Measurement of Vaginal Microbicide Adherence Using Visual Inspection as Compared to Ultra Violet Light Assessment of Returned Empty Gel Applicators

Accurate and objective measurement of adherence is critical in microbicide trials. We compared two applicator tests: visual inspection of returned empty tenofovir gel applicators (VIREA) and ultraviolet light (UVL) assessment in terms of sensitivity and specificity, and for concordance. Sensitivity and specificity analysis of 24 control applicators (12 known-inserted and 12 sham-inserted) at 4-months after receipt was 75.0 and 66.7 % for VIREA and 83.3 and 91.7 % for UVL, respectively. After an additional 3 months of storage sensitivity and specificity was 100 and 58.3 % for VIREA and 100 and 66.7 % for UVL, respectively. In January 2015, 1316 empty applicators were returned as used by 115 participants enrolled at one site in a randomized controlled trial. Assessment outcomes showed 78.8 % agreement between the techniques. Methods concurred that 22.0 % of the returned empty applicators appeared unused. By UVL assessment, 40.0 % of returned empty applicators had no evidence of vaginal insertion, translating to a potential 28.0 % less product used as compared to that returned as used by women. UVL assessment may be considered a more accurate and less subjective measure of adherence as compared to VIREA.