Does uroflowmetry parameter facilitate discrimination between detrusor underactivity and bladder outlet obstruction?

PURPOSE: Though urodynamic study (UDS) is the current established standard to distinguish between detrusor underactivity (DU) and bladder outlet obstruction (BOO), concerns of patient discomfort and potential complications of catheterization deters its use. We inspected clinical variables to discriminate between DU and BOO in uroflowmetry, which can be more easily performed in clinical practice. MATERIALS AND METHODS: Total 240 men who both underwent UDS and uroflowmetry were reviewed. The patients were divided into 2 groups by a single experienced urologist based on UDS outcome; DU (n=111) and BOO (n=129). From uroflowmetry, 5 variables including maximal flow rate (Qmax), average flow rate (Qave), voiding volume (VV), postvoid residual urine (PVR), and value of Qmax minus Qave (DeltaQ) was obtained. Multivariable analysis including receiver operating characteristic (ROC) curve analysis was performed to identify the important diagnostic predictors. RESULTS: The mean age (±standard deviation) was 65.3±9.2 years. Except Qave, all uroflowmetry components were significantly different between DU and BOO groups. DeltaQ was smaller in DU group (8.71 mL/s vs. 5.26 mL/s, p<0.001). By logistic regression analysis, DeltaQ (Exp(B)=0.648, p<0.001) and PVR (Exp(B)=1.009, p<0.001) significantly discriminate DU and BOO diagnosis. In diagnosing DU using a single variable, the area under the curve of ROC from DeltaQ (0.806) was significantly higher than that from Qmax (0.763, p=0.0126) and Qave (0.574, p<0.0001). CONCLUSIONS: Our findings suggest that DeltaQ is a novel predictor capable of discriminating DU from BOO in men with obstructive lower urinary tract symptom.