and incidence rates were estimated from available data. The probability of window period infection was estimated by assuming days since infection followed an exponential distribution, where window period for ELISA was 22 days and nucleic acid testing (NAT) was 7 days.
Results: We included 10 studies (73,014 participants). The estimated pooled incidence in MSM was 1.0 (95% CI: 0.9-1.2) per 100 person-years (pys), prisoners was 0.2 (95% CI: 0.1-0.4) per 100 pys and IVDU was 0.3 (95% CI: 0.2-0.3) per 100 pys. The risk of window period infection was highest among MSM at 6.2 (95% CI: 5.3-7.3) per 10,000 with negative ELISA, and 2.0 (95% CI: 1.7-2.3) per 10,000 with negative NAT and ELISA.
Conclusions: The predicted risk of window period HIV infection was relatively low among MSM, prisoners and IVDU, and was lower with negative NAT than ELISA alone. Where acceptable to patients, this low residual risk of infection transmission may allow increased opportunities for donation from increased risk referrals with negative testing.