Predicting follow-up functional outcomes in outpatient rehabilitation

Functional outcomes at an average of six months after outpatient rehabilitation were investigated in a pilot study with a sample of 42 patients receiving physical therapy for low back, neck, and other musculoskeletal problems. Logistic regression analyses were used to study variables related to the achievement of a predetermined level of physical functioning or to whether improvement occurred from initial to follow-up assessment. Scales used in the analyses were obtained from two measures of functioning, the Medical Outcomes Trust Short Form 36 (SF-36) and the Medical Rehabilitation Follow Along (MRFA(TM) instrument). Demographic and program characteristics variables obtained from clinic records were also included in the analyses. The independent variables entered into two groups of regression equations included age, gender, presenting problem, workers' compensation coverage, functioning at initial assessment, number of visits, length of program, and intensity of program. For the SF-36, the General Health scale and presenting problem predicted above or below a level greater than one standard deviation less than the mean on the Physical Functioning scale at follow-up. The combination of the Role Physical and Role Emotional scales predicted follow-up level on the Physical Component Summary (PCS) scale. The interaction of age and intensity of treatment was predictive for both the Physical Functioning and PCS scales. For predicting improvement or no improvement using the SF-36 scales, General Health and the interaction between age and intensity were predictive of change on the PhysiCal Functioning scale, whereas age and the interaction between age and number of visits were predictive of change on the PCS scale. For the MRFA(TM) instrument, the interactions between age and the intensity of treatment was predictive for both a predetermined level of physical functioning and amount of improvement in physical functioning at follow-up. An intensity rating of pain and a measure of affective distress at initial assessment both improved the identification of patients at risk for not reaching a given level of functioning whereas treatment intensity improved the identification of those patients at risk for not showing improvement at follow-up. Length of time between the end of outpatient therapy and follow-up assessment was generally not related to follow-up physical functioning. Interpretation and implications of these findings, as well as applications of this analytic approach to outcomes assessment, are discussed.