THE EQUIVALENCE OF SF-36 SUMMARY HEALTH SCORES ESTIMATED USING STANDARD AND COUNTRY-SPECIFIC ALGORITHMS IN 10 COUNTRIES - RESULTS FROM THE IQOLA PROJECT

Data from general population surveys (n = 1711 to 9151) in nine Europe an countries (Denmark, France, Germany, Italy, the Netherlands, Norway , Spain, Sweden, and the United Kingdom) were analyzed to test the alg orithms used to score physical and mental component summary measures ( PCS-36/MCS-36) based on the SF-36 Health Survey. Scoring coefficients for principal components were estimated independently in each country using identical methods of factor extraction and orthogonal rotation. PCS-36 and MCS-36 scores were also estimated using standard (U.S.-deri ved) scoring algorithms, and results were compared. Product-moment cor relations between scores estimated from standard and country-specific scoring coefficients were very high (0.98 to 1.00) for both physical a nd mental health components in all countries. As hypothesized for orth ogonal components, correlations between physical and mental components within each country were very low (0.00 to 0.12) for both estimation methods. Mean scores for PCS-36 differed by as much as 3.0 points acro ss countries using standard scoring, and mean scores for MCS-36 differ ed across countries by as much as 6.4 points. In view of the high degr ee of equivalence observed within each country, using standard and cou ntry-specific algorithms, we recommend use of standard scoring algorit hms for purposes of multinational studies involving these 10 countries . (C) 1998 Elsevier Science Inc.