A shorter form health survey: can the SF-12 replicate results from the SF-36 in longitudinal studies?

BACKGROUND: The SF-36 is a generic health status measure which has gained popularity as a measure of outcome in a wide variety of patient groups and social surveys. However, there is a need for even shorter measures, which reduce respondent burden. The developers of the SF-36 have consequently suggested that a 12-item sub-set of the items may accurately reproduce the two summary component scores which can be derived from the SF-36 the Physical Component Summary Score (PCS) and Mental Health Component Summary Score (MCS). In this paper, we adopt scoring algorithms for the UK SF-36 and SF-12 summary scores to evaluate the picture of change gained in various treatment groups. METHODS: The SF-36 was administered in three treatment groups (ACE inhibitors for congestive heart failure, continuous positive airways therapy for sleep apnoea, and open vs laparoscopic surgery for inguinal hernia). RESULTS: PCS and MCS scores calculated from the SF-36 or a sub-set of 12 items (the 'SF-12') were virtually identical, and indicated the same magnitude of ill-health and degree of change over time. CONCLUSION: The results suggest that where two summary scores of health status are adequate than the SF-12 may be the instrument of choice.