Are urine flow-volume nomograms developed on Caucasian men optimally applicable for Indian men? Need for appraisal of flow-volume relations in local population

INTRODUCTION: Flow-volume nomograms and volume-corrected flow-rates (cQ) are tools to correct uroflow rates (Q) with varied voided volumes (VV) of urine. We investigated the applicability of the available nomograms in our local population. MATERIALS AND METHODS: Raw data of our previous study on variation in Q with voiding position (standing, sitting, and squatting) in healthy adult men was reanalyzed. Additionally, the departmental urodynamic database of the last four years was searched for uroflow data of men with voiding symptoms (International Prostatic Symptom Score (IPSS) > 7 and global quality of life score >2). These results were projected on the Liverpool and Siroky nomograms for men. The Q-VV relations were statistically analyzed using curve-estimation regression method to examine the current definition of corrected maximum flow rate (Qmax). RESULTS: We found a cubic relation between Q and VV; based on this we developed novel equation for cQ [cQ=Q/(VV)(1/3)] and novel confidence-limit flow-volume nomograms. The imaginary 16(th) percentile line of Liverpool nomogram, -1 standard-deviation line of Siroky nomogram and lower 68% confidence-limit line of our nomogram had sensitivity of 96.2%, 100% and 89.3%, and specificity of 75.3% 69.3% and 86.0%, respectively for Qmax-VV relations. Corresponding values for average flow rate (Qave)-volume relations were 96.2%, 100% and 94.6%, and 75.2%, 50.4% and 86.0%, respectively. The area under curve of the receiver operating characteristics (ROC) curve for cQmax and cQave was 0.954 and 0.965, respectively, suggesting significantly higher discriminatory power than chance (P = 0.0001). CONCLUSION: Flow-volume nomograms developed on Caucasian population may not be optimally applicable to the Indian population. We introduce flow-volume nomograms and cQ, which have high sensitivity and specificity.