P187. Comparison of the diagnostic accuracy of the “ferritin/CRP” and the “soluble transferrin receptor (sTfR)” strategies for diagnosing iron deficiency in patients with inflammatory bowel diseases: Results from a prospective study

A. Oussalah¹, I. Aimone-Gastin², S. Salignac³, C. Gurgul², M.‑A. Bigard¹, J.‑L. Guéant², L. Peyrin-Biroulet¹

¹Inserm U954 and Department of Hepato-Gastroenterology, University Hospital of Nancy, Vandoeuvre-lès-Nancy, France; ²Inserm U954, Cellular and Molecular Pathology in Nutrition, Henri Poincaré University Nancy 1, and University Hospital of Nancy, Vandoeuvre-lès-Nancy, France; ³Department of Haematobiology, University Hospital of Nancy, Vandoeuvre-lès-Nancy, France

Background: Iron deficiency (ID) anemia is common in inflammatory bowel diseases (IBD). Current recommendations advocate the use of the “Ferritin/C-reactive protein (CRP)” strategy to assess iron status in IBD patients [1]. The soluble transferrin receptor (sTfR), a truncated form of the membrane-associated transferrin receptor, has been reported to be a sensitive indicator of ID and is not an acute-phase reactant. The value of the serum sTfR has never been evaluated prospectively in patients with IBD. The aim of this study was to evaluate and compare the diagnostic accuracy of “Ferritin/CRP” and sTfR strategies for the appraisal of body iron status in IBD patients.

Methods: All consecutive patients followed in the Nancy IBD cohort and received in the ambulatory outpatient unit were included in the study. Each patient underwent a complete blood count with measurement of the percentage of hypochromic RBC (%hypo-RBC) and a complete biochemical profile including C‑reactive protein, iron status markers (serum iron, ferritin, transferrin, and transferrin saturation coefficient), and serum sTfR. All data were collected prospectively in an electronic database and extracted for the purposes of the study using the GLIMS software. In the “Ferritin/CRP strategy”, ID was defined as ferritin <30 mcg/L in case of CRP ≤5 mg/L or a serum ferritin <100 mcg/L in case of CRP >5 mg/L. In the “sTfR strategy” ID was defined as a sTfR serum concentration >1.76 mg/L (manufacturer's reference values). The gold standard defining ID was a %hypo-RBC >7% and was used as a classification variable in the ROC analysis.

Results: Between March and September 2011, 497 IBD-related hospitalisations were recorded. Serum sTfR was significantly correlated with %hypo-RBC (P < 0.0001). The prevalence of ID according to the “Ferritin/CRP” and “sTfR” strategies was 46.7% and 5.5%, respectively. The agreement between these two strategies was poor (weighted kappa = 0.082). In ROC analysis, the performance of the “sTfR” strategy (AUROC = 0.866) was significantly higher than that of the “Ferritin/CRP” strategy (AUROC = 0.627) (P = 0.0006 for AUROCs comparison). In ROC analysis, the optimal cut-off of the sTfR for diagnosing ID was “>1.29 mg/L” (sensitivity = 83%, specificity = 82%, +LR = 4.52, −LR = 0.21, AUROC = 0.866, P < 0.0001).

Conclusions: In IBD patients, the diagnostic accuracy of the sTfR is higher than that of the “Ferritin/CRP” strategy for the diagnosis of ID.

1. Gasche C, Berstad A, Befrits R, Beglinger C, Dignass A, Erichsen K, Gomollon F, Hjortswang H, Koutroubakis I, Kulnigg S, Oldenburg B, Rampton D, Schroeder O, Stein J, Travis S, Van Assche G. (2007), Guidelines on the diagnosis and management of iron deficiency and anemia in inflammatory bowel diseases. Inflamm Bowel Dis, 1545–53.

Posted in: Poster presentations: Clinical: Diagnosis and outcome (2012)