The “behind-the-knee” test for menstrual tampon irritation

Colposcopic inspection of the vagina is a routine component of the safety assessment of intravaginal products. However, colposcopic findings occur frequently in healthy women, raising questions about their relevance to intravaginal product safety. Practical disadvantages limit the utility of colposcopy for evaluating menstrual tampons, among them the presence of background microtrauma, the inability to assess effects during menstruation, and, importantly, the question of whether post-hoc assessments are sufficiently sensitive to detect small inflammatory changes. The Behind-the-knee (BTK) test is an alternative for evaluating inflammatory and tissue dryness effects of physical articles by their repeated application to the popliteal fossa under an elastic bandage. It enables concurrent parallel comparisons of experimental and control articles over time and substantially increases the sensitivity of detecting small changes in tissue inflammation. With this protocol, uncompressed experimental and control tampons yielded comparable relative and absolute erythema scores (after overnight recovery) as did colposcopic assessment of the lower genital tract 3 to 48 hours after menstrual use. Scoring erythema in the BTK test immediately after product removal increased the level of visually discernible inflammation 6-fold. In a study of commercial menstrual pads, subclinical inflammation visualized with cross-polarized light correlated with the frequency of subjective reports of discomfort during the test and discriminated the relative tolerability of the two products determined by market surveillance, providing added confidence in the predictive value of the test. We believe the BTK test to be a valuable alternative to colposcopy for assessing inflammation and dryness associated with menstrual tampons.