Development and initial validation of the back pain functional scale

Study Design. A prospective repeated-measures design was applied. Objectives. To examine the measurement properties of the Back Pain Function al Scale (BPFS) and the Roland-Morris Questionnaire (RMO) and to formulate hypotheses and sample size estimates for a subsequent comparison study. Summary of Background Data. Although there are numerous functional status m easures for patients with low,back. pain, most have been conceived of and v alidated with a group rather than an individual patient as the unit of inte rest. Also, little has been done to formally compare-this includes the gene ration of a priori hypotheses, followed by statistical hypotheses testing-t he many competing measures. Methods. Subjects were 77 patients with low back pain who were referred by physicians to 10 outpatient physical therapy clinics located in Canada and the United States. The questionnaires were administered at patients' initia l visits, within 48 hours of the initial visit, and at 1-, 2-, and 3-week f ollow-up visits. Reliability, cross-sectional validity, and longitudinal va lidity (sensitivity to change) coefficients were calculated. Results. Test-retest reliability estimates of 0.81 and 0.88 were obtained f or the RMO and BPFS, respectively. The measures demonstrated similar levels of cross-sectional validity Correlations of 0.56 and 0.65 were noted betwe en a prognostic rating of change and the RMO and BPFS, respectively. The RM O demonstrated a ceiling effect. Approximately 180 patients are needed for a subsequent head-to-head comparison study of the measures. Conclusions. The BPFS appears to have sound measurement properties, and a f ormal head-to-head comparison study with the RMO is warranted.