Phenotypic presentation and underlying mutations in carriers of beta-thalassaemia and alpha-thalassaemia in the Danish immigrant population.
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 alpha- and beta-thalassaemia. This article deals with the viability of MCV<78 fL alone as screening parameter for thalassaemia in non-endemic regions.


METHODS
Data from the Center for Haemoglobinopathies, Herlev University Hospital, consist of MCV measurements from 438 patients with alpha-thalassaemia and 450 patients with beta-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 beta-thalassaemia patients and 117 alpha0-thalassaemia patients diagnosed between 1996 and 2005, only two beta-thalassaemia patients had MCV>or=78 fL. All alpha0-thalassaemia patients had MCV<78 fL. In contrast, 38% of patients with alpha+-thalassaemia had MCV>78 fL. When MCV and MCH were measured simultaneously, one patient with beta-thalassaemia was missed if MCV was used as a screening tool and one patient was missed if MCH was used. Forty-four different beta-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 beta-thalassaemia patients were missed and all the patients with alpha0-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.
Kornblit
B
B
Center for Haemoglobinopathies, Department of Haematology, Herlev Hospital, University of Copenhagen, Herlev, Denmark.
Hagve
T-A
TA
Taaning
P
P
Birgens
H
H
D003718:Denmark / Q000453:epidemiology; D004641:Emigration and Immigration; D004909:Erythrocyte Indices / Q000235:genetics*; D006580:Genetic Carrier Screening / Q000379:methods*; D006801:Humans; D008403:Mass Screening / Q000379:methods*; D011295:Prenatal Care / Q000379:methods*; D012016:Reference Values; D012680:Sensitivity and Specificity; D017085:alpha-Thalassemia / Q000097:blood* / Q000208:ethnology / Q000235:genetics; D017086:beta-Thalassemia / Q000097:blood* / Q000208:ethnology / Q000235:genetics