Use of the dye stain assay and ultraviolet light test for assessing vaginal insertion of placebo-filled applicators before and after sex

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Article (peer-reviewed)

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Background: Applicator dye staining and ultraviolet (UV) light have been used in trials to measure adherence, but not in the setting of before and after sex gel dosing (BAT-24). This study was designed to determine if semen or presex gel dosing impacts the sensitivity and specificity of a dye stain assay (DSA) for measuring vaginal insertion of placebo-filled applicators with BAT-24 dosing. Methods: Healthy monogamous couples received Microlax-type applicators (Tectubes, Åstorp, Sweden) filled with hydroxyethylcelluose placebo gel. Women were instructed to vaginally insert 1 dose of gel before and a second dose after sex and to return applicators within 48 hours after sex. Applicators were stained to detect semen, followed by UV then DSA, and scored by 2 readers. Positive and negative controls were randomly included in applicator batches. Results: Fifteen couples completed the study. Each woman returned at least 6 applicators over a 30-day period. The sensitivity for insertion of postsex applicators was higher for UV (97%) compared with DSA (90%), and the specificity was similar ( ≥ 96%). For presex applicators, the sensitivity and specificity were higher for DSA (100%) compared with UV testing (87% sensitivity, 96% specificity). Among returned postsex applicators, 95% tested positive by UV compared with 87% by DSA. Agreement between readers was significantly better on the presex applicators for DSA than for UV, and for postsex readings, agreement was less than half that for UV, although the results were not statistically significant. Conclusions: Applicator tests are feasible for measuring adherence in trials with gel dosing before and after sex.