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

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.

Mixed-methods development of a new patient-reported outcome instrument for chronic low back pain: part 2-The Patient Assessment for Low Back Pain-Impacts (PAL-I).

We describe qualitative and quantitative development and preliminary validation of the Patient Assessment for Low Back Pain-Impacts (PAL-I), a patient-reported outcome measure for use in chronic low back pain (cLBP) clinical trials. Concept elicitation and cognitive interviews (qualitative methods) were used to identify and refine symptom concepts. Classical test theory and Rasch measurement theory (quantitative methods) were used to evaluate item-level and scale-level performance of the PAL-I using an iterative approach between qualitative and quantitative methods. Patients with cLBP participated in concept elicitation interviews (N = 43), cognitive interviews (N = 38), and assessment of paper-to-electronic format equivalence (N = 8). A web-based sample of self-reported patients with cLBP participated in quantitative studies to evaluate preliminary (N = 598) and revised (n = 401) drafts and patients with physician-diagnosed cLBP (N = 45) participated in preliminary validation of the PAL-I. The instrument contained 9 items describing cLBP impacts (walking, sitting, standing, lifting, sleep, social activities, travelling, climbing, and body movements). Item-level performance, scale structure, and scoring seemed to be appropriate. One-week test-retest reproducibility was acceptable (intraclass correlation coefficient 0.88 [95% confidence interval, 0.78-0.94]). Convergent validity was demonstrated with PAL-I total score and Roland-Morris Disability Questionnaire (Pearson correlation 0.82), MOS-36 Physical Functioning (-0.71), and MOS-36 Bodily Pain (-0.71). Individual item scores and total score discriminated between numeric rating scale tertile groups and painDETECT categories. Interpretation of paper and electronic administration modes was equivalent. The PAL-I demonstrated content validity and is potentially useful to assess treatment benefit in clinical trials of cLBP therapies.

Mixed-methods development of a new patient-reported outcome instrument for chronic low back pain: part 1-the Patient Assessment for Low Back Pain - Symptoms (PAL-S).

We describe the mixed-methods (qualitative and quantitative) development and preliminary validation of the Patient Assessment for Low Back Pain-Symptoms (PAL-S), a patient-reported outcome measure for use in chronic low back pain (cLBP) clinical trials. Qualitative methods (concept elicitation and cognitive interviews) were used to identify and refine symptom concepts and quantitative methods (classical test theory and Rasch measurement theory) were used to evaluate item- and scale-level performance of the measure using an iterative approach. Patients with cLBP participated in concept elicitation interviews (N = 43), cognitive interviews (N = 38), and interview-based assessment of paper-to-electronic mode equivalence (N = 8). A web-based sample of patients with self-reported cLBP participated in quantitative studies to evaluate preliminary (N = 598) and revised (n = 401) drafts and a physician-diagnosed cohort of patients with cLBP (N = 45) participated in preliminary validation of the measure. The PAL-S contained 14 items describing symptoms (overall pain, sharp, prickling, sensitive, tender, radiating, shocking, shooting, burning, squeezing, muscle spasms, throbbing, aching, and stiffness). Item-level performance, scale structure, and scoring seemed to be appropriate. One-week test-retest reproducibility was acceptable (intraclass correlation coefficient 0.81 [95% confidence interval, 0.61-0.91]). Convergent validity was demonstrated with total score and MOS-36 Bodily Pain (Pearson correlation -0.79), Neuropathic Pain Symptom Inventory (0.73), Roland-Morris Disability Questionnaire (0.67), and MOS-36 Physical Functioning (-0.65). Individual item scores and total score discriminated between numeric rating scale tertile groups and painDETECT categories. Respondent interpretation of paper and electronic administration modes was equivalent. The PAL-S has demonstrated content validity and is potentially useful to assess treatment benefit in cLBP clinical trials.