Validation testing of a three-component model of Short Form-36 scores.
OBJECTIVE
The two-component factor structure underlying Short Form-36 (SF-36) summary scores may not be valid worldwide. We studied a three-component model of SF-36 scores in Japan.


METHODS
The SF-36 scores came from representative samples of the population of Japan. Factor analysis and structural equation modeling were used. The two-component model gave physical component summary (PCS) scores and mental component summary (MCS) scores. The three-component model gave scores on the PCS, the MCS, and also on the third component, which we call the role component summary (RCS) score. These were evaluated with external criteria.


RESULTS
In the three-component model, the RCS was strongly associated with the role-physical, social functioning, and role-emotional subscales, whereas the PCS and MCS were associated with the physical functioning and mental health subscales, as expected. The goodness-of-fit index was 0.945 for the three-component model and 0.935 for the two-component model. The PCS discriminated between groups stratified by comorbid conditions, and the MCS discriminated between groups stratified by psychological depression. Absence from work was associated with both PCS and RCS.


CONCLUSIONS
The three-component model is better than the two-component model, and it provides more useful PCS and MCS scores. Criteria for validation testing of the RCS are needed.
Suzukamo
Yoshimi
Y
Institute for Health Outcomes and Process Evaluation Research, Kyoto and Tokyo, Japan. suzukamo@med.tohoku.ac.jp
Fukuhara
Shunichi
S
Green
Joseph
J
Kosinski
Mark
M
Gandek
Barbara
B
Ware
John E
JE
D002986:Clinical Trials as Topic; D005163:Factor Analysis, Statistical; D006801:Humans; D007564:Japan; D011594:Psychometrics; D011788:Quality of Life; D011795:Surveys and Questionnaires / Q000592:standards*