Test-retest variation of pressure flow parameters in men with bladder outlet obstruction

We assess short-term (5 to 10 minutes) and long-term (24 weeks) test-retest changes of repeated pressure flow examinations.

The pressure flow charts of 84 patients with benign prostatic enlargement and bladder outlet obstruction who had received either androgen suppressive therapy or placebo were reviewed retrospectively. Pressure flow examinations were performed at baseline, and at weeks 24 and 48. Each pressure flow session included 3 sequential voids.

Median detrusor opening pressure, maximum detrusor pressure, detrusor pressure at maximum flow rate and minimum voiding pressure decreased statistically significantly from void 1 to 2, ranging from 9.5% to 15.8%. From void 2 to 3 during the same pressure flow session there was a further reduction in obstruction parameters. Median Abrams/Griffiths number was 10.7% lower at void 2 compared to void 1 (p <0.0001) and the urethral resistance algorithm was 3.2% lower (p <0.0001). Long-term test-retest changes from baseline to week 24 and from week 24 to week 48 for the pressure flow parameters studied were negligible.

Changes in pressure flow parameters at short-term test-retesting are considerable and probably of clinical significance. The standard pressure flow nomograms, which are based on single void pressure flow studies, might need modification when applied to repeat void studies.