Factor structure of the Multnomah Community Ability Scale--longitudinal analysis.

Community mental health services benefit from measuring clinical outcomes relevant to a community-based context in contrast to medically modeled outcomes. The Multnomah Community Ability Scale (MCAS) addresses broad dimensions of community functioning and was developed for clinical and evaluation purposes. We assessed the structural consistency and fit of the scale as a measure of community functioning through confirmatory factor analysis using a longitudinal sample of individuals (n=408) with severe and persistent mental illness receiving services from community mental health programs. None of the previously hypothesised factor solutions achieved a good fit and a high degree of invariance over time was observed. Through exploratory factor analysis, the possibility of alternative solutions was explored. After exclusion of two of the 17 items, four models--including four-, three-, two- and one-factor solutions--were tested for fit and invariance with no improvement. We discuss our findings of poor fit under the assumption that the MCAS should psychometrically behave as a scale. Alternative interpretations for the tool and suggestions for the use of its items as an index that measures aspects of disability are proposed.