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Abstract: Chronic pain affects more than 50 million Americans. Treatments remain inadequate, in large part, because the pathophysiological mechanisms underlying the development of chronic pain remain poorly understood. Pain biomarkers could potentially identify and measure biological pathways and phenotypical expressions that are altered by pain, provide insight into biological treatment targets, and help identify at-risk patients who might benefit from early intervention. Biomarkers are used to diagnose, track, and treat other diseases, but no validated clinical biomarkers exist yet for chronic pain. To address this problem, the National Institutes of Health Common Fund launched the Acute to Chronic Pain Signatures (A2CPS) program to evaluate candidate biomarkers, develop them into biosignatures, and discover novel biomarkers for chronification of pain after surgery. This article discusses candidate biomarkers identified by A2CPS for evaluation, including genomic, proteomic, metabolomic, lipidomic, neuroimaging, psychophysical, psychological, and behavioral measures. Acute to Chronic Pain Signatures will provide the most comprehensive investigation of biomarkers for the transition to chronic postsurgical pain undertaken to date. Data and analytic resources generatedby A2CPS will be shared with the scientific community in hopes that other investigators will extract valuable insights beyond A2CPS's initial findings. This article will review the identified biomarkers and rationale for including them, the current state of the science on biomarkers of the transition from acute to chronic pain, gaps in the literature, and how A2CPS will address these gaps., (Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the International Association for the Study of Pain.)

Purpose: The current study aimed to identify patients presenting with acute pain who may be at risk for a complicated trajectory, via identifying clusters of early opioid prescribing patterns., Methods: National Veterans Affairs administrative data were utilized to build a cohort of outpatients with acute pain presentations and no more than minimal opioid use in the prior year. Latent Class Analyses (LCAs) identified clusters of early opioid prescribing patterns. The risk of progression to long-term opioid use was contrasted between LCA clusters using log-binomial regression, adjusting for confounding variables., Results: The 2018 cohort included N = 191,283. Among the 27,890 who received an initial opioid prescription, LCA classes were identified using: first supply day, total days dispensed across 30 days, opioid type, dose and number of prescriptions across the first 30 days. In the three-class model: class 1 indicated an immediate, low-dose and brief supply; class 2 included delayed, low-dose and longer duration prescriptions and class 3 included delayed, high-dose and moderate duration prescriptions. Adjusted relative risk ratios for progression to long-term opioid use in the following year were 3.33 (95% CI: 2.71-4.10) for class 1 (absolute risk 1.1%); 7.76 (95% CI: 6.69-8.99) for class 2 (3.1%) and 6.81 (95% CI: 5.72-8.12) for class 3 (2.4%) compared to patients who did not receive an acute opioid prescription (0.3%)., Conclusions: These clusters of acute opioid prescribing could facilitate the identification of patients who may benefit from enhanced pain care earlier in the pain trajectory and decrease future reliance on long-term opioid therapy., (© 2022 European Pain Federation - EFIC®.)

Patients undergoing thoracic surgery experience particular challenges for acute pain management. Availability of standardized diagnostic criteria for identification of acute pain after thoracotomy and video assisted thoracic surgery (VATS) would provide a foundation for evidence-based management and facilitate future research. The Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION) public-private partnership with the United States Food and Drug Administration, the American Pain Society (APS), and the American Academy of Pain Medicine (AAPM) formed the ACTTION-APS-AAPM Pain Taxonomy (AAAPT) initiative to address absence of acute pain diagnostic criteria. A multidisciplinary working group of pain experts was invited to develop diagnostic criteria for acute thoracotomy and VATS pain. The working group used available studies and expert opinion to characterize acute pain after thoracotomy and VATS using the 5-dimension taxonomical structure proposed by AAAPT (i.e., core diagnostic criteria, common features, modulating factors, impact/functional consequences, and putative mechanisms). The resulting diagnostic criteria will serve as the starting point for subsequent empirically validated criteria. PERSPECTIVE ITEM: This article characterizes acute pain after thoracotomy and VATS using the 5-dimension taxonomical structure proposed by AAAPT (ie, core diagnostic criteria, common features, modulating factors, impact and/or functional consequences, and putative mechanisms)., (Copyright © 2021 United States Association for the Study of Pain, Inc. Published by Elsevier Inc. All rights reserved.)

Objective: Define and contrast acute pain trajectories vs. the aggregate pain measurements, summarize appropriate linear and nonlinear statistical analyses for pain trajectories at the patient level, and present methods to classify individual pain trajectories. Clinical applications of acute pain trajectories are also discussed., Setting: In 2016, an expert panel involving the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION), American Pain Society (APS), and American Academy of Pain Medicine (AAPM) established an initiative to create a pain taxonomy, named the ACTTION-APS-AAPM Pain Taxonomy (AAAPT), for the multidimensional classification of acute pain. The AAAPT panel commissioned the present report to provide further details on analysis of the individual acute pain trajectory as an important component of comprehensive pain assessment., Methods: Linear mixed models and nonlinear models (e.g., regression splines and polynomial models) can be applied to analyze the acute pain trajectory. Alternatively, methods for classifying individual pain trajectories (e.g., using the 50% confidence interval of the random slope approach or using latent class analyses) can be applied in the clinical context to identify different trajectories of resolving pain (e.g., rapid reduction or slow reduction) or persisting pain. Each approach has advantages and disadvantages that may guide selection. Assessment of the acute pain trajectory may guide treatment and tailoring to anticipated symptom recovery. The acute pain trajectory can also serve as a treatment outcome measure, informing further management., Conclusions: Application of trajectory approaches to acute pain assessments enables more comprehensive measurement of acute pain, which forms the cornerstone of accurate classification and treatment of pain., (© The Author(s) 2021. Published by Oxford University Press on behalf of the American Academy of Pain Medicine.)

Objective: The goal of this post hoc analysis of subjects from a prospective observational study was to identify the predictors of patients developing moderate to severe acute pain (mean numerical rating scale [NRS] ≥4, 0-10) during the first three days after video-assisted thoracoscopic surgery (VATS) from a comprehensive evaluation of demographic, psychosocial, and surgical factors., Methods: Results from 82 patients who were enrolled one week before VATS and evaluated during the first three postoperative days are presented. The primary outcome variable of the current study was the presence of moderate to severe acute pain after VATS., Results: Fifty-nine percent (95% confidence interval, 47-69%) of study subjects developed moderate to severe acute pain after VATS. Factors univariately associated with the presence of moderate to severe acute pain were greater average expected postoperative pain, greater pain to a suprathreshold cold stimulus, and longer durations of surgery and hospital stay (P < 0.05). When considered in the multiple logistic regression models, the patients' preoperative average intensity of expected postoperative pain (NRS, 0-10) was the only measure associated with the moderate to severe acute pain. Average intensity of postoperative pain expected by patients when questioned preoperatively mediated the effect of reported intensity of pain to the suprathreshold cold stimulus for moderate to severe acute pain levels. Preoperative patient expectations had greater predictive value than other assessed variables including psychosocial factors such as catastrophizing or anxiety assessed one week before surgery., Conclusions: None of the preoperative psychosocial measures were associated with the moderate to severe acute pain after VATS. Average expected postoperative pain was the only measure associated with the development of moderate to severe acute pain after VATS., (© 2018 American Academy of Pain Medicine. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)