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.

Keywords:

• Chronic low back pain
• patient-reported outcome measure
• psychometric properties
• construct validity
• confirmatory factor analysis

Transparency

Declaration of funding

This study was supported by Grünenthal GmbH. Employees of the study sponsor participated in study design, analysis and interpretation of the data, and in the writing of the manuscript. The authors made the decision to submit the article for submission.

Declaration of financial/other relationships

At the time of study conduct, DMB and MLM were employees of Health Research Associates, which received funds to conduct this research; these authors have no financial interests in Grünenthal GmbH. ME, AC, GK, and HL are employees of Grünenthal GmbH. Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Acknowledgements

The authors thank Kelly McCarrier for his contribution to this research and Julia R. Gage (Gage Medical Writing, LLC) for providing medical writing support on behalf of Health Research Associates, Inc.

Data availability statement

Raw data from this study are confidential and are not publicly available.