Alpha thalassaemia

Description: 
The alpha thalassaemias are a group of disorders characterised by a reduction in alpha globin synthesis. Each chromosome carries two copies of the alpha globin gene.

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.
Clinical details: 
Please state if a pregnancy is involved as antenatal work is prioritised.
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.
Sample type and Volume required: 
Volume of blood anticoagulated with EDTA: Adult (16 years and above) 2 x 4 ml, Children (2-15 years) 1 or 2 x 4 ml Infants (0-2 years) 1 ml.
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.
Turnaround time: 
10 working days from sample receipt. For complex cases where additional tests are required each test will add 10 working days. Please note any clinical urgency on the referral form, so samples can be prioritised.
Special sample instructions: 

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.

Storage and transport: 
Blood should be stored at 4°C where possible. Send at room temperature by first class post. If possible, please complete the request form attached and send as a hard copy (do not send electronically) with the sample. This will ensure all relevant information is available and will aid us in processing your test.
Cost: 
Please contact Business Development for pricing enquiries.
Contacts:
Red Cell Centre - Molecular Diagnostics Laboratory
020 3299 1246 / 2265
kch-tr.pnd@nhs.net
c/o Central Specimen Reception
Blood Sciences Laboratory
Ground Floor Bessemer Wing
King’s College Hospital
Denmark Hill
London SE5 9RS
Mon-Fri, 9.00am-5.30pm
For clinical advice or interpretation of results, please contact the laboratory in the first instance.

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Last updated: 15/01/2020