Discussion
The observations from this study indicate that unique pain experiences within the chronic pancreatitis population can be associated with distinct biochemical signatures. These data indicate that further hypothesis-driven analyses combining biochemical measurements and detailed pain phenotyping could be used to develop precision approaches for pain management in patients with chronic pancreatitis.
Methods
Cytokines, chemokines, and peptides associated with nociception and pain were measured in legacy serum samples from CP patients (N = 99) enrolled in the North American Pancreatitis Studies. The unsupervised hierarchical cluster analysis was applied to cluster CP patients based on their biomarker profile. Classification and regression tree was used to assess whether these biomarkers can predict pain outcomes.
Results
The hierarchical cluster analysis revealed a subset of patients with predominantly constant, mild-moderate pain exhibited elevated interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-2 (IL-2), tumor necrosis factor alpha (TNFα), and monocyte chemoattractant protein-1 (MCP1) whereas patients with higher interleukin-4 (IL-4), interleukin-8 (IL-8) and calcitonin gene related peptide (CGRP) were more likely to have severe pain. Interestingly, analyses of each individual biomarker revealed that patients with constant pain had reduced circulating TNFα and fractalkine. Patients with severe pain exhibited a significant reduction in TNFα as well as trends towards lower levels of IL-6 and substance P.