Pain assessment for chronic lower back pain: performance of the PAL-S and PAL-I patient-reported measures for symptoms and impacts

Abstract

Objective: The Patient Assessment for Low Back Pain–Symptoms (PAL-S) and the Patient Assessment for Low Back Pain–Impacts (PAL-I) were developed to incorporate patient perspective of treatment benefit in chronic low back pain (cLBP) trials. This study documents psychometric measurement properties of the PAL-S and PAL-I.Methods: In this multicenter, observational study, eligible participants clinically diagnosed with cLBP provided sociodemographic information and completed PAL measures and other patient-reported outcome measures of pain and/or disability. Confirmatory factor analyses (CFA), construct validity, and reliability were assessed.Results: The 104 participants were 61% female, 89% white, and mean age of 55 years; mean cLBP duration was 11.4 (range 0–47) years. Using painDETECT scores, 36.5% reported small likelihood of neuropathic pain, 30.8% reported unclear likelihood, and 32.7% reported definite likelihood. Persistent pain with pain attacks was reported by 38.5% of participants. CFA confirmed single components with adequate fit indices. Cronbach’s alpha was 0.83 (PAL-S) and 0.87 (PAL-I), indicating reliable scales. Intraclass correlation coefficients (test-retest reproducibility, n = 44) were 0.81 (PAL-S) and 0.85 (PAL-I). PAL-S score correlation was 0.49 with Roland-Morris Disability Questionnaire (RMDQ) and 0.77 with Neuropathic Pain Symptom Inventory (NPSI). PAL-I correlated at 0.73 with RMDQ and −0.60 with Medical Outcomes Study (MOS)−36 Bodily Pain. Both measures significantly differentiated between pain intensity levels (based on numeric response scale) and painDETECT groups.Conclusion: The PAL-S and PAL-I generated highly reliable scores with substantial evidence of construct validity. Routine use of these measures in treatment trials will enhance comparability of LBP-related symptom and impact results, including patient perspective of treatment benefit.