Compromising for carrier detection of beta thalassemia based on measurement of HbA2 levels in unusual cases.

An increased HbA2 level is the hallmark for identification of β thalassemia carriers. However, in some carriers the level of HbA2 is not typically elevated creating difficulties in making a diagnosis. We describe a family having an affected child referred to us for confirmation of diagnosis of β thalassemia. The father has a classical β thalassemia trait and the mother showed typical reduced red cell indices with a high RBC count but the HbA2 level was normal (2.4%). On molecular analysis she was a heterozygous carrier having IVS1 nt 5 (G→C) β thalassemia mutation. Further analysis of δ globin gene showed that the reduction in HbA2 was due to the presence of the δ mutation HbA2 Pelendri [CD 141(Leu→Pro, CTG→CCG)]. The diagnosis of a β thalassemia carrier could have been compromised, and states the importance of comprehensive molecular analysis for accurate diagnosis in couples where one partner has β thalassemia trait.