Psychometric evaluation and establishing norms of Croatian SF-36 health survey: framework for subjective health research

Abstract

Aim: To provide population norms and evaluate metric characteristics of the Croatian version of SF-36 Health Survey, an internationally used instrument for assessing subjective health.

Method: The questionnaire was administered to a representative sample of Croatian adult population (n=9070). Three standard techniques were used in data analysis: reliability tests, descriptive statistics, and factor analysis. The population norms were presented in two standard forms--the SF-36 Health Profile and percentile values for different age groups of men and women.

Results: The Croatian version of the SF-36 had generally acceptable metric characteristics including its construct validity. The internal consistency of the SF-36 scales ranged from 0.78 to 0.94. Pearson bivariate correlations showed moderate associations between SF-36 scales, and factor analysis provided one latent dimension underlying all SF-36 scales which explained 63.3% of the score variance. Less favorable results were obtained concerning its discriminative validity. All SF-36 scales showed negative asymmetry of score distributions, and some had high floor and ceiling effects--skewness estimations ranged from -0.12 to -0.91, with the highest floor effect of 30% and ceiling effect of 63%.

Conclusion: Presented population norms for the Croatian version of SF-36 Health Survey showed that SF-36 may be used as a valid and reliable instrument in research in subjective health of Croatian population.

Figures

Figure 1

SF-36 Health Profile obtained on representative samples of Croatian (n = 9070; in 2003) and US (n = 2474; in 1990) adult population. Scores are scale mean values for men and women. PF – physical health; RP – role physical; BP – bodily pain; GH – general health; VT – vitality; SF – social functioning; RE – role emotional; MH – mental health; full lines – profile of Croatian norms; doted lines – profile of US norms.

Figure 2

SF-36 Health Profile obtained on a representative sample of general adult population (n = 9070) οϕ Χροατια ιν 2003: Ωϵιγητϵδ−σχαλϵ μϵαν ϖαλυϵσ ϕορ γϵνϵραλ ποπυλατιον ανδ διϕϕϵρϵντ αγϵ γρουπσ οϕ μϵν ανδ ωομϵν. ΠΦ □ πηψσιχαλ ηϵαλτη; ΡΠ □ ρολϵ πηψσιχαλ; ΒΠ □ βοδιλψ παιν; ΓΗ □ γϵνϵραλ ηϵαλτη; ςΤ □ ϖιταλιτψ; ΣΦ □ σοχιαλ ϕυνχτιονινγ; ΡΕ □ ρολϵ ϵμοτιοναλ; ΜΗ □ μϵνταλ ηϵαλτη; διαμονδ □ ποπυλατιον προϕιλϵ; σθυαρϵ □ προϕιλϵ ϕορ 18−24−ψϵαρ αγϵ γρουπ; τριανγλϵ □ προϕιλϵ ϕορ 25−34−ψϵαρ αγϵ γρουπ; χροσσ □ προϕιλϵ ϕορ 35−44−ψϵαρ αγϵ γρουπ; σταρ □ προϕιλϵ ϕορ 45−54− ψϵαρ αγϵ γρουπ; χιρχλϵ □ 55−64−ψϵαρ αγϵ γρουπ; μυλτιπλιχατιον σιγν □ προϕιλϵ ϕορ ≥65-year age group.

Figure 3

SF-36 Reported Health Transition according to the population age and sex (n = 9070) in Croatia in 2003. Vertically-lined bars – much better; open bars – somewhat better; diagonally-lined bars – same; horizontally-lined bars – somewhat worse; closed bars – much worse.