Introduction: Participant's adherence to use of study product is a major concern in microbicide clinical trials, which can impact on proving product efficacy. In a previously described assay, single-use microbicide applicators exposed to the vagina were tested by spraying the applicator with trypan blue dye, resulting in vaginal mucus staining on inserted applicators. As subjects in our Phase 3 trials return applicators only at quarterly visits, often mixing inserted and not-inserted applicators together in the same bag, cross-contamination could confound results. In addition, trypan blue is carcinogenic and thus potentially hazardous to technicians spraying daily.
Methods: Applicators that were exposed to the vagina were placed in the same bag as unexposed applicators and shaken daily for up to 4 months. Validation was carried out in three clinical sites in South Africa.
Results: Trypan blue was replaced with FD&C Blue #1 granular food dye. Cross-contamination did not occur, nor did the length of time affect reaction to dye. In South Africa, the assay was validated with an accuracy of over 95%.
Conclusion: Applicator assay modifications render the test safe and suitable for use in clinical trials.