Construct and criterion validity of the SF-12 health questionnaire in patients with acute myocardial infarction and unstable angina.
BACKGROUND
The aim of the study was to determine the construct and criterion validity of the 12-item short-form questionnaire (SF-12) in coronary patients with either acute myocardial infarction or unstable angina in Spain.


METHOD
A total of 186 patients hospitalized with coronary heart disease have been studied. The construct validity has been analysed by means of the association between the SF-12v.1 and sociodemographic and clinical variables; and the criterion validity was tested by the correlations between 36-item short-form question (SF-36) and SF-12 summary scores. The equivalence between both health questionnaires was examined by means of the proportion of variance in the SF-36 physical and mental component summary (PCS-36 and MCS-36) scores explained by the 12 items adjusted by age and sex.


RESULTS
The validation result was as expected: female patients and those with poor education level, worse mental health, unstable angina, cardiovascular risk factor and co-morbidity obtained a lower score in the SF-12. The correlations between SF-36 and SF-12 summary scores were high. The equivalence between the SF-12 and SF-36 was good, because the models explained 87% of the variation in PCS-36 score and 93% of the variation in MCS-36.


CONCLUSION
The SF-12 is a valid tool in studies assessing health-related quality of life in coronary patients. The use of the SF-12 may be especially useful in patients where the clinical situation make difficult the application of the longer instrument.