Pain-related functional interference in patients with chronic neuropathic postsurgical pain: an analysis of registry data

Although chronic postsurgical pain (CPSP) is a major health care problem, pain-related functional interference has rarely been investigated. Using the PAIN OUT registry, we evaluated patients' pain-related outcomes on the first postoperative day, and their pain-related interference with daily living (Brief Pain Inventory) and neuropathic symptoms (DN4: douleur neuropathique en 4 questions) at 6 months after surgery. Endpoints were pain interference total scores (PITS) and their association with pain and DN4 scores. Furthermore, possible risk factors associated with impaired function at M6 were analyzed by ordinal regression analysis with PITS groups (no to mild, moderate, and severe interference) as a dependent three-stage factor, Odds ratios with 95% confidence Intervals were calculated. Of 2322 patients, 15.3% reported CPSP with an average pain score >= 3 (numeric rating scale 0-10). Risk fora higher PITS group increased by 190% (odds ratio [95% confidence interval]: 2.9 [2.7-3.2]; P < 0.001) in patients with CPSP, compared to without CPSP. A positive DN4 independently increased risk by 29% (1.3 [1.12-1.45]; P < 0.001). Preexisting chronic pain (3.6 [2.6-5.1]; P < 0.001), time spent in severe acute pain (2.9 [1.3-6.4]; P = 0.008), neurosurgical back surgery in males (3.6 [1.7-7.6]; P < 0.001), and orthopedic surgery in females (1.7 [1.0-3.0]; P = 0.036) were the variables with strongest association with PITS. Pain interference total scores might provide more precise information about patients' outcomes than pain scores only. Because neuropathic symptoms increase PITS, a suitable instrument for their routine assessment should be defined.