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

Although considered a mild clinical condition, many laboratory issues of the carrier state of β-thalassemia remain unresolved. Accurate laboratory screening of β-thalassemia traits is crucial for preventing the birth of a β-thalassemia 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 β mutation, co-inheriting genetic and non-genetic factors, and technical aspects, including the analytical method used and variations in the HbA2 cut-off values, affect the HbA2 results, leading to further confusion. However, the combination of mean corpuscular volume, mean corpuscular hemoglobin, and hemoglobin analysis increases the diagnostic accuracy. Diagnostic problems arising from non-genetic factors can be eliminated by carefully screening the patient's clinical history. However, issues due to certain genetic factors, such as Krüppel-like factor 1 gene mutations and α triplication still remain unresolved. Each laboratory should determine the population-specific reference ranges and be wary of machine-related variations of HbA2 levels, the prevalence of silent mutations in the community.