THE DAY-TO-DAY VARIATION (TEST-RETEST RELIABILITY) OF RESIDUAL URINE MEASUREMENT

Objective To determine the variation measurements of post-void residua l (PVR), determined by transabdominal ultrasonography (TAUS), within a n individual over time (test-retest reliability), Patients and methods Forty men with symptomatic benign prostatic hyperplasia and awaiting transurethral resection of the prostate were studied over 3 months. Ea ch underwent TAUS to determine both pre-and post-micturition residual volumes on six occasions within the study period. Results Although one -third of the patients had approximately constant residual volumes (va riation in range <120 mL), two-thirds had wide intra-individual variat ions over time (variation in range 150-670 mL). The values were log tr ansformed to give a normal distribution and subjected to analysis of v ariance; there was a wide variation between and also within individual s, The larger the mean PVR, the larger was the overall variation in ti me. For those with a mean PVR of <100 mL, the variation was less marke d and these patients showed a more consistent test-retest repeatabilit y. Conclusions Although the PVR determined by TAUS may be useful to in dicate aspects of bladder dysfunction or outlet obstruction, the wide variation in repeated measurements in the same individual limits its u se for any clinical purpose that requires repeated assessment, e.g. in monitoring the response to treatment. There is poor test-retest relia bility and PVRs cannot be determined reliably from a single measuremen t.