P771 Diagnostic performance of low haemoglobin density (LHD%) for detecting iron deficiency in patients with inflammatory bowel disease

Abstract

In the absence of a feasible, non-invasive gold standard, iron deficiency anaemia (IDA) is best measured using multiple indicators. However, the choice of an appropriate single iron biomarker to replace the multiple-criteria model for IDA screening at the population level continues to be debated. Recently, low haemoglobin density (LHD%) from Coulter counters has been suggested as a useful tool to detect iron deficiency1. Its diagnostic performance in an IBD population has not been evaluated. Using the mathematical sigmoid transformation LHD% = 100×√ (1−(1/(1 + e (1.8 (30-MCHC)))), this study investigated the reliability of LHD% for the assessment of iron status in iron deficiency anaemia (IDA), anaemia of chronic inflammation (ACD) and mixed IDA/ACD. The study population consisted of 93 patients with IBD (53 CD/40 UC, age 36.40 years ±13.14, 67% female), who consecutively attended the Crohn Colitis Centre Rhein-Main, Frankfurt for routine evaluation between October 2014 and November 2017. Blood count, transferrin saturation (TSAT), serum ferritin and C-reactive protein (CRP) were determined by routine assays. Patients with anaemia were classified as having IDA if active inflammation (CRP <5 mg/l) was absent, TSAT<20% and ferritin level <30 µg/l; patients were classified as having ACD if active inflammation was present (CRP ≥5 mg/l),TSAT<20% and ferritin level ≥100 µg/l; patients were classified as having IDA/ACD if active inflammation was present, TSAT< 20% and ferritin level >100 µg/l.2 Receiver operator characteristic (ROC) curves were constructed to evaluate the performance of LHD. Results: In ferropoenic IBD patients, LHD% values (cut-off 4.1%1) were not statistically different in patients with IDA compared with the IDA/ACD group (30.6 vs. 29.3%; p = 0.888). In addition, no significant difference was observed between patients with ACD (LHD 19.1%) compared with the ACD/IDA group (LHD 29.3%, p < 0.281). ROC analysis for LHD% in the detection of iron deficiency showed the following: Area under the curve 0.772; cut-off 4.1%, sensitivity 62.5%, specificity 94.3%. Conclusion: These results clearly demonstrate that LHD% is a reliable biomarker for the detection of iron deficiency in IBD patients with anaemia regardless of whether inflammation is present. Our findings indicate that LHD can provide added value in diagnosing iron deficiency in anaemic IBD patients. 1. Martin-Cabrera P, et al. Clinical use of low haemoglobin density, transferrin saturation, bone marrow morphology, Perl’s stain and other plasma markers in the identification of treatable anaemia presenting for cardiac surgery in a prospective cohort study. J Clin Pathol, 2015;68:923–30. 2. Weiss G, Goodnough LT. Anaemia of chronic disease. N Engl J Med, 2005;352:1011–23.