Diagnostic applications of newborn screening for alpha-thalassaemias, haemoglobins E and H disorders using isoelectric focusing on dry blood spots

摘要

Background: Neonatal screening for haemoglobin (Hb) disorders is a standard of care in several developed countries with the main objective to detect Hb S. Such practice has not been established in Thailand where alpha-thalassaemia and haemoglobin E (Hb E) are highly prevalent. Early identification of thalassaemias could be helpful and strengthen the programme for prevention and control for severe thalassaemias. Methods: Data from isoelectric focusing (IEF) and Isoscan~R for detecting types and amount (%) of each haemoglobin in 350 newborn's dried blood spots were analysed and compared with the comprehensive genotype analysis by DNA studies as a gold standard. Results: Based on genetic profiles, there were 10 different categories: (I) normal (n = 227), (2) alpha~+-thalassaemia trait (n = 14), (3) alpha~0-thalassaemia trait (n = 13), (4) beta~0-thalassaemia trait (n = 7), (5) Hb E trait (n = 72), (6) Hb E trait with alpha~0-thalassaemia or homozygous alpha~+-thalassaemia (n = 5), (7) Hb E trait with alpha~+-thalassaemia trait (n = 5), (8) homozygous Hb E (n = 3), (9) homozygous Hb E with alpha~0-thalassaemia trait (n = I) and (10) Hb H disease (n = 3). The presence of Hb Bart's and Hb E were used to identify cases with a-thalassaemia and Hb E, respectively. We set 0.25% of Hb Bart's and 1.5% of Hb E as a cut-off level to detect alpha~+-thalassaemia trait (sensitivity 92.86% and specificity 74.0%) and Hb E trait with 100% of both sensitivity and specificity for IEF diagnosis. Conclusion: Although molecular diagnosis seems to be better for definitive diagnosis of thalassaemia syndromes at birth, however, using our reference range described herein, IEF can be applied in a resource-limiting setting with acceptable reliability.