Validation of the Japanese version of the Rome II modular questionnaire and irritable bowel syndrome severity index

Background. Instruments for measuring the presence and severity of specific irritable bowel syndrome (IBS) symptoms, comparable to those used in Western countries, have been lacking in Japan. The aim of this study was to develop, validate, and confirm the reliability of the Japanese version of the Rome II modular questionnaire for IBS (RIIMQ-J) and the IBS severity index (IBSSI-J). Methods. Forty-nine patients in the university hospital with chronic or recurrent abdominal pain and discomfort and/or altered bowel habits were enrolled. With Rome II criteria, 27 patients were diagnosed as having IBS, and the other 22 patients were evaluated as having other functional bowel disorders (FBDs). The English versions of RIIMQ and IBSSI were translated into Japanese. After back-translation and approval of the questionnaire, subjects completed both questionnaires twice within 14 days. Results. Cronbach's alpha of the RIIMQ-J was high (0.72). The sensitivity of RIIMQ-J for the diagnosis of IBS was also high (89%). The specificity of RIIMQ-J for denial of IBS among patients with other FBD was satisfactory (73%). The IBSSI-J showed high internal consistency (0.69) and reproducibility (intraclass correlation coefficient, 0.86, P < 0.001). Conclusions. The RIIMQ-J and IBSSI-J are valid, reliable, and appropriate instruments for detecting and assessing the severity of IBS status in Japanese patients.