Measurement properties of Visual Analogue Scale, Numeric Rating Scale and Pain Severity subscale of the Brief Pain Inventory in patients with low back pain: a systematic review

Visual Analogue Scale (VAS), Numeric Rating Scale (NRS), and Pain Severity subscale of the Brief Pain Inventory (BPI-PS)] are the most frequently used instruments to measure pain intensity in low back pain (LBP). However, their measurement properties in this population have not been systematically reviewed. The goal of this study was to provide such systematic evidence synthesis. Six electronic sources (MEDLINE, EMBASE, CINAHL, PsycINFO, SportDiscus, Google Scholar) were searched (July 2017). Studies assessing any measurement property in patients with non-specific LBP were included. Two reviewers independently screened articles and assessed risk of bias using the COSMIN checklist. For each measurement property: evidence quality was rated as high, moderate, low, or very low (GRADE approach); results were classified as sufficient, insufficient or inconsistent. Ten studies assessed the VAS, 13 the NRS, four the BPI-PS. The three instruments displayed low or very low quality evidence for content validity. High quality evidence was only available for NRS insufficient measurement error. Moderate evidence was available for: NRS inconsistent responsiveness, BPI-PS sufficient structural validity and internal consistency, and BPI-PS inconsistent construct validity. All VAS measurement properties were underpinned by no, low or very low quality evidence, likewise the other measurement properties of NRS and BPI-PS.