Microcytic to hypochromic ratio as a discriminant index of thalassaemia trait in subjects with hypochromic anaemia.

Introduction: Differentiating between thalassaemia and iron deficiency anaemia (IDA) in hypochromic anaemia is a challenge to pathologists as it influences the choice of subsequent specialized confirmatory tests. In this study, we aimed to evaluate the performance of microcytic to hypochromic ratio (MicroR/ Hypo-He, M/H ratio) as a discriminant index in hypochromic anaemia.
Materials and Methods: A retrospective study was carried out on 318 subjects with hypochromic anaemia, which comprised 162 IDA and 156 thalassaemia trait subjects with α-thalassemia, β-thalassemia and HbE trait. Optimal cut-off value, sensitivity and specificity of M/H ratio for thalassaemia trait discrimination was determined using Receiver Operating Characteristic (ROC) analysis.
Results: Subjects with thalassaemia trait showed higher MicroR compared to IDA ( p< 0.001) while subjects with IDA demonstrated higher Hypo-He than thalassaemia trait (p < 0.001). M/H ratio was significantly higher in thalassaemia trait compared to IDA, with medians of 3.77 (interquartile range: 2.57 - 6.52) and 1.73 (interquartile range: 1.27 - 2.38), respectively (p < 0.001). M/H ratio ≥ 2.25 was the optimal cut-off value for discriminating thalassaemia trait from IDA in hypochromic anaemia, with the area under ROC curve (AUC) of 0.83, sensitivity of 80.8% and specificity of 71.6%.
Conclusions: M/H ratio is a useful discriminant index to distinguish thalassaemia trait from IDA in hypochromic anaemia prior to diagnostic analysis for thalassaemia confirmation. High M/H ratio is suggestive of thalassaemia trait than of IDA. However, more studies are required to establish the role of M/H ratio as a screening tool for thalassaemia discrimination in hypochromic anaemia.