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 six 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 (OR) with 95% confidence intervals (CI) were calculated. Of 2,322 patients, 15.3% reported CPSP with an average pain score ≥3 (NRS 0-10). Risk for a higher PITS group increased by 190% (OR (95%-CI): 2.9 (2.7-3.2); p<0.001) in patients with, compared to without CPSP. A positive DN4 independently increased risk by 29% (1.3 (1.12-1.45), p<0.001). Pre-existing 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. PITS might provide more precise information about patients' outcomes than pain scores only. As neuropathic symptoms increase PITS, a suitable instrument for their routine assessment should be defined.

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