Pain research & management : the journal of the Canadian Pain Society = journal de la société canadienne pour le traitement de la douleur
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The Multidimensional Pain Inventory (MPI) is a reliable and valid self-report instrument that measures the impact of pain on an individual's life, quality of social support and general activity. Criticism of the MPI has focused on this instrument's internal structure and the stability of its classification taxonomy. ⋯ Based on principal components analysis, three summary scales were developed that reflected level of impairment, social support and activity. Summary scales possessed good psychometric qualities and, when cluster analyzed, replicated the MPI taxonomy. Exploratory analyses of the MPI taxonomy revealed that goodness-of-fit values generally became less reliable as respondent profiles approached the overall sample mean. When the relative distance between respondents fit to taxonomy profiles and the distance from the sample mean was considered, profile stability using summary scales was predicted with good precision. These results suggest that summary scales may enhance the usefulness of the MPI, and that the traditional method of determining profile fit within the MPI is not stable and needs to be reconsidered.