Clinical utility of Abbott Alinity hq extended red blood cell parameters in differentiating β-thalassemia trait and iron deficiency anemia

INTRODUCTION

The objective of the study was to evaluate the performance of the Abbott Alinity hq advanced multi angle polarized scatter separation (MAPSS^TM )-based optical RBC technology, for the differentiation between iron deficiency anemia (IDA) and β-thalassemia carrier status.

METHODS

Four hundred and sixty-four samples were analyzed. 228 were healthy controls, 30 were β-thalassemia carriers, and 40 were IDA. Receiver operating characteristics analysis evaluated the performance of red cell parameters and mathematical formulas.

RESULTS

RBC concentration was the most efficient discriminant (area under the curve; AUC of 0.963, Youden Index of 0.88) followed by red blood cell distribution width in size distribution (AUC of 0.960 and YI of 0.86), and red blood cell distribution width coefficient of variation (AUC of 0.924, and YI of 0.74). The absolute reticulocyte concentration showed good diagnostic efficiency, with AUC of 0.808. Hemoglobin distribution width, the %CV of directly measured cellular hemoglobin concentration, and CHCr, the average hemoglobin concentration of reticulocytes have emerged as novel discriminating parameters, with AUC of 0.749 and 0.785, respectively. The England and Fraser index was the best discriminating mathematical formula based on Youden Index of 0.91. The Ricerca, red blood cell distribution width index, Green and King, and Mentzner Index formulas also showed strong discriminative power. The Shine and Lal index, together with the recent mathematical formula M/H, (ratio of percent microcytic and hypochromic red blood cells) demonstrated moderate performance with AUC of 0.796 and 0.740, respectively.

CONCLUSION

Extended red cell analysis delivered by the advanced optical technology on the Alinity hq hematology analyzer has efficient diagnostic utility in the initial discrimination of the two most common microcytic anemias: IDA and β-thalassemia trait.

KLF1 gene and borderline hemoglobin A2 in Saudi population

INTRODUCTION

Elevated HbA₂ (hemoglobin A₂) level is considered the most reliable hematological parameter for the detection of β-thalassemia carriers. However, some carriers are difficult to recognize because the level of HbA₂ is not in the distinctive carrier range, i.e. 4.0-6.0%; instead, some carriers have HbA₂ levels between normal and carrier levels, i.e. borderline HbA₂ (HbA₂ = 3.1-3.9%). Studies have shown that variations in the erythroid Krüppel-like factor (KLF1) gene lead to borderline HbA₂ in β-thalassemia carriers from various populations. The incidence of borderline HbA₂ in Saudis is high.

MATERIAL AND METHODS

To confirm the influence of variations in KLF1, HBA1, HBA2 and HBB genes for the reduction of the level of HbA₂ in Saudi β-thalassemia carriers, we performed a direct sequence analysis of KLF1, HBA1, HBA2 and HBB genes from 212 healthy Saudis (88 subjects: HbA₂ < 3; 72 subjects: HbA₂ = 3.1 to 3.9; 52 subjects HbA₂ > 4.3).

RESULTS

The presence of the borderline HbA₂ level is not specific to any type of β-thalassemia variation or β⁺-thalassemia variations in Saudis. Two exonic (c.304T>C and c.544T>C) and two 3' untranslated region (3'UTR) (c.*296G>A and c.*277C>G) variations have been identified in the KLF1 gene for the first time from an Arab population. None of these four variations in KLF1 genes are significantly associated with the Saudis with borderline HbA₂. α Globin genotype, -α₂^3.7/α₁α₂, is found to be the most frequent (55.55%) among healthy Saudis with borderline HbA₂ compared with the other groups (HbA₂ < 3 = 20.45%; HbA₂ > 4.3 = 13.51%).

CONCLUSIONS

Further studies are necessary to determine the influence of other factors on the presence of borderline HbA₂ in 41.67% of Saudis.