Signs of ongoing inflammation in female patients with chronic widespread pain

This paper looks at the association of inflammatory proteins with chronic widespread pain (CWP), which encompasses a broad range of conditions, including fibromalgia. It is characterized by widespread pain but also frequently includes other symptoms such as depression, fatigue, sleep problems etc. The mechanisms that may trigger the transition from local pain to CWP are unclear, although several physiological and lifestyle risk factors are known. In this study, the aim was to take a broad discovery approach to look for inflammatory proteins associated with CWP, and which might also correlate with the different degrees of pain intensity and pain threshold among patients. 17 female CWP patients and 21 matched controls were examined in the study, and 73/92 INF I proteins were included in the analysis. In the principal analysis of disease vs control levels, 11 proteins were significantly associated with CWP. This “plasma inflammatory profile” included chemokines (MIP1-alpha, CCL28, CCL20), cytokines (CDCP1) and growth factors (LAPTGF-1, HGF), amongst others, strengthening the general view that low-grade inflammation is likely to be a key component of this disease. No good correlation was observed between specific proteins and pain thresholds in CWP, but CCL4, IL-10, CDCP1 and TRAIL were all correlated with reported pain intensities. It was also of interest that there was a very high degree of overlap between the CWP inflammatory profile identified here and the proteins reported as being significantly associated with fibromalgia (Bäckryd et al, 2017, J. Pain Res), and in patients with chronic pain 1 year after disc herniation (Moen et al, 2016, Int. J. Inflamm.) – both of those studies also carried out using Olink panels. This suggests that inflammatory mechanisms may be common across different pain conditions, although with some specific differences. The authors concluded that their results point to the value of a broader approach to biomarker studies compared to narrow hypothesis-driven analysis using a small number of proteins.