Cultural differences in functional status measurement: analyses of person fit according to the Rasch model

For many reasons it is preferable to use established health related outcome instruments. The validity of an instrument, however, can be affected when used in another culture or language other than what it was originally developed. In this paper, the outcome on functional status measurement using a preliminary version of the Dutch translated 'Pediatric Evaluation of Disability Inventory' (PEDI) was studied involving a sample of 20 non-disabled Dutch children and American peers, to see if a cross-cultural validation procedure is needed before using the instrument in the Netherlands. The Rasch model was used to analyse the Dutch data. Score profiles were not found to be compatible with the score profiles of American children. In particular, ten items were scored differently with strong indications that these were based on inter-cultural differences. Based on our study, it is argued that cross-cultural validation of the PEDI is necessary before using the instrument in the Netherlands.