The use of a classification approach to identify subgroups of patients with acute low back pain - Interrater reliability and short-term treatment outcomes

Study Design. A prospective, consecutive, cohort Study of patients with acute low back pain classified into subgroups based on examination data and treated with a specific treatment approach. Objective, To calculate the interrater reliability of a classification system, and to compare initial patient characteristics and outcomes of physical therapy treatment when a classification approach is used. Summary of Background Data. Classification of patients with low back pain into homogeneous subgroups has been identified as a research priority. Identifying relevant subgroups of patients could improve clinical outcomes and research efficiency. Methods. Consecutive patients referred to physical therapy for treatment of acute low back pain were evaluated and classified into one of four subgroups (immobilization, mobilization, specific exercise, or traction) before treatment, Physical therapy treatment was based on the patient's classification. The classifications were compared for initial patient characteristics, frequency and duration of physical therapy, and improvement in Oswestry scores; Results, In this study, 120 patients were evaluated and classified. Analysis of interrater reliability showed a kappa value of 0.56. Differences were found among the classifications for age, initial Oswestry score, history of low back pain, symptom distribution, and average change in Oswestry score with treatment. Conclusions. Reaching a consensus regarding relevant patient subgroups requires data on the reliability and validity of existing classification systems. Further work is required to validate improvement in treatment outcomes using a classification approach.