Use of Biomarkers of Inflammation in the Differentiation of Iron Deficiency and Anaemia-Lessons from Inflammatory Bowel Disease

Iron deficiency and iron deficiency anaemia are common in inflammatory bowel disease (IBD), to the detriment of the patients' quality of life. Since ferritin, as an acute-phase protein (APP), has limited diagnostic value in IBD, concurrent assessment of C-reactive protein (CRP) is recommended. The World Health Organization suggests using α1-acid glycoprotein (AGP) as an additional biomarker due to its differing half-life. This study aimed to evaluate ferritin levels in patients with IBD using CRP and AGP, individually and in combination. A total of 118 patients with IBD (mean age: 45.48 ± 15.25 years, 47.46% female) were recruited, including 38 with Crohn's disease, 47 with ulcerative colitis, and 33 controls. The results showed that while CRP alone detected an inflammatory increase in ferritin of 29.76%, this increased to 82.14% when AGP or both AGP and CRP were considered (p < 0.05). Elevated AGP levels were more prevalent in patients with ulcerative colitis. However, concordance between high CRP and AGP levels was confirmed in only 55% of cases. Correcting for inflammation using CRP and/or AGP significantly improved the diagnostic accuracy of ferritin levels in patients with IBD, highlighting the challenge posed by inflammation when assessing iron deficiency.