Suitability of the Numerical Pain Rating Scale for measuring pain in clinical trials evaluating interventions for people with shoulder disorders according to the OMERACT filter 2.2.

BACKGROUND

The Outcome Measures in Rheumatology (OMERACT) group recommends pain as a core domain in clinical trials for shoulder disorders. This study evaluated the suitability of the Numerical Pain Rating Scale (NPRS) for measuring pain using the OMERACT Filter 2.2.

METHODS

Following the OMERACT Handbook for instrument selection, a systematic review assessed the NPRS's construct validity, reliability, longitudinal construct validity, clinical trial discrimination, and thresholds of meaning. Articles were independently screened, appraised with the COSMIN-OMERACT Good Methods Checklist, and rated as green (good), amber (caution), red (poor), or white (no evidence). Only green and amber studies were included. Findings were summarized in a Summary of Measurement Properties table and discussed at the 2025 OMERACT Shoulder Special Interest Group workshop.

RESULTS

Twelve studies, including 18 pieces of evidence met eligibility criteria. Three studies examined construct validity, two test-retest reliability, four longitudinal construct validity, six clinical trials discrimination and three thresholds of meaning. Six (33%) components of evidence had good methods and were rated green and 12 were rated amber. There was significant heterogeneity in NPRS versions and formats evaluated across studies, questioning the validity of synthesizing the data together. Therefore, 75% of respondents at the 2025 OMERACT conference agreed that synthesizing results from studies using different NPRSs was inappropriate.

CONCLUSIONS

The NPRS cannot progress to the endorsement stage for the core domain of pain for shoulder conditions due to insufficient evidence for any single NPRS version. Current evidence is insufficient to support its use to measure pain in clinical trials of shoulder disorders.