Validation of the Japanese SF-36 v2 acute form in patients with chronic kidney disease

Objective : The SF-36v2 (version 2 of the SF-36 health survey) is an instrument used worldwide to measure the generic health-related quality of life (HQOL). The SF-36v2 has "standard" and "acute" forms, in which respondents are asked about the previous month and the previous week, respectively. The standard form of the Japanese-language version of the SF-36v2 has already been validated, but the acute form has not. We evaluated the validity and reliability of the Japanese SF-36v2 acute form in patients with chronic kidney disease (CKD). Methods : Cross-sectional data from 210 CKD patients who enrolled a clinical trial of a long-acting erythropoiesis stimulating agent (darbepoetin alfa) were analyzed. The feasibility of question items and distributions of the response choices were examined. Cronbach's alpha was computed to assess internal-consistency reliability. Construct validity was evaluated with tests of convergent and discriminant validity, and with factor analysis. Validity with regard to reference groups for the severity of anemia and for performance states was also assessed. Results : There were few missing data and the distribution of response choices did not differ between the acute form and the standard form. Values of Cronbach's alpha for the acute form sub-scales were sufficient. The percentages of items that passed the tests of convergent validity and discriminant validity were 100 % and 98.7 %, respectively. Factor analysis identified the same components in the acute form as in the standard form. "Dose-response" relationships were found between the sub-scale scores on the acute form and the severity of anemia, and also between those scores and performance states. Conclusions : The Japanese SF-36v2 acute form can be expected to provide valid and reliable HQOL data in CKD patients.