A prognostic approach to defining chronic pain across a range of musculoskeletal pain sites
Sara Muller, Elaine Thomas, Kate M Dunn, and Christian D Mallen
Objectives To test whether the prognostic definition of chronic pain, which has previously been applied in specific anatomical areas, performed well in a cohort of older adults with a range of musculoskeletal pain sites. Methods Data are taken from the PROG-RES Study of adults aged ≥50 years consulting their general practitioner with any musculoskeletal pain who completed postal surveys immediately after consultation and 12 months later. Baseline risk of clinically significant pain persisting at 12-months follow-up, defined as a Chronic Pain Grade ≥II, was calculated using the prognostic approach, which includes a range of pain and related factors. The approach was implemented using logistic regression models and performance of the approach, including cut-offs in the score to define groups with differing levels of risk, was assessed in terms of calibration and discrimination. Results Application of the original risk cut-offs created groups with increasing proportions of chronic pain (area under the curve=0.79). However, the probability of chronic pain in each group was higher than expected by the model. New cut-offs were defined for this group of older adults: score ≤5 = probability of chronic pain<20%, ≤ 11 = probability < 50%, ≤ 16 = probability < 80% which resulted in good calibration of the model. Discussion The prognostic approach to defining chronic pain is suitable for use in older adults consulting primary care with musculoskeletal pain at a range of sites, but new cut-offs are needed to allow for the higher risk profile in this group. An adapted version of this method may also have the potential for application directly within the clinical consultation.