Haemoglobin (Hb) variants
- Description
- The most common clinically relevant Hb variants are Hb S (beta codon 6 GAG;Glu ->GTG;Val)., Hb C (beta codon 6 GAG;Glu-> AAG;Lys), Hb D-Punjab (beta 121 GAA;Glu->CAA;Gln), Hb O-Arab (beta 121 GAA;Glu->AAA;Lys), and Hb E (codon 26 (GAG;Glu -> AAG;Lys). These variants can be characterised and presumptively diagnosed using haemoglobin electrophoresis and High Performance Liquid Chromatography (HPLC). For a definitive diagnosis DNA analysis is offered. Sickle cell disease: Seventy per cent of sickle cell disease is caused by homozygosity for the sickle cell mutation located at codon 6 of the beta-globin gene (GAG;Glu ->GTG;Val). This amino acid substitution alters the structure of the globin molecule so that it crystallizes and deforms the red cell into a sickle shape under hypoxic conditions. Twenty-nine per cent of cases are compound heterozygotes for Hb S and Hb C. Less than 1% account for Hb Sβ thalassaemia followed by rarer genotypes of Hb S/D Punjab, Hb S/Lepore and Hb S/O-Arab. Other Hb variants: Most Hb variants are benign affecting both the alpha and beta globin genes. Alteration of the charge of the Hb molecule is detected by haemoglobin electrophoresis, HPLC and Isoelectric Focusing (IEF). Clinical disorders caused by Hb variants include chronic haemolysis, high and low oxygen affinity Hb variants, hypochromic microcytic anaemia e.g. Hb E, Hb Lepore and hyperunstable Hbs. All these variants are identifiable by direct sequence analysis and/or direct mutation analysis.
- Clinical details
- Factors affecting results or interpretation: Presence of heparin anticoagulant will inhibit PCR applications. Clotted samples are unsuitable for DNA analysis. 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.
- Testing site
- Synnovis : Blood Sciences : King's College Hospital
- Laboratory
- Red Cell Centre - Protein
- 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.
- 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.
- Turnaround time
- 20 working days from receipt. For complex cases with additional tests each test will add 10 working days. Antenatal samples 10 working days from sample receipt.
- Cost
- Please contact Business Development for pricing enquiries
- Time limit for extra tests
- 5 years
- Contacts
Special Haematology Department St Thomas’ Hospital
Phone – 020 7188 8189
St Thomas’ Hospital
5th Floor – North Wing
Westminster Bridge Road
London SE1 7EHSpecial Haematology Department at Guy’s Hospital
Phone – 020 7188 3421
Guy’s Hospital
4th Floor – Southwark Wing
Great Maze Pond
London SE1 9RTRed Cell Centre – Protein Laboratory
Phone: 020 3299 2455
Email: kch-tr.redcelllab@nhs.net
Central Specimen Reception
Blood Sciences Laboratory
Ground Floor Bessemer Wing
King’s College Hospital
Denmark Hill
London SE5 9RS