Comparison of three methods of quantifying urethral resistance in men

To determine how well three methods of quantifying urethral resistance from pressure-flow plots compared in men.

The pressure-flow plots of 312 men who attended a Continence Clinic for evaluation of lower urinary tract symptoms were analyzed. The Abrams-Griffiths number (AG), detrusor-adjusted mean PURR [passive urethral resistance relation] factor (DAMPF), and group-specific urethral resistance factor (URA) were obtained for each plot. The correlation coefficients and simple regression equations were computed for AG versus DAMPF and AG versus URA. Using the provisional International Continence Society method for definition of obstruction to categorize the AG values as obstructed, equivocal, or unobstructed, we obtained the corresponding DAMPF and URA values for our study population.

The Pearson correlation coefficient, r, for AG versus DAMPF and AG versus URA was 0.941 and 0.889, respectively. The corresponding regression equations obtained were AG = - 32.6 + (DAMPF)1.27 (95% confidence interval [CI] 1.22 to 1.32) and AG = - 16.4 + (URA) 1.67 (95% CI 1.58 to 1.77). The 5th to 95th percentiles of the DAMPF and URA for men who were obstructed (AG number more than 40) were 56 to 92 and 28 to 71, those for men who were equivocal (AG 20 to 40) were 35 to 62 and 17 to 38, and those for men who were unobstructed (AG less than 20) were 12 to 44 and 5 to 24, respectively.

The DAMPF and URA were highly correlated to the AG in a linear fashion. Although these parameters were developed differently, they appeared to compare well. When using the DAMPF or URA to quantify urethral resistance, it was possible to estimate the corresponding AG value with reasonable confidence.