Method of limits: Female genital stretch perception thresholds

INTRODUCTION: Women with pelvic organ prolapse describe vaginal laxity and poor sensation of vaginal tone that does not correlate with anatomical findings. This discrepancy could be explained by altered vaginal sensation and a test that could measure sensation of vaginal tone, transmitted via Aalpha and Abeta nerve fibers, would further our understanding of the pathophysiology of vaginal laxity. OBJECTIVE: To develop quantitative sensory testing (QST) for vaginal tone using genital stretch perception thresholds (PT), assess reproducibility, and the association with age and parity. STUDY DESIGN: Prospective observational cohort study of healthy women (Canadian task force classification II-2) who underwent QST method of limits at the vagina and introitus for sensation of first awareness and stretch using a modified anorectal physiology protocol. RESULTS: Forty women underwent repeatability testing. Intra- and inter-rater repeatability using intraclass correlation coefficients (ICC) was good to excellent for both first awareness and stretch at the vagina and introitus (intra-rater ICC = 0.93, 0.95, 0.81, and 0.88, respectively; inter-rater ICC = 0.83, 0.93, 0.71, and 0.86 respectively). Normative data were collected from 100 women. Log-linear regression found a significant association between age and PT for first awareness and stretch at the vagina and introitus (P = .020, .008, .002, and <.001, respectively). There was no association with parity and PT. Nomograms were calculated using the 95% confidence limits around the regression line. CONCLUSIONS: Stretch QST is clinically feasible, valid, and reproducible. The test can be used as a tool to measure sensation in women presenting with symptoms of vaginal laxity.