Use of SF-36 and SF-12 health status measures - A quantitative comparison for groups versus individual patients

BACKGROUND. The extent to which SF-12 scores reflect SF-36 scores has not b een well studied. OBJECTIVES. One purpose was to compare the sensitivity to change of the SF- 36 Physical Function sub-score, and the Physical Component Summary Scores ( PCS) of the SF-36 and SF-12 on patients with low back pain (LBP). A second purpose was to determine if the SF-12 could serve as a surrogate measure fo r the SF-36 when making decisions about individual patients. SUBJECTS. The sample consisted of 101 consecutive patients. MEASURES. SF-36 questionnaires were completed by patients at both initial a nd discharge examinations. SF-12 scores were calculated from the completed SF-36 questionnaires. Therapists' judgments of whether patients were judged to have returned to premorbid function served as the construct for meaning ful clinical change. ANALYSIS. Receiver Operating Characteristic (ROC) curve analysis and repeat ed measures MANCOVA were used to assess sensitivity to change. Linear regre ssion and 95% prediction bands described the extent to which SF-12 scores p redict individual SF-36 scores. RESULTS. No significant differences were found between the ROC curve areas for the Physical Function sub-scale, the PCS-36 and PCS-12. No significant differences were found for the comparison of change scores between PF-36, P CS-36 and PCS-12 scores. CONCLUSION. The findings suggest that Physical Function sub-scores, SF-36 a nd SF-12 PCS scores are equally sensitive to change. SF-12 PCS scores do no t adequately predict SF-36 PCS scores for individual patients. The PCS-12 s hould probably not be used to make judgments about the health status of ind ividual patients with LBP.