Reliability of C-reactive protein as an inflammatory marker in patients with immune-mediated inflammatory diseases and liver dysfunction

OBJECTIVES: CRP is an acute-phase reactant widely used clinically as a marker of inflammation. CRP is a protein synthesized by hepatocytes. Previous studies have shown lower CRP levels in response to infections in patients with chronic liver disease. We hypothesized that CRP levels would also be lower during active immune-mediated inflammatory diseases (IMIDs) in patients with liver dysfunction. METHODS: This retrospective cohort study used Slicer Dicer in Epic, our electronic medical record system, to search for patients with IMIDs both with and without concomitant liver disease. Patients with liver disease were excluded if there was no clear documentation of liver disease staging. Patients were also excluded if a CRP level was not available during disease flare or active disease. Arbitrarily, we considered normal CRP as ≤0.7 mg/dl, mild elevation of CRP as ≥0.8 and <3mg/dl, and elevated CRP as ≥3mg/dl. RESULTS: We identified 68 patients with both liver disease and IMIDs (RA, PsA and PMR) and 296 patients with autoimmune disease and without liver disease. Presence of liver disease had the lowest odds ratio (odds ratio = 0.25, P < 0.0001) of having an elevated CRP during flare. Each specific IMID, except SLE and IBD, had higher median CRP levels during active disease episodes in patients without liver disease than in those with liver disease. DISCUSSION: Overall, IMID patients with liver disease had lower serum CRP levels during active disease than their counterparts without liver dysfunction. This observation has implications for clinical use of CRP level as a reliable marker of disease activity in patients with IMIDs and liver dysfunction.