The laboratory provides a comprehensive service for alpha thalassaemia offering assistance with full blood count (FBC) and HPLC interpretation as well as a definitive diagnostic service. The genetic diagnosis of alpha thalssaemia follows a simple algorithm, testing for common mutations first followed by testing for rarer forms. After each test there is a clinical review.
The initial screen is a multiplex assay detecting the common alpha thalssaemia deletions. This assay detects the common alpha plus thalasseamia mutations (alpha 3.7kb and 4.2kb deletions) and the alpha zero thalassaemia mutations (SEA, MED, 20.5kb, FIL deletions). Individuals that are negative for the initial screen undergo alpha globin gene sequencing to detect non-deletional alpha thalasaemia mutations. If negative after sequencing patient samples are screened for rarer deletions using Multiplex Ligation-dependent Probe Amplification (MLPA). In rare cases individuals who are carries of epsilon gamma delta beta thalassaemia will also have microcytic hypochromic indices and a normal HbA2 percentage; to exclude these carriers a beta locus MLPA assay is performed.
In general there is good correlation between the phenotype and the genotype, although this can be obscured by iron deficiency. Antenatal referrals for alpha thalassaemia should be made without waiting for iron results. However, genetic testing can take time and a ferritin level could explain the indices in some cases.
The laboratory offers antenatal screening for alpha thalssaemia and can also provide a prenatal diagnostic service for this condition.
Please identify partner in referral if a fetal risk assessment is required.
Please provide full blood count (FBC) and HPLC screening results and iron levels as they become available.
Clotted samples are unsuitable for DNA analysis.
Blood Samples in in correct anticoagulant tubes may be rejected.
We accept DNA samples. Please provide at least 1-5µg of purified DNA
For prenatal diagnosis please refer to section for sample requirements.
Samples must be clearly labelled with the patients first name, surname, D.O.B, hospital number and the date the sample was taken. The details on the sample must correspond to the request form. Unlabelled samples will not be accepted.
Blood Sciences Laboratory
Ground Floor Bessemer Wing
King’s College Hospital
London SE5 9RS
Last updated: 15/01/2020