STarT back Screening Tool (SBT) is a multidimensional screening questionnaire developed for Low Back Pain (LBP) stratification based on some physical and psychological predictors of chronic LBP. The role of physical impairments in the patients' stratification based on SBT remained unclear. In this study we used Discriminant Function Analysis (DFA) to investigate the discriminant ability of the physical factors in comparison to psychological and clinical factors in the categorization of patients with chronic LBP based on SBT in Physical Therapy (PT) settings. Patients with chronic LBP (n = 157) referred for PT treatment, complete a series of questionnaires including SBT and several uni-dimensional psychological and clinical questionnaires. Physical Impairment Index (PII) was used for objective evaluation of physical impairments. DFA revealed that physical, psychological and clinical variables contributed to SBT categorization, however the psychological variables were stronger predictors of SBT categorization than physical variables. Higher correlation between uni-dimensional psychological measurement tools and SBT and relatively lower correlation between objective physical factors and SBT confirmed SBT as a psychological screening questionnaire for patients with chronic LBP.
