Evaluation of Clinical Application of Hb-A2 Level for Detection of Thalassemia Carrier

Objective To evaluate the clinical application of Hb A2 detection of thalassemia including alpha thalassemia and beta thalassemia. Methods There were 70 Southeast Asia type alpha thalassemia heterozygosity and 43 normal gene type resulted from Gap PCR, and 33 beta thalassemia heterozygosity and 36 normal gene type diagnosed by reverse dot blot (RDB). Cutoff value of Hb A2 in finding of alpha thalassemia and beta thalassemia was present.The sensitivity, specificity, positive and negative likelihood ratio, and receiver operator characteristic curve (ROC) were used to evaluate the significance of Hb A2 level in screening thalassemia in adults. Results The borderline values between normal and pathological range of Hb A2 were ≤2 6% in alpha thalassemia and ≥3 8% available in beta thalassemia. Sensitivity and specificity were 59% and 54% in alpha thalassemia, 76% and 83% in beta thalassemia, respectively. ROC showed that the area covered beneath the curve of beta thalassemia was more than that of alpha thalassemia. Conclusions The cutoff between normal and pathological range of Hb A2 is ≤2 3% in alpha thalassemia and ≥3 8% in beta thalassemia. Hb A2 detection has higher sensitive and specific in beta thalassemia diagnosis, but lower in alpha thalassemia diagnosis