Systemic alterations in plasma biomarkers levels in patients with chronic pain

ABSTRACT BACKGROUND AND OBJECTIVES: To analyze the scientific evidence on the changes in plasma levels of interleukins, nitric oxide, extracellular matrix metalloproteinases, bradykinins, and cortisol in patients with chronic pain. CONTENTS: The studies were identified by searching the following electronic databases: Pubmed/Medline, Scopus, LILACS, and Web of Science, published from June of 2016 to December of 2016. The selected articles were presented in a flow chart based on their identification, selection, eligibility and inclusion and exclusion criteria. The content of the articles included in the study was analyzed to identify the biomarkers present in patients with chronic pain. Thirteen articles that addressed the plasma biomarkers levels in humans with chronic pain were selected. Most of the articles presented the cytokines levels, followed by cortisol. Only one article mentioned the nitric oxide, and none mentioned what plasma levels of extracellular matrix metalloproteinases and bradykinins were identified. CONCLUSION: Changes were observed in inflammatory and anti-inflammatory cytokine plasma levels, and that cortisol is related to anxiety and depression symptoms in patients with chronic pain. However, it was not possible to identify the changes in plasma levels of nitric oxide, bradykinin, and extracellular matrix metalloproteinases due to the absence of scientific evidence.