BACK-on-LINE™: A Digital Pain Phenotyping Tool to Personalise Early Self-Management of Low Back Pain: Reliability and Validity in Working Adults

Background and Objective

Low back pain (LBP) is a leading cause of work-related disability. Although early tailored self-management is advocated, current approaches remain generic. Classifying LBP by predominant pain phenotype (nociceptive, neuropathic, nociplastic) may enable targeted self-management, yet practical tools for early or workplace use are limited. This study evaluated the reliability and validity of BACK-on-LINE, a self-administered digital tool differentiating nociceptive and nociplastic pain to support early mechanism-informed self-management in working populations, benchmarked against established patient-reported outcome measures (PROMs).

Methods

Employed adults with LBP (n = 211) recruited from occupational settings completed BACK-on-LINE and PROMs assessing pain (Numeric Pain Rating Scale; NPRS), disability (Roland–Morris Disability Questionnaire; RMDQ), and psychosocial risk (STarT Back Screening Tool; SBST). Reliability was assessed using internal consistency (Cronbach's α) and test–retest reliability (intraclass correlation coefficient; ICC). Validity was examined through convergent validity with PROMs, known-groups validity comparing nociceptive and nociplastic subgroups, and criterion validity using receiver operating characteristic (ROC) analyses against reference standards (pain intensity, disability, chronicity, sickness absence).

Results

Data from 136 participants (64% completion) were analysed. BACK-on-LINE classified 68.4% as nociceptive and 31.6% as nociplastic. Reliability was strong (α = 0.83; ICC = 0.88). Convergent validity was moderate, strongest with SBST (r = 0.67). Known-groups validity was robust, with nociplastic participants reporting higher pain, disability and psychosocial risk (all p < 0.001). Criterion validity was moderate (AUC = 0.67–0.77), with BACK-on-LINE demonstrating comparable or superior discrimination to SBST.

Conclusions

BACK-on-LINE shows good reliability and multi-dimensional validity for self-classifying pain phenotypes in working adults with LBP, offering a scalable approach to support early mechanism-informed self-management in occupational health pathways.

Significance Statement

This study provides robust initial evidence for a self-administered digital tool BACK-on-LINE that enables working adults to self-classify their low back pain into dominant pain mechanism phenotype. By supporting earlier, pain mechanism-informed self-management, it addresses a key gap in workplace back pain support, which is often generic advice poorly tailored. The tool's strength lies in scalability, early application and workplace relevance, outperforming a widely used prognostic tool in this context.