Background: In the absence of a feasible, non-invasive gold standard, iron deficiency anaemia (IDA) is best measured by the use of multiple indicators. However, the choice of an appropriate single iron biomarker to replace the multiple-criteria model for screening for IDA at the population level continues to be debated. Recently low haemoglobin density (LHD%) from Coulter counters has been suggested as a usefull tool to detect iron deficiency . 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.
Methods: The study population consisted of 84 patients (34 male, 50 female) with IBD (age, 36.40±13.14 years, 40% male), who consecutively attended the Crohn Colitis Centre Frankfurt for routine evaluation between October 2014 and September 2016. Blood count, transferrin saturation (TSAT), serum ferritin (SF), C-reactive protein and ZPP were determined by routine assays. Patients with anaemia were classified as having IDA if active inflammation (CRP <5mg/L) was absent and TSAT <20% and ferritin level <30 μg/L; Patients were classified as having ACD if active inflammation was present (CRP ≥5mg/L) and TSAT <20% and ferritin level ≥100μg/L; Patients were classified as having IDA/ACD if active inflammation was present and TSAT<20% and ferritin level >100μg/L . Receiver operator characteristic (ROC) curves were constructed to evaluate the performance of LHD.
Results: In ferropoenic IBD patients (IDA and IDA/ACD), the values obtained for LHD% showed no statistical difference (p>0.5). Significant differences were detected when patients with ACD (LHD% 10.5%) were compared with the ACD/IDA group (LHD 24.1%, p=0.0001). ROC analysis for LHD% in the detection of iron deficiency showed the following: area under curve 0.903; cut off 5.5%, sensitivity 88.6%, specificity 76.9%.
Conclusions: These results clearly demonstrate that LHD% is a reliable biomarker for the detection of iron deficiency in IBD patients with anemia in both the presence and absence of inflammation. Our findings indicate that LHD can provide added value in diagnosing iron deficiency in anaemic IBD patients.
 Urrechaga E wet al. Low hemoglobin density potential marker of iron availability. Int J Lab Hematol. 2012;34:47–51
 Weiss G, Goodnough LT. Anemia of chronic disease. N EnglJ Med 2005;352:1011–23