PRESSURE-FLOW STUDIES - AN EVALUATION OF WITHIN-TESTING REPRODUCIBILITY - VALIDITY OF THE MEASURED PARAMETERS

The within-examination variation in selected test parameters in repeal ed pressure-flow studies was determined in a retrospective study of co nsecutive pressure-flow examinations in 105 patients. It was further e valuated to see whether then was a systematic change in the measured p arameters during retesting. To see if variation and reproducibility we re influenced by the procedure of investigation, i.e., transurethral o r suprapubic, patients were grouped according to the method employed. Finally, the effect of detrusor instability on the measurements was ev aluated. Using the Abrams-Griffiths nomogram, patients were classified as obstructed, equivocal, or unobstructed. The test-retest variations in classification were evaluated. We found a systematic variation in P-det.Qmax, P-det.Open, and Q(max) during testing, indicating a physio logical effect of repeated pressure-flow studies resulting in a less o bstructed second voiding. Accordingly, 69% of the patients who shifted group of classification during retesting shifted to a group of lesser obstruction at the second voiding. Still, 88% of patients remained in the same group of classification of bladder outlet obstruction. Withi n- and between-patient variations and reproducibility of the test resu lts were not influenced by the procedure of investigation, i.e., the t ransurethral or suprapubic method. However, we found variations sugges ting a decrease in urethral resistance and bladder contractility from test to test in the transurethral group, whereas variations suggesting an isolated decrease in bladder contractility were seen in the suprap ubic group. Detrusor instability per se does not seem to cause any sys tematic changes during repeated testing. (C) 1997 Wiley-Liss, Inc.