RESUMO
INTRODUCTION: The new red blood cell (RBC) parameters such as reticulocyte haemoglobin content and percentage of hypochromic red cells or equivalent, although useful in the laboratory assessment of iron deficiency anaemia (IDA), are confounded by thalassaemia trait (TT). We aim to evaluate the new red cell parameters on the Beckman Coulter DxH800 in distinguishing between IDA and TT. METHODS: A total of 246 normal subjects, 102 patients with IDA and 115 subjects with TT were accrued for the study. The parameters studied were red blood cell size factor (RSF), low haemoglobin density (LHD%), microcytic anaemia factor (MAF), standard deviation of conductivity of the nonreticulocyte population (SD-C-NRET) and unghosted cell (UGC). Comparison between groups was performed by Student's t-test, and the diagnostic performance was determined by receiver operating characteristic (ROC) curve analysis. RESULTS: Both the LHD% and RSF were significantly higher in IDA than TT, whereas MAF and SD-C-NRET were significantly lower. The SD-C-NRET showed the best diagnostic performance as a single parameter. A formula, [(RBC + Hb) × (HCT + SD-C-NRET)]/RDW-SD, was devised to distinguish between IDA and TT. With a cut-off value of 23, the area under the curve (AUC) was 0.995 (95% CI of 0.99-1.00), the sensitivity was 97%, and the specificity was 99.1%. CONCLUSIONS: The new RBC parameters on Beckman Coulter DxH800 provide useful information in distinguishing between IDA and TT, which is important for clinical decision-making and for streamlining laboratory testing. A new formula is devised that performs better than other discriminant functions in the literature.