Validation of the work ability index-single item and the pain disability index-work item in patients with chronic low back pain.

Purpose: A cross-sectional and longitudinal study was conducted to analyse construct validity, responsiveness, and Minimal Clinically Important Change (MCIC) in the Work Ability Score (WAS) and Pain Disability Index Work item (PDI-W) in patients with Chronic Low Back Pain (CLBP).

Method: Construct validity was assessed by testing predefined hypotheses. Responsiveness and MCIC were measured with an anchor-based method.