Evaluation of psychometric properties of Japanese version of International Prostate Symptom Score and BPH Impact Index

(Purpose) To evaluate psychometric properties of the Japanese version of International Prostate Symptom Score (IPSS) and BPH Impact Index (BII), (Methods) The translated IPSS and BII questionnaires were administered to 103 patients with benign prostatic hyperplasia and 23 asymptomatic men. In 82 patients the questionnaires were repeated 2 weeks later to examine reproducibility. Further 2 weeks later 21 out of 82 patients responded to the questionnaires asking symptoms during the last week rather than during the last month. To evaluated responsiveness the questionnaires were repeated after treatment in 22 patients. Internal consistency, construct validity and criterion validity were examined by proper statistic methods. (Results) Reproducibility was good to excellent with weighted kappa more than 0.62 for all items. It was not significantly affected by age, symptom severity, institution type, or whether the patients were asked symptoms during the last week or during the last month. Internal consistency was also good with Cronbach's α more than 0.83. Principle component analysis identified 2 components in IPSS and a single component in BII, with all the items contributing to the first component. Most items had significant correlation with external criteria including maximum flow rate, residual urine volume or prostate volume. The scores of patients were clearly larger than asymptomatic men and obviously reduced after receiving therapies, (Conclusion) Japanese translations of IPSS and BII were shown to be reliable, valid and one-dimensional instruments in the Japanese patients. They would be equivalent to the original English questionnaires.