Optimal methods for collecting and storing vaginal specimens for prostate-specific antigen testing in research studies

BackgroundProstate-specific antigen (PSA) detected in vaginal fluid can be used in studies of HIV/sexually transmitted infection (STI) and pregnancy prevention as an alternative to relying on participant reports of exposure to semen. Optimal methods for collecting and storing specimens for this testing have not been determined.Study DesignWe conducted a controlled, in vitro experiment of 550 specimens spiked with semen to determine the effects of swab type (five types), storage conditions of the swabs (room temperature with or without desiccant or at − 80°C without desiccant) and time from collection to testing (seven intervals over the course of 12 months) on the identification of PSA. We performed factorial analysis of variance to identify factors influencing PSA detection.ResultsConcentrations of PSA detected in the swabs declined with time of storage over the 1-year experiment (p<.01). The 1-mL, rayon-tipped swab stored immediately at − 80°C following collection performed best.ConclusionsIf immediate testing or freezer storage is not feasible, investigators should use a swab with 1-mL capacity with processing and testing as soon as possible after specimen collection.