[Estimating utility values for health status using the Spanish version of the SF-36. Validity of the SF-6D index vs EQ-5D].

BACKGROUND AND OBJECTIVE

A new utility index derived of the SF-36, the SF-6D, was recently developed and has been compared with other utility measures. The objective was to validate this index in the Spanish version of SF-36 with respect to the EQ-5D.

METHOD

1,843 complete measures of the SF-36 and the EQ-5D from 1,283 patients who received a solid organ transplant were collected. SF-6D values were calculated using the model proposed by its creator and without tariff values (not weighted). EQ-5D values were calculated using Spanish visual analog scale tariff (VAS-t), the time-trade off tariff (TTO-t) and also without tariff values (not weighted). Spearman correlation coefficients were calculated between SF-6D and EQ-5D values.

RESULTS

Mean value (standard deviation) of SF-6D was 0.67 (0.15), of VAS-t, 0.69 (0.24) and of TTO-t, 0.70 (0.32). SF-6D values had moderate correlation with VAS-t (r = 0.734) and TTO-t (r = 0.731) (both p < 0.001). The not weighted SF-6D had a high correlation with the weighted version (r = 0.969, p < 0.001), and moderate with the VAS-t (r = 0.754), TTO-t (r = 0.750) and no weighted EQ-5D (r = 0.784) (p < 0.001).

CONCLUSIONS

The SF-6D index derived from the Spanish version of SF-36 seem to be a valid utility index to be used with the SF-36 databases from studies made in Spain.