Measuring participation when combining subjective and objective variables : the development of the Ghent Participation Scale (GPS)

BACKGROUND: The ICF reflects a bio-psycho-social paradigm and is increasingly used in outpatients rehabilitation settings. The component of participation is in the 1CP the manifestation of a bio-psycho-social reasoning. Different participation measures have already been developed and were operationalized through objective and/or a limited set of subjective variables, but keeping them as separate concepts. There is still need for a generic participation instrument including both objective and all relevant subjective variables resulting in one participation score. AIM: To develop a generic participation measure based on objective and subjective aspects and leading to one final score; the Ghent Participation Scale (GPS). Additionally it was the aim to explore whether the GPS has a good internal validity by means of factorial validity and homogeneity and whether the GPS is feasible and interpretable. DESIGN: Cross-sectional study. SETTING: Outpatient rehabilitation centre. POPULATION: One hundred thirty former rehabilitation outpatients with various conditions. METHODS: Item derivation for the GPS was based on qualitative research. The participants administered the GPS in the third week after discharge from the Ghent University Hospital. An exploratory factor analysis was performed to determine underlying dimensions. Statistical coherence was expressed in both item -total correlations and in Cronbach's a coefficient. RESULTS: An exploratory factor analysis showed 3 underlying dimensions within the GPS: I) performing activities according to preferred choices and wishes; 2) social appreciation and acceptance by performing activities; and 3) the need to delegate activities explaining 55.8% of the total variance. The results show a good to strong homogeneity (item -total ranged from 0.58 to 0.80) and a strong internal consistency (Cronbach's a ranged from 0.76-0.92). CONCLUSIONS: The results of this preliminary validation study suggest that the GPS appears to be a valid measure to rate participation. CLINICAL REHABILITATION IMPACT: Further research and more and more powerful psychometric models such as Rash Analysis or Item Response models are needed to establish a psychometrically sound instrument