Unresolved laboratory issues of the heterozygous state of β-thalassemia: a literature review

Abstract

Although considered a mild clinical condition, many laboratory issues of the carrier state of beta-thalassaemia remain unresolved. Accurate laboratory screening of beta-thalassaemia traits is crucial for preventing the birth of a beta-thalassaemia major child. Identification of carriers in the laboratory is affected by factors that influence red cell indices and HbA2 quantification. Silent mutations and co-inheriting genetic and non-genetic factors affect red cell indices which decreases the effectiveness of the conventional approach. Similarly, the type of beta mutation, co-inheriting genetic and non-genetic factors, and technical aspects, including the analytical method used and variations in the HbA2 cutoff values, affect the HbA2 results leading to further confusion. However, the combination of MCV, MCH and haemoglobin analysis increases the diagnostic accuracy. Diagnostic problems arising from non-genetic factors can be eliminated by carefully screening the patient's clinical history. Still, issues due to certain genetic factors, such as Krüppel-like factor 1 gene mutations and alpha triplication remain unresolved. Each laboratory should determine the populationspecific reference ranges and be wary of machine-related variations of HbA2 levels, the prevalence of silent mutations in the community.