Evaluation of 3 approaches for assessing adherence to vaginal gel application in clinical trials
Background: Accurate measurement of adherence to product use is an ongoing challenge in microbicide trials. Methods: We compared adherence estimates using 2 applicator tests (a dye stain assay [DSA] and an ultraviolet light assay [UVA]), the Wisebag (an applicator container that electronically tracks container openings), and self-reported adherence (ability, frequency, and percent missed doses). Healthy, HIV-negative, nonpregnant US women aged 23 to 45 years received a Wisebag and 32 applicators filled with placebo gel were instructed to insert 1 applicator daily for 30 days, returned the Wisebag and all applicators, and completed an exit interview. Emptied applicators were tested by UVA and then DSA, and scored by 2 blinded readers. Positive and negative controls were randomly included in applicator batches. Results: Among 42 women enrolled, 39 completed the study. Both DSA and UVA yielded similar sensitivity (97% and 95%) and specificity (79% and 79%). Two participants had fully inoperable Wisebags, and 9 had partially inoperable Wisebags. The proportion of participants considered to have high adherence ( ≥ 80%) varied: 43% (Wisebag), 46% (UVA), 49% (DSA), and 62% to 82% (self-reports). For estimating high adherence, Wisebag had a sensitivity of 76% (95% confidence interval, 50%–93%) and a specificity of 85% (95% confidence interval, 62%–97%) compared with DSA. Although 28% of participants reported forgetting to open the Wisebag daily, 59% said that it helped them remember gel use. Conclusions: Dye stain assay and UVA performed similarly. Compared with these tests, self-reports overestimated and Wisebag underestimated adherence. Although Wisebag may encourage gel use, the applicator tests currently seem more useful for measuring use in clinical trials.
van der Straten, Ariane, Helen Cheng, Barbara Mensch, Barbara Friedland, Lauren L. Katzen, Sarah A. Littlefield, Niall Buckley, Lilia Espinoza, Marla J. Keller, Betsy C. Herold, and Mark H. Einstein. 2013. "Evaluation of 3 approaches for assessing adherence to vaginal gel application in clinical trials," Sexually Transmitted Diseases 40(12): 950–956.