The percentage of hypochromic red cells (%Hypo) is a diagnostic tool that has been used with biochemical markers to diagnose iron disturbances and is incorporated to National Kidney Foundation KDOQI guidelines for monitoring recombinant human erythropoietin therapy. %Hypo measurement has been restricted to analysers manufactured by Siemens. Low haemoglobin density (LHD%), a new parameter provided by Beckman-Coulter, is derived from the traditional mean cell haemoglobin concentration (MCHC), using the mathematical sigmoid transformation
This study aimed to establish LHD% values in the normal population and in different types of anaemia, to investigate its clinical usefulness in the study of iron status and its correlation with %Hypo. Samples from 449 patients [120 healthy individuals, 86 iron deficiency anaemia (IDA), 102 chronic kidney disease, 58 anaemia of chronic disease and 83 β-thalassaemia carriers] were run sequentially on the LH 750 (Beckman-Coulter) and Advia 2120 (Siemens) analysers. The reliability of LHD% as a marker of iron deficiency was evaluated on a group of 152 consecutive patients with IDA. Good correlation was observed between %Hypo and LHD%, r2 = 0.869. Receiver operating characteristic curve analysis for LHD% and the diagnosis of iron deficiency was: cut-off point 4.0%; area under the curve 0.976; sensitivity 95.2%; specificity 93.3%. There was a good level of agreement between LHD% and %Hypo. Both are suitable parameters for determining iron status and its availability for erythropoiesis, with the same clinical significance.