Haemoglobin (Hb) variants

Purpose of the test

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.

Sample Requirements

Volume of blood anticoagulated with EDTA:

Adult (16 years and above) 10-15 mls

Children (2-15 years) 5 mls

Infants (0-2 years) 2 mls

Presence of heparin anticoagulant will inhibit PCR applications.

Clotted samples are unsuitable for DNA analysis.

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.

PDF Request Form

Download Haemoglobin (Hb) Variants Request Form

Turnaround Time

DNA analysis in antenatal patients : 2 weeks

Routine samples

Hb variants including Hb S, Hb C, Hb D-Punjab, Hb O-Arab, : 2 weeks

Hb E, Hb Lepore and Hb Kenya by direct analysis

Other Hb variants by re-sequence analysis of DNA : 4-6 weeks

Time Limit for Extra Tests

5 years

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.