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

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 α-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® 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: (1) normal (n = 227), (2) α(+)-thalassaemia trait (n = 14), (3) α(0)-thalassaemia trait (n = 13), (4) β(0)-thalassaemia trait (n = 7), (5) Hb E trait (n = 72), (6) Hb E trait with α(0)-thalassaemia or homozygous α(+)-thalassaemia (n = 5), (7) Hb E trait with α(+)-thalassaemia trait (n = 5), (8) homozygous Hb E (n = 3), (9) homozygous Hb E with α(0)-thalassaemia trait (n = 1) and (10) Hb H disease (n = 3). The presence of Hb Bart's and Hb E were used to identify cases with α-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 α(+)-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.