Haemophilia A is a disorder of blood coagulation largely affecting males and results from deficiency of factor VIII. It is characterised by a prolonged oozing from wounds after injuries, surgery or tooth extractions. Individuals with severe haemophilia A are often diagnosed before the age of 2 years, and may have frequent spontaneous bleeding, whereas those with moderate or mild disease may not receive a diagnosis until later in life.
10-15% of female carriers may be experience bleeding symptoms, especially after major trauma or surgical procedures.
Coagulation testing for factor VIII activity can determine plasma level and the severity of the deficiency.
Indications for Testing
Diagnostic testing to confirm a clinical diagnosis of haemophilia A.
Testing in relatives of an affected individual for clinical management and genetic counselling. These referrals require that the pathogenic mutation has been identified in the index case.
Prenatal diagnosis, for severe disease and for management of delivery.
In patients with severe haemophilia A, intra-chromosomal inversions involving intron 1 or intron 22 are responsible for approximately half of all cases. Inversions are analysed using test-specific PCR analysis. Sequencing of the protein-coding region is expected to detect >90% of disease alleles in inversion-negative severe patients and in those with moderate and mild disease.
In some individuals, testing for exon deletions/duplications may be appropriate, using multiplex ligation-dependent probe amplification (MLPA).
Venous blood (2-5ml K-EDTA, not to be frozen prior to or during transport)
Genomic DNA (approximately 5μg)
Specimen containers and referral forms must be labelled with at least two corresponding unique identifiers.
Approximately 8 weeks (40 working days) from receipt of sample. A priority service may be available for urgent referrals at an additional cost, please contact the laboratory for further information.
Referrals must generally be made from the Clinical Genetics services or appropriate clinical specialist. It is assumed that informed consent for genetic testing has been obtained from the patient or their parent/guardian and that the implications of a positive result for other family members have been discussed.
Other relevant tests available
Combined analysis of F8 and VWF
Combined analysis of F8 and F9
Haemophilia A gene review http://www.ncbi.nlm.nih.gov/books/NBK1404/
Test options available
(please select from dropdown box at the top of the page or click here)
- Intron 1 and intron 22 inversion analysis by PCR
- NGS of F8 exons 1-26 (entire coding region)
- Dosage analysis using MLPA
- Prenatal diagnosis without maternal cell contamination analysis (haemophilia A and B)
- With maternal cell contamination analysis (autosomal disorders)
Haemophilia A & B/Factor IX deficiency Diagnostic Test