Sickle cell disease (SCD) is one of the most common genetic diseases, affecting more than 300000 patients in India. It is characterized by homozygous hemoglobin S or other HbS-associated variants. However, large datasets have not been reported. The prevalence of thalassemia is equally high in the Indian population. High-performance liquid chromatography data are now available. However, heterozygosity has not been well studied. HbA2 values require further consideration.

We conducted a prospective observational study to collect data from large cohorts and analyze HbA2 % in relation to hematological parameters in one geographical tribal district. A total of 691 patients, including 575 homozygous (HbSS) and 116 patients with HbS > 50% and HbA2 values ≥ 4%, were reviewed. High-performance liquid chromatography charts were used to differentiate the Hb variants.

The median age of SCD was was16 (interquartile range {IQR] 9-25) years, and 360 (52.1 %)were males. The median A2 was 1.9% (IQR 1.4-2.7) Hb S was 67.9 % (IQR,62.9-72.7), Hb F was 26.2% (IQR 21.5-30.9).There were 116 (16.68 %) patients with HbA2 levels of 4 and above, with a median age of 16.5 (IQR 9-27) years and 59.5 % males. The value of HbA2 % ranged from to 4-8 in 100 patients; one had a value of 37, and remaining between 9-22. This group had median Hb A2 % of median 5.1 (IQR 4.5-6.3) , HbS % of 65.4 (IQR 65.0-70.2) , HbF% of 23.25 (IQR 16.8-29.3)and A0 of 6.6 (IQR 4.4-8.2).The median hematological parameters were Hb 7.8 g/dL (IQR 6.0-9.1), MCV 71.4 fL (IQR 66.8-76.6) , MCH 22.6 pg (IQR 21.1-24.4) , MCHC 31.3 g/dL (IQR 29.9-32.9) Total count 14.4 x103 /µL (IQR 8.6-18.8).A higher HbA2 level was associated with higher MCV (Spearman's rho value 0.008; p =0.01) and positively correlated with MCH (Spearman's rho value=0.003; p =0.01).

In conclusion,the data showed a strikingly high incidence of elevated Hb A2 (16% of the SCD population). Considering the higher-than-normal values of HbA2 in the sickle population in India, it is important to generate even larger data. For better understanding, the molecular classification of patients should be incorporated. Therefore, there is a need to reclassify the levels of HbA2 to qualify for heterozygosity.

Disclosures

No relevant conflicts of interest to declare.

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2024
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