Assessment of reproducibility and unidimensionality of international prostate symptom score Japanese version

Abstract

(Background) International Prostate Symptom Score (IPSS) which is a self-administered questionnaire consisting of 7 questions with 6 categories, has been used in many countries as the standard scale of subjective urinary symptoms of patients with prostatism. In Japan, although we have already used the Japanese version at daily clinical situations the reproducibility and validity of it have never been examined. We tried to assess the reproducibility and unidimensionality of the questionnaire. (Patients and Methods) 64 out-patients with benign prostatic hyperplasia were asked to fill the self-administered questionnaires, first at the hospital, and second at home. (Results) The weighted kappa statistics were low in almost all the items (0.10~0.75), so the reproducibility was evaluated to be poor. For as reasons, it was suggested that understandings of Japanese translation and recognition of frequency about chronic urinary symptoms were difficult for the respondents. The results of principal component analysis showed that the item for nocturia measures a different aspect from what the other items measured. So the unidimensionality of the scale was also not confirmed. (Conclusion) These results suggested that IPSS Japanese version should be further modified, especially on its Japanese translation, and then the unidimensionality should be examined again.