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.
Objective To determine the best threshold value of hemoglobin A2 (HbA2) for diagnosis of β-thalassemia (β-thal) carriers by using high performance liquid chromatography (HPLC), and to improve the application value of HbA2 as a diagnostic index for β-thal carriers to reduce the rates of missed diagnosis and misdiagnosis. Methods Using reverse dot blot (RDB) as a gold standard method, HbA2 results of 1 007 β-thal carriers and 606 normal controls in the past two years determined by HPLC were divided into true positive, false positive, true negative, and false negative based on the different threshold values of HbA2 results. Then, the evaluation indexes such as sensitivity, specificity, positive and negative likelihood ratio, and Youden’s index were evaluated. Next, the receiver operator characteristic (ROC) curve was drawn to determine the best threshold value of HbA2 for diagnosis of β-thal carriers by HPLC. Results If ≥4.0% was taken as the threshold value of HbA2 for diagnosis of β-thal carriers by HPLC, the evaluation indexes values were shown as follows: sensitivity 99.21%, specificity 99.34%, positive likelihood ratio 150.30, negative likelihood ratio 0.008, and Youden’s index 0.99. The Youden’s index was better than the other threshold values, and the corresponding tangent point was the peak point of the ROC curve. Conclusion When ≥4.0% serves as the best threshold value of HbA2 for diagnosis of β-thal carriers using HPLC, integrated evaluation performance of the corresponding sensitivity and specificity is the most ideal, and the authenticity of the diagnostic test is the best.
β thalassemia is a hereditary hemolytic disease caused by the defect of β globin gene. Transfusion-dependent β thalassemia patients need long-term blood transfusion to survive, and a series of systemic and ocular complications will occur in the disease itself and long-term blood transfusion. Retinal blood vessel density decreases, retinal thickness thinned and elastic pseudoxanthoxanoma syndrome are found in fundus due to long-term anemia and side effects of iron chelating agent. At present, there are few reports about eye changes in thalassemia patients, and the cognition is relatively scarce. Therefore, it is necessary to be vigilant for physicians, deeply explore the cause and symptomatic treatment, combined with individual disease characteristics, to provide a more scientific and accurate plan for clinical treatment.