Interrater reliability of judgments of the centralization phenomenon and status change during movement testing in patients with low back pain

Objective: To determine the interrater reliability of judgments of status change, including the centralization phenomenon during examination of the lumbar spine, and to determine the effects of training and experience on reliability. Design: A videotape study of judgments by physical therapists and physical therapy students of the results of movement testing during the examination of patients with low back pain. Setting: Outpatient physical therapy clinic. Patients: Patients receiving physical therapy treatment for low back pain. Intervention: Patients with low back pain were videotaped while performing a variety of movement tests including single, repeated, and sustained movements. Forty licensed physical therapists and 40 physical therapy students were provided with operational definitions of the three potential judgments of status change with movement testing; centralization, peripheralization, status quo. All therapists and students viewed the videotape and made a judgment regarding the patient's status change in response to the test. Main Outcome Measure: Percentage agreement and kappa coefficient values for agreement. Results: Interrater reliability was excellent for the total sample of examiners (kappa = .793), for the licensed physical therapists (kappa = .823), and for the students (kappa = .763). Conclusions: Judgments of status change are reliable when operational definitions are provided. Clinical experience does not appear to substantially improve reliability.