Phenotypic presentation and underlying mutations in carriers of β‐thalassaemia and α‐thalassaemia in the Danish immigrant population

Abstract

Objective. The thalassaemia syndromes are the most common hereditary diseases in the world and now appear with relatively high frequency in non‐endemic regions. Guidelines recommend the use of mean corpuscular haemoglobin (MCH) alone or in combination with mean corpuscular volume (MCV) in screening for α‐ and β‐thalassaemia. This article deals with the viability of MCV < 78 fL alone as screening parameter for thalassaemia in non‐endemic regions. Material and methods. Data from the Center for Haemoglobinopathies, Herlev University Hospital, consist of MCV measurements from 438 patients with α‐thalassaemia and 450 patients with β‐thalassaemia referred between 1996 and 2005, and simultaneously measured MCV and MCH measurements in 86 patients referred between November 2004 and November 2005. Results. In 450 β‐thalassaemia patients and 117 α⁰‐thalassaemia patients diagnosed between 1996 and 2005, only two β‐thalassaemia patients had MCV ⩾ 78 fL. All α⁰‐thalassaemia patients had MCV < 78 fL. In contrast, 38 % of patients with α⁺‐thalassaemia had MCV > 78 fL. When MCV and MCH were measured simultaneously, one patient with β‐thalassaemia was missed if MCV was used as a screening tool and one patient was missed if MCH was used. Forty‐four different β‐thalassaemic mutations were found. Conclusions. Our data support the notion that the use of MCV < 78 fL instead of MCH < 27 pg is acceptable as a screening criterion in a non‐endemic population. Only 0.5 % of the β‐thalassaemia patients were missed and all the patients with α⁰‐thalassaemia were diagnosed. Since the racial heterogeneity of the immigrant population in non‐endemic regions creates a scenario with a broad spectrum of mutations and haemoglobinopathy, laboratories should be equipped to detect a large variety of mutations.

• Haemoglobinopathies
• MCH
• MCV
• screening
• thalassaemias