Validity of Current Assessment Tools Aiming to Measure the Affective Component of Pain: A Systematic Review.

The objective of this study was to identify patient-reported outcome measures (PROMs), which aim to measure the affective component of pain and to assess their content validity, unidimensionality, measurement invariance, and Internal consistency in patients with chronic pain. The study was reported according to the PRISMA guidelines. A protocol of the review was submitted to PROSPERO before data extraction. Eligible studies were any type of study that investigated at least one of the domains: PROM development, content validity, dimensionality, internal consistency, or measurement invariance of any type of scale that claimed to measure the affective component of pain among patients with chronic pain. The databases Medline, Embase, PsycINFO, and the Cochrane Library were searched for eligible studies. The database search was supplemented by looking for relevant articles in the reference list of included studies, ie backtracking. All included studies were assessed independently by two authors according to the "COSMIN methodology on Systematic Reviews of Patient-Reported Outcome Measures". Descriptive data synthesis of the identified PROMs was conducted. The search yielded 11,242 titles of which 283 were assessed at the full-text level. Full-text screening led to the inclusion of 11 studies and an additional 28 studies were identified via backtracking, leading to the inclusion of 39 studies in total in the review. Included studies described the development and validity of 10 unique PROMs, all of which we assessed to have potentially inadequate content validity and doubtful psychometric properties. No studies reported whether the PROMs possessed invariant measurement properties. The existing PROMs measuring affective components of chronic pain potentially lack content validity and have inadequate psychometric measurement properties. There is a need for new PROMs measuring the affective component of chronic pain that possess high content validity and adequate psychometric measurement properties.