A comparison of perineometer to brink score for assessment of pelvic floor muscle strength

Abstract

Objective: The Brink scale is a commonly used digital assessment of pelvic floor muscle strength. The Peritron perineometer, a compressible vaginal insert that records pressure in centimeters of water, offers an objective method for this evaluation. This study evaluates the inter- and intrarater reliability of perineometry measurements and correlates those values with Brink scores.

Study design: Subjects were prospectively enrolled and underwent pelvic floor muscle strength assessment by 2 examiners each using a perineometer and the Brink scale. Perineometer measurements of maximum pressure, average pressure, and total duration were recorded for 3 consecutive pelvic floor muscle contractions (Kegels). The Brink assessment was performed by placing 2 fingers vaginally during a single Kegel contraction. Brink scores consisted of 3 separate 4-point rating scales for pressure, vertical finger displacement, and duration. The order of the examiners and the 2 assessment methods were randomized, and each examiner was blinded to the results of the other. Pearson and Spearman correlation coefficients were used for analysis as appropriate. Repeated-measures analysis of variance was used to assess intrarater reliability between repeated perineometer measurements.

Results: One hundred women were consecutively enrolled and completed the study. Interrater reliability for the perineometer maximum squeeze pressure (r = 0.88) and baseline resting pressure (r = 0.78) was high. Maximum squeeze pressure correlation was unaffected by the presence or absence of estrogen (r = 0.89 versus r = 0.85), nulliparity versus parity (0.85 versus 0.88), or genital hiatus 4 or greater or less than 4 (r = 0.96 versus r = 0.86). Total Brink score and each individual submeasurement showed good correlations (total: r = 0.68; pressure: r = 0.68; displacement: r = 0.58; duration: r = 0.44). The correlation between maximum squeeze pressure and total Brink score during the first and second exams was good (r = 0.68 versus r = 0.71). For intrarater reliability, there were no significant differences among the 3 maximum squeeze pressures recorded during the first exam (P = .11), but for the second exam, the first squeeze was significantly stronger than the successive 2 (P = .009) attempts.

Conclusion: Perineometer measurements of pelvic floor muscle contractions show very good inter- and intrarater reliability. The Brink total and pressure scores had a slightly lower interrater reliability. Variables such as estrogen status, parity, and genital hiatus did not appear to affect correlation. There was good correlation between the maximum perineometer pressure and the total Brink score, suggesting that these 2 methods of assessment have similar levels of reproducibility. Additionally, the perineometer demonstrated good short-term test-retest reliability.