[Interpretation of SF-36 and SF-12 questionnaires in Spain: physical and mental components].
OBJECTIVE
The SF-36 is one of the most widely evaluated and used quality of life questionnaires. Two summary components (physical and mental) have been developed from its 8 original dimensions. The objective of this study was to obtain the Spanish weights to calculate the summary components of the SF-36 and the SF-12, to evaluate their metric characteristics, and to obtain general population based reference norms.


METHODS
Representative samples of the Spanish population gathered from 2 cross-sectional studies: <<Drug consumption home survey>> (n = 9151) and <<Arterial hypertension and other risk factors in the elderly>> (n = 3,004). The Spanish weights of the summary components of SF-36 and SF-12 were calculated by principal component analysis and multiple linear regressions, respectively. Known groups were compared to evaluate construct validity and reliability was assessed with internal consistency coefficients.


RESULTS
The Spanish weights obtained were very similar to those of the original American version (correlation > 0.9). The SF-12 items explained a 91% of the variance of SF-36 summary components. All the scores were lower (worse) in the elderly and most underprivileged groups (p < 0.001). Internal consistency coefficients were close to 0.9 for the SF-36, and slightly lower for the SF-12.


CONCLUSIONS
Physical and mental summary components estimated with Spanish weights are reliable and valid. The Spanish general population based norms of these summaries will facilitate the interpretation of quality of life results assessed with the SF family of questionnaires in Spanish studies.
Vilagut
Gemma
G
Unidad de Investigación en Servicios Sanitarios. Institut Municipal d'Investigació Mèdica. IMIM-Hospital del Mar. Barcelona. España. / CIBER en Epidemiología y Salud Pública (CIBERESP). España.
Valderas
José María
JM
Ferrer
Montserrat
M
Garin
Olatz
O
López-García
Esther
E
Alonso
Jordi
J
D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008603:Mental Health; D008875:Middle Aged; D011788:Quality of Life; D012016:Reference Values; D013030:Spain; D011795:Surveys and Questionnaires