Evaluation of mathematical indices as tools for distinguishing β-thalassemia trait from iron deficiency anemia in Portuguese females with microcytic anemia

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Microcytic anemia is a common condition frequently caused by iron deficiency anemia (IDA) or β-thalassemia trait (BTT). Some mathematical indices have been described as fast and inexpensive tools for distinguishing these two conditions. This approach is very useful in mass screening programs especially in countries with limited resources. This study aimed to evaluate the diagnostic performance of 13 distinct indices: RBC, England&Fraser, Mentzer, Srivastava, Shine&Lal, RDW, Ricerca, Jayabose (RDWI), Green&King (G&K), MDHL, MCHD, Sirdah and Ensani. We investigated 102 adult Portuguese female, presenting anemia (Hb<12g/dL) and microcytosis (MCV<80fL). The HBB gene was screened for pathogenic variants by ARMS or PCR following Sanger sequencing. The iron status was evaluated by standard approaches. IDA was considered when ferritin<12μg/L and/or transferrin saturation<15%. Two groups were generated: 51 BTT (with one HBB variant: c.92+1G>A; c.92+6T>C; c.92+110G>A or c.1188C>T) and 51 IDA, being assured that no individual had simultaneously the two conditions. To determine the performance of the indices, sensitivity, specificity, Youden index (YI) and receiver operating characteristic (ROC) curves were calculated. Due to the high values of AUC (Area Under the Curve) from ROC analysis, a cutoff of 0.70 for the YI was established in order to determine the best formulas. We find that the 3 best performing indices to differentiate the 2 groups were RBC (YI=0.71; AUC=0.902), RDWI (YI=0.84; AUC=0.973) and G&K (YI=0.82; AUC=0.972). Our results suggest a similarity with other Mediterranean countries such as Spain and Greece, where G&K and RDWI also performed above our set cutoff. The same is observed in Brazil probably due to its Portuguese ancestry. We conclude that aiming to diagnosis the condition underlying a microcytic anemia in a female population, there is value in using this method to recognize the individuals suspected of BTT and forward them for HbA2 measurement or HBB molecular test. In the future, a robust group of male patients should be added to the analysis in order to extrapolate which of these indices would best apply to the whole adult Portuguese population.

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