[A comparative analysis of SF-12 with the SF-36 among patients in methadone treatment]

The concordance of the physical and mental component summary scores of the Short Form (SF)-36 has been established using the SF-12 in general and selected patient populations but has yet to be assessed in patients with drug addiction.

To investigate whether a shorter health status instrument, the short form (SF)-12, is comparable with its longer version, the SF-36, for measuring health-related quality of life of patients with addictive disorders in treatment with methadone.

A cross-sectional study was carried out on a stratified random sample (n= 726) of users included in the Methadone Maintenance Programmes in the Basque Country in Spain. The SF-36 Health Survey was used and the physical component summary (PCS) and mental component summary (MCS) of the SF-36 and SF-12 were calculated. Intraclass correlation coefficients (ICCs) and linear regression were used to assess the ability of the SF-12 physical component summary (PCS-12) scores to predict PCS-36 scores and the SF-12 mental component summary (MCS-12) scores to predict MCS-36 scores.

The concordance between the SF-12 and the SF-36 on both physical (ICC = 0.97) and mental (ICC = 0.98) component summary scores (PCS and MCS respectively) is high and the relationship is linear and positive. Most of the variance in the SF-36 PCS (R2 = 0.88) and MCS (R2 = 0.91) can be explained by their SF-12 counterparts.

The SF-12 reproduced SF-36 summary scores without substantial loss of information when used on patients undergoing methadone treatment. The SF-12 appears to be an efficient alternative to the SF-36 for the assessment of health-related quality of life of patients with addictive disorders and their treatment.