(P-BC-47) Optimal Timing for Hepatitis B Virus Detection: An analysis of 3 Versus 4 Months Post-Exposure

Background/Case Studies: In the context of harmonizing the deferral to a three-month period for all infectious risk factor, no studies have explored whether a 3-month deferral may be safely relaxed to 4 months regarding hepatitis B virus (HBV) infection. Therefore, this study examined how the probability of detecting a HBV infection by nucleic acid testing (NAT) differs at 3 versus 4 months post-exposure. The aim is to ascertain whether extending the testing window by one month significantly impacts detection rates, thus informing optimal testing protocols in blood screening.

Study

Design/Methods: This analysis was conducted within the framework of a probit analysis based on the Weusten model. The approach considered the characteristics of the NAT-HBV assay used at our blood service (Ultrio plus NAT test) alongside the viral dynamics of HBV infections. The impact of testing at 3 versus 4 months post-exposure was evaluated using a Monte-Carlo simulation, in which 10,000 infected donors were observed over 833 donor-years (our blood service detects ~12 HBV infections/year).

Results/Findings: Our analysis was anchored by a lognormal distribution and had a geometric mean of 2.6 days (min-max = 1-11days) for the doubling time of HBV during the ramp-up phase. The mean window period for a 95% detection probability was estimated at 34.5 days, with a range of 12.4‒136.5 days. Of the 10,000 simulated donors, 32 would test negative by NAT between 3 and 4 months post-exposure, which corresponds to one undetected infection every 26 years at our blood service.

Conclusions: According to our analysis, the probability of detecting HBV negligibly differs at 3 or 4 months post-exposure. Consequently, a 3-month deferral for NAT testing appears justified for HBV. This recommendation is further supported by ancillary factors (e.g., the growing prevalence of HBV vaccination) and the generally mild nature of HBV infections. Harmonizing the temporary deferral period at 3 months not only mitigates confusion among donors but also enhances the overall integrity of screening protocols. We invite further scrutiny and discussion regarding the implications of our risk assessment.