Assessment of central pain sensitization in chronic low back pain and its utility in diagnosis and prediction of clinical severity

Slowly repeated evoked pain (SREP) is a dynamic pain indicator useful in conditions involving central sensitization. This study evaluated SREP in patients with chronic low back pain (CLBP) and compared it to temporal summation of pain (TSP). The SREP protocol involved nine low-to-moderate painful pressure stimuli (5 s each, 30-s intervals) in 40 patients with CLBP and 40 healthy individuals. Clinical-psychological factors, pain threshold, tolerance, and TSP were assessed. Patients with CLBP showed increasing pain ratings to SREP (0.78 ± 1.05), while healthy individuals did not (-0.44 ± 1.10). No significant group differences were found in TSP, pain threshold and tolerance. SREP effectively distinguished patients with CLBP from healthy individuals (66.3% accuracy), with an optimal cut-off of 0.05 (sensitivity = 77.5%, specificity = 60%), while other pain tests did not. Usual and current pain, central sensitization-related symptoms, and catastrophizing correlated with TSP but not SREP. Sensitization to SREP distinguished patients with CLBP from healthy individuals while TSP did not provide discriminatory ability. However, SREP did not predict clinical severity of the patients, whereas TSP allowed for the prediction of clinical severity. Future development in the application of SREP protocol could help detect and assess the centralized pain component in CLBP.