Test Catalog

Molecular diagnosis of hemophilia B

Code: LRD2222

Type: Estudi de coagulopaties congènites

Clinical information

Diagnostic Utility:

Identifying the molecular defect in the F9 gene in patients diagnosed with HB.

Haemophilia B (HB)

HB is one of the most common bleeding disorders with a prevalence of 1:20,000 males. This bleeding disorder is caused by a deficiency of coagulation factor IX (FIX). Depending on FIX levels, three forms of HB are distinguished: severe if FIX biological activity is <1%; moderate if FIX activity is between 1-5%; mild if FIX activity is between 5-49%. The most common clinical manifestations are internal hemorrhages in joints and muscles, or external bleeding due to minor cuts, dental procedures, or trauma. The frequency and severity of bleeding are inversely proportional to the amount of FIX in the plasma.

HB has an X-linked recessive inheritance, so males are affected and females are carriers of the condition. This disorder is caused by mutations in the F9 gene that can affect the activity of coagulation FIX or reduce the amount of this protein. Currently, over 900 genetic alterations in F9 have been identified. The most common ones describe a change in a single nucleotide of DNA. Several mutations near the start of the F9 sequence cause an unusual form of HB known as HB Leyden. Individuals with these mutations are born with very low levels of functional FIX, but hormonal changes cause the levels of this protein to gradually increase during puberty. As a result, adults with HB Leyden rarely experience episodes of abnormal bleeding.

Application of a multiple gene panel based on the simultaneous amplification of exons and flanking intronic regions for their sequencing by next-generation sequencing (NGS) techniques allows for the simultaneous molecular study of genes related to congenital coagulopathies and hereditary bleeding disorders, including the Factor IX (F9) gene.

Method:

Massive sequencing of the exons and flanking intronic regions of F9 using a panel of genes related to congenital coagulopathies.

Traditional Sanger sequencing to reconfirm the detected mutation(s) in patients diagnosed with HB, in order to reach an unequivocal result by analysing the specific region where the variant is located.

If no potential or definitively causative mutation is identified, the medical team requesting the test will be informed and a discussion about the possibility of performing complementary studies will be held.

Reference Values

Not applicable

Diagnostic Algorithm:

Not applicable

Turnaround Time:

20 working days

Specimen information

Sample: Whole blood
Tube: EDTA K3 tube 5-10 ml if it is a blood sample
Minimum essential volume: 3 ml

Stability:

  • At room temperature: 4 days
  • In refrigeration: 10 days

Transport instructions: Preferably at room temperature

Reason for rejection: Coagulated sample and/or incorrectly identified.

Other types of accepted samples:

  • Purified DNA, minimum 300 ng (30 ng/µL)
  • Buccal mucosa: contact the laboratory for specimen collection specifications.

Administrative information

BST Code: LRD2222
Test Description: Molecular diagnosis of Hemophilia B.
Synonyms: Genetic study of HB, molecular study of Hemophilia B, sequencing of F9.
Section: Congenital Coagulopathies
BST Rate: Check the updated rates here.

The box HEMO. B must be ticked in the molecular study request form, and the phenotypic data available must be filled in.

Profiles:

Not applicable.

References

  • Peter J Hulick. Next-generation DNA sequencing (NGS): Principles and clinical Applications. Waltham, MA: UpToDate Inc. https://www.uptodate.com
  • DNA Sequencing by Capillary Electrophoresis. Applied Biosystems Chemistry Guide. Second Edition.

Base de dades de mutacions