Objectives: To determine whether applicator staining could be incorporated into a microbicide study as a marker of adherence.
Goal: To test whether observers could identify intravaginally inserted applicators and compare the observers’ ratings to subjects’ self reports.
Study Design: Subjects participating in a 14-day microbicide trial to assess the safety of 0.5% PRO 2000 or matched placebo gel returned used and unused applicators. Each applicator was individually dyed or batched and immersed in a 0.4% trypan blue waterbath. Masked observers rated the applicators as intravaginally inserted or not; results were compared to subjects’ self-reports. To determine if the dye would allow observers to differentiate whether applicators had been filled before intravaginal insertion, staff either filled applicators and discarded gel ex vivo or asked volunteers to intravaginally insert applicators without gel and mixed these with a random sampling of used and unused study samples.
Results: 358 of 360 applicators were returned; 306 were reported to have been vaginally inserted and 52 unused. Observers agreed with the participant’s self reports in 98–99% of cases. No differences were observed between applicators stained individually or in batches. The ability to distinguish between applicators that were presumed to have been used properly, intravaginally inserted without gel, filled with gel and emptied ex vivo, or unused ranged from 76 to 87%.
Conclusions: Staining of applicators is accurate, inexpensive, and correlated well with self-report in a study of short duration. This method could prove useful in assessing adherence to product dosing in future microbicide trials.