Clinical Significance of C-Reactive Protein Levels in Predicting Responsiveness to Iron Therapy in Patients with Inflammatory Bowel Disease and Iron Deficiency Anemia

Background Iron deficiency anemia (IDA) is a common complication of inflammatory bowel disease (IBD). In clinical practice, many patients receive initial treatment with iron tablets although intravenous (i.v.) iron supplementation is often preferable. Aim This study investigated whether systemic inflammation at initiation of treatment (assessed by C-reactive protein [CRP] and interleukin-6 [IL-6] measurements) predicts response to iron therapy. Methods Data from a previously published phase III trial were retrospectively analyzed after stratification of patients according to baseline CRP (>4 vs. <= 4 mg/L) and IL-6 (>6 vs. <= 6 pg/mL) levels. The study population consisted of patients with Crohn's disease or ulcerative colitis and IDA (Hb <= 110 g/L and TSAT < 20 % or serum ferritin < 100 ng/mL), randomized to either oral (ferrous sulfate) or i.v. iron (ferric carboxymaltose). Results A total of 196 patients were evaluated (oral iron: n = 60; i.v. iron: n = 136). Baseline CRP and IL-6 levels were independent of patients' initial Hb levels and iron status (serum ferritin and TSAT; all p > 0.05). Among iron tablet-treated patients, Hb increase was significantly smaller in the high-versus low-CRP subgroup (1.1 vs. 2.0, 2.3 vs. 3.1, and 3.0 vs. 4.0 g/dL at weeks 2, 4, and 8, respectively; all p < 0.05). Differences were less pronounced with stratification according to baseline IL-6. Response to i.v. iron was mainly independent of inflammation. Conclusions Patients with high baseline CRP achieved a lower Hb response with oral iron therapy. Our results suggest that CRP may be useful to identify IBD patients who can benefit from first-line treatment with i. v. iron to improve their IDA.