Objectives: Numerous outcomes measures can be used to capture and differentiate change in different constructs comprising recovery. Consequently, patients are often burdened by completing a number of measures which involves considerable time and effort. The purpose of this longitudinal, observational study was to identify the number of dimensions in a battery of self-report findings in a patient population who received shoulder injections to investigate the association of the instruments.
Methods: Ninety-nine subjects, with diagnoses of adhesive capsulitis, labral injuries, rotator cuff injuries, and osteoarthritis completed outcomes measures including five different forms of pain intensity measures, the McGill Short Form Questionnaire, and the Disabilities of the Arm, Shoulder, and Hand Questionnaire. Change scores were calculated at 4 weeks and an exploratory factor analysis (EFA) with varimax rotation was used to analyze dimensionality. The relationship between the raw scores of the seven measures was investigated using a correlation matrix.
Results: The EFA yielded only one factor and the raw score correlations demonstrated very strong, significant associations. The finding of a single factor suggests that in this sample of patients, only one dimension of change, most likely a change in pain, is represented by the seven individual outcomes measures.
Discussion: In this isolated example, one outcomes measure would have been sufficient in determining outcome and could have reduced the administrative burden to the caregivers and the patients.
Keywords: Factor analysis; Outcomes measures; Shoulder.