Congenital Adrenal Hyperplasia - RRPL
Discipline
Genetics and Genomics
Overview
Description
Ordering recommendations
- This test can used as part of an algorithm for disorders with a suspected deficiency of 21-hydroxylase (CYP21) or 11-beta-hydroxylase (CYP11B1).
Ordering requirements
- This test has been pre-approved for select medical specialties as indicated (Physician Approval to Order)
- Other physicians may inquire about getting their patient tested through the Genetics Resource Centre process
- Rush/urgent cases must be indicated on the requisition along with an e-mail to RRPLMolecularGenetics@saskhealthauthority.ca.
- If this test will impact an ongoing pregnancy, also fax an urgent referral to the division of medical genetics: 306-655-1736 (otherwise see Genetic Resource Centre process)
Alias
- CAH, CYP21A2, CYP11B1
Specimen Information
Specimen types accepted
- Whole blood: Lavender (EDTA) 4.0 mL
Specimen collection container
- Preferred collection container: Lavender (EDTA) 4.0 mL
- Alternative collection container: Microcollection - EDTA
Required volume
- Optimal folume: 8 mL
- Minimum volume: 0.5 mL
- Pediatric volume: 0.5 – 3 mL
EDTA tubes should be completely full, 2/3 full at minimum, testing may be affected by partial draw
- For patients over 20 kg: 2 EDTA tubes each containing 3.0 mL of blood
- For patients up to 20 kg: 2 EDTA tubes each containing 2.0 mL of blood
- For neonates: 1 EDTA containing a minimum of 0.5 mL of blood
Transport and stability
- Specimen specific storage and transport instructions (ex. Frozen, ship on ice, temperature specification)
- Room temperature: if being shipped on same day of collection (preferred).
- Refrigerated: If shipping is delayed
Performance
Methodology
- Purpose of test (brief): In 90-95% of cases, congenital adrenal hyperplasia (CAH) can be confirmed by finding a mutation in the CYP21A2 gene, which encodes for an enzyme that controls cortisol and aldosterone production. Diagnosis of the 21-OHD CAH can also be confirmed biochemically with a very high concentration of 17-hydroxyprogesterone (17-OHP). Newborn screening for CAH, which utilizes 17 hydroxyprogesterone levels, is a useful tool for early detection of CAH prior to the development of adrenal crisis in the affected neonate. However, screening is associated with a high rate of false positive results and this molecular genetics test should be considered as a second-tier screening test. Other genes are less frequently involved in CAH but this test panel also covers the second most common cause due to 17-alpha-hydroxylase deficiency.
- How testing is performed: Referred out. MLPA: Detects dosage changes in CYP21A2 and CYP21P genes caused by deletions, duplications and gene conversions. Sanger sequencing: Analysis of all coding regions of CYP21A2 and CYP11B1.
- Clinical result interpretations: Interpretation provided on report.
Specimen retention time
- For more information, please visit the RRPL Requisitions and Completion Aids page.
Last Updated: March 28, 2024