Intrasubject variability of the pressure-transmission ratio in patients with genuine stress incontinence.

The aim of the study was to determine the intrasubject variability of the pressure-transmission ratio (PTR) with various cough intensities in subjects with genuine stress incontinence. Thirty-six patients with genuine stress incontinence underwent multichannel urodynamics and had a series of pressure-transmission ratios (PTRs) determined with the urethral transducer placed at the point of the maximal closure pressure. Patients were asked to cough with increasing intensities and three to four different cough-induced PTRs were recorded for each subject. The data were analysed using regression analysis, repeated measures analysis of variance and comparison of variance. The PTRs showed a high degree of variability within subjects. The mean within subject standard deviation was 18.5%. The effect of parity, maximal urethral closure pressure and age were insignificant on the variability. Cough intensities of greater than 90 cmH2O have a lesser degree of variability. The mean PTR across all cough intensities was fairly constant in the 82%-87% range. It was concluded that the PTR in an individual has a high degree of variability independent of cough intensity, and cannot be relied upon as a diagnostic measure in subjects with genuine stress incontinence. However, the PTR for the population as a whole was consistent across all cough intensities.