The Multiple Sclerosis Impact Profile (MSIP). Development and testing psychometric properties of an ICF-based health measure

Purpose. The aim of this study was to develop and test the structure of the Multiple Sclerosis Impact Profile (MSIP), and to evaluate its reliability and validity within a large group of MS patients. Method. Data were obtained from a postal survey of 377 patients attending the Groningen MS centre of the university hospital and 153 patients from the MS patients' association. Results. Factor analysis showed that the MSIP comprised domains representing the four components of the International Classification (ICF). The body functions component comprised two factors, which we divided into three scales: 'muscles and muscle movement functions' (MMF), 'excretion and reproductive functions' (ERF) and 'mental functions' (MF). The activities component comprised one factor, which we divided into two scales: 'basic movement functions' (BMF) and 'activities of daily living' (ADL). The participation component comprised one factor: 'participation in life situations' (PLS). The environmental factors component comprised one factor: 'environmental factors' (EF). Four clinically relevant,symptom' items were added to the questionnaire as single items. The MISP scales yielded sufficient to good internal consistency coefficients. Analysis of the convergent, divergent and known-groups validity indicated that the MSIP measures the physical, psychological and social impact of MS and discriminates between categories of course of disease and disease severity. Conclusion. The MSIP seems to be a reliable and valid ICF-based outcome measure that covers a broad range of clinically relevant aspects of health. ICF can play an important role in measurement development and improvement of a unified and standard language in clinical practice and research.