We have read a letter to the editor in Pain Practice entitled "Confounding factors in predicting acute post-surgical pain," in which the authors raise some methodological concerns regarding our recent study on prediction of postoperative pain. 1 First of all, we thank those authors for acknowledging our study, and we respond below to their relevant concerns regarding potential confounders.Their first concern is on intraoperative use of analgesics and anesthetic management. We started out testing our main study objective-whether pain induced by venous cannulation (VCP) can be used to predict postoperative pain-in a homogeneous and smaller group of adult surgical patients with no pre-existing pain, subjected to scheduled laparoscopic cholecystectomy with highly standardized preemptive analgesia, intraoperative use of anesthetics and analgesics, and postoperative analgesia. In those 150 patients, high responders to VCP (≥2.0 VAS units) had 3.4 times higher risk for moderate postoperative pain than did low responders (<2.0 VAS units) adjusted for age and gender. 2 The present study in 600 patients is a clinical follow-up trial designed to evaluate if the VCP test can also be used in other kinds of surgery in everyday clinical practice. We therefore included patients subjected to different kinds of surgery and anesthesia, well aware that this would give us a highly heterogeneous cohort and enable us to show if this test is also useful in broader perioperative clinical perspectives. 1 We adjusted for intraoperative use of regional anesthesia to take into account the potential influence on immediate postoperative pain levels, as shown in table 5, and found no predictive ability of the VCP test in patients with regional anesthesia, most likely because of their lower levels of acute postoperative pain.Their second concern is on lack of standardization of the postoperative analgesic regimen, which might have had a direct confounding effect on the primary outcome. Certainly, the treatment of postoperative pain was nonstandardized but instead adhered to current clinical practice and standards of care. We strongly believe that high responders to the VCP test also have higher risks for moderate postoperative pain in clinical everyday practice, as indicated by the 1.5 times higher risk found in this heterogeneous group of patients managed according to clinically well-established standards of perioperative care.Regarding their final concern on how data on postoperative pain are obtained, we have read their proposed reference on potential bias from using clinical nurses for data collection in analgesic studies. 3 Since the main purpose of our study 1 was to evaluate the VCP test for postoperative pain prediction in a wide and most relevant perioperative clinical perspective, we still consider it suitable to involve nursing staff normally also used for bedside routine evaluation of postoperative patients. We do not believe our main conclusion to have been influenced by individual differences in assessment of postoperative pain lev...