Changing the deferral for men who have sex with men – an improved model to estimate HIV residual risk

Abstract

Background and Objectives Eight published studies modelled the impact of changing from a lifetime to time‐limited deferral for men who have sex with men (MSM); each predicted greater risk impact than has been observed. This study uses these previous efforts to develop an ‘optimized’ model to inform future changes to MSM deferrals. Materials and Methods HIV residual risk was calculated using observed HIV incidence/prevalence prior to the change in MSM deferral, then with the additional MSM expected under a 12‐month deferral for five compliance scenarios, and finally using data observed after implementation of the deferral. Monte Carlo simulation calculated 95% confidence intervals (CI). Results The architecture of reviewed models was sound, and two were selected for combination into the optimized model. HIV risk estimated by this in the UK under MSM lifetime deferral was 0·102 (95% CI: 0·050–0·172) per million. The model predicted from a 27·8% decrease to a 47·6% increase depending upon compliance pre‐implementation of the 12‐month deferral. A decrease of 0·9% was observed post‐implementation. For Canada, HIV risk under a 5‐year deferral was 0·050 (95% CI: 0·00003–0·122) per million. Pre‐implementation of the 12‐month deferral, the model predicted from 30·2% decrease to 10‐fold increase. A decrease of 47·0% was observed after implementation. Conclusion The optimized model predicted HIV risk under 12‐month MSM deferral in UK and Canada would remain low, and this was confirmed post‐implementation. While the model is adaptable to other deferral scenarios, improved data quality would improve precision, particularly estimates of incidence in individuals likely to donate.

HIV residual risk in Canada under a three‐month deferral for men who have sex with men

“…Our model was based on the English model with the added feature of simulation to take into account the uncertainty and variability of parameters to estimate residual risk and 95% confidence intervals. Using this optimized model, we previously reported that the 12‐month deferral expected residual risk was not significantly different from the observed English and Canadian post‐implementation residual risk . The model assumes release errors will be negligible, thus does not estimate risk under conditions of emergency manual product release.…”

“…We have recently published a mathematical model that combined a published English deterministic model with stochastic Monte Carlo simulation to estimate risk with a 12‐month MSM deferral . That estimate used donor baseline data and input parameters based on the best available public health data, albeit very conservative.…”

The evolving blood donor deferral policy for men who have sex with men: impact on the risk of HIV transmission by transfusion in France

“…In addition, we considered the risk associated with only the window period, without taking into account any risk linked to testing and processing failures, as other studies have done . The false‐negative test rate was estimated at 0.05% in the United States and more recently at 0.04% in Great Britain .…”

“…In addition, we considered the risk associated with only the window period, without taking into account any risk linked to testing and processing failures, as other studies have done. [31][32][33] The false-negative test rate was estimated at 0.05% in the United States and more recently at 0.04% in Great Britain. 31,34 Applying a rate of 0.04% to that of confirmed HIV-positive donations between July 2016 and December 2017 (0.068 per 10,000 donations), the risk of an HIV-positive donation following a testing error was estimated at 0.0028 per 1 million donations, which is negligible.…”

A novel virus transforms blood transfusion

“…Numerous changes in blood policy in the US and internationally emanated from the federally-commissioned Institute of Medicine (IOM) Report. 6 Still other policies were developed in reaction to the hundreds of lawsuits in the US and the criminal proceedings in a number of countries including Canada and France. Canada reorganized its entire blood system as a consequence of the Royal Commission of Inquiry on the Blood System in Canada (Krever Commission).…”