BED Estimates of HIV Incidence: Resolving the Differences, Making Things Simpler

<div><h3>Objective</h3><p>Develop a simple method for optimal estimation of HIV incidence using the BED capture enzyme immunoassay.</p> <h3>Design</h3><p>Use existing BED data to estimate mean recency duration, false recency rates and HIV incidence with reference to a fixed time period, <em>T</em>.</p> <h3>Methods</h3><p>Compare BED and cohort estimates of incidence referring to identical time frames. Generalize this approach to suggest a method for estimating HIV incidence from any cross-sectional survey.</p> <h3>Results</h3><p>Follow-up and BED analyses of the same, initially HIV negative, cases followed over the same set time period <em>T</em>, produce estimates of the same HIV incidence, permitting the estimation of the BED mean recency period for cases who have been HIV positive for less than <em>T</em>. Follow-up of HIV positive cases over <em>T</em>, similarly, provides estimates of the false-recent rate appropriate for <em>T</em>. Knowledge of these two parameters for a given population allows the estimation of HIV incidence during <em>T</em> by applying the BED method to samples from cross-sectional surveys. An algorithm is derived for providing these estimates, adjusted for the false-recent rate. The resulting estimator is identical to one derived independently using a more formal mathematical analysis. Adjustments improve the accuracy of HIV incidence estimates. Negative incidence estimates result from the use of inappropriate estimates of the false-recent rate and/or from sampling error, not from any error in the adjustment procedure.</p> <h3>Conclusions</h3><p>Referring all estimates of mean recency periods, false-recent rates and incidence estimates to a fixed period <em>T</em> simplifies estimation procedures and allows the development of a consistent method for producing adjusted estimates of HIV incidence of improved accuracy. Unadjusted BED estimates of incidence, based on life-time recency periods, would be both extremely difficult to produce and of doubtful value.</p>