Clustering of patients with chronic low back pain in terms of physical and psychological factors: A cross-sectional study based on the STarT Back Screening Tool

BACKGROUND: The STarT Back Screening Tool (SBT) is a multidimensional questionnaire consisting of physical and psychological factors which categorizes the patients in the low, medium or high risk subgroups. OBJECTIVE: To investigate the relationship between SBT-based subgrouping and clustering of patients with LBP using unidimensional psychological, clinical and physical examination measures. METHODS: One hundred and fifty-seven patients with chronic LBP completed the SBT and uni-dimensional psychological, disability and pain questionnaires. Physical impairments were evaluated through the Physical Impairment Index (PII). Hierarchical and K-means methods were used for cluster analysis. Between-clusters differences and the association between the clusters and SBT-based subgrouping were investigated. RESULTS: Three clusters were identified. The derived clusters were labeled severe, moderate and mild physical-psychologicaldistress clusters, because pain intensity, disability, psychological and physical factors were relatively high, moderate or low, respectively. Most of the patients in moderate and mild physical-psychological distress clusters were categorized as medium risk based on SBT. The mean difference for the PII was higher than that of psychological factors between moderate and mild physical-psychological-distress clusters. CONCLUSIONS: Patients in low and high risk subgroups of SBT were sufficiently differentiated, but patients in a medium risk subgroup had a different profile based on PII. Including additional physical factors in the SBT may be required to better differentiate among patients.