Research

Validity of SF-12 summary scores in a Greek general population

Nick Kontodimopoulos¹ , Evelina Pappa¹ , Dimitris Niakas¹ and Yannis Tountas^1,2

¹  Hellenic Open University, Faculty of Social Sciences, Riga Fereou 169 & Tsamadou, Patras 26222, Greece

²  Center for Health Services Research, Department of Hygiene and Epidemiology, Medical School, University of Athens, 25 Alexandroupoleos St., Athens 11527, Greece

author email corresponding author email

Health and Quality of Life Outcomes 2007, 5:55doi:10.1186/1477-7525-5-55

Published:	28 September 2007

Abstract

Background

The 12-item Health Survey (SF-12) was developed as a shorter alternative to the SF-36 for use in large-scale studies, particularly when overall physical and mental health are the outcomes of interest instead of the typical eight-scale profile. The main purpose of this study was to assess the validity of the Greek version of the SF-12.

Methods

A stratified representative sample (N = 1005) of the Greek general population was interviewed. The survey included the SF-36, the EQ-5D and questions on socio-demographic and health-related characteristics. SF-12 summary scores were derived using the standard US algorithm. Factor analysis was used to confirm the hypothesized component structure of the SF-12 items. Construct validity was investigated with "known groups" validity testing and via convergent and divergent validity, which in turn were assessed by the correlations with the EQ-5D dimensions. Concurrent validity was assessed by comparisons with SF-36 summary scores.

Results

SF-12 summary scores distinguished well, and in the expected manner, between groups of respondents on the basis of gender, age, education, socio-economic status, self-reported health problems and health services utilization, thus providing evidence of construct validity. Effect size differences between SF-36 and SF-12 summary scores were generally small (<0.2), supporting concurrent (criterion) validity. Significantly lower mean PCS-12 and MCS-12 scores were observed for respondents reporting chronic conditions compared to those without (P < 0.001). Convergent and divergent validity were supported by expected relationships with the EQ-5D. Reporting a problem in an EQ dimension was associated with lower SF-12 summary scores, supporting concurrent validity. Sensitivity of the Greek SF-12 and replication of the original measurement and conceptual model were demonstrated.

Conclusion

The results provide evidence on the validity of the Greek SF-12 and, in conjunction to future studies addressing test-retest reliability and responsiveness, support its use in Greek health status studies as a brief, yet valid, alternative to the SF-36.