Refinement of the questionnaire 'quality of care from the patient's perspective' using structural equation modelling

In 1994, the questionnaire 'Quality of Care from the Patient's Perspective' (QPP) was developed using a conventional factor analytical approach (Wilde et al. 1994). The items and conceptual framework of this questionnaire were derived from a theoretical model, which, in turn, was developed from qualitative patient interviews, using a grounded theory method of analysis (Wilde et al. 1993). The aims of this study were to develop further the dimensionality of the QPP using structural equation modelling combined with advances in factor analysis modelling, and to refine the instrument. This comparatively new methodology extracts more information out of questionnaire data and is considered to be superior to traditional scaling methods. The sample consisted of 611 somatic inpatients from four departments at a Swedish hospital. Data collected with the QPP were explored with the new tool tracing the dimensions postulated in the theoretical model underlying the QPP. A nested factor model was developed fulfilling statistical criteria for adjustment between model and data. The model consists of a general factor and 16 subordinate factors. Most of the original QPP scales were reproduced with the new statistical technique. However, some content changes were made which appear to bring the QPP scales closer to patients' meaning representations of the area. Some changes were also made to the response format, changes which appear to strengthen the psychometric properties of the instrument. The refined QPP will hopefully contribute to a more differentiated picture of quality of care when applied in the field. All scales, items, and response formats of the revised QPP are presented in an appendix.