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Lab Dept:
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Anatomic Pathology
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Test Name:
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CYP21A2 (CAH) EVALUATION SEQUENCING
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General Information
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Lab Order Codes:
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CYPA
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Synonyms:
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Congenital Adrenal Hyperplasia Evaluation Sequencing; CYP21A2 Sequencing; 21-Hydroxylase Gene Sequencing
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CPT Codes:
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81405 – Molecular Pathology procedure, Level 6
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Test Includes:
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CYP21A2 full gene analysis (amplification) and CYP21A2 gene sequencing will always be performed. DNA extraction will always be performed at an additional charge.
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Logistics
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Test Indications:
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Third tier confirmatory testing of positive congenital adrenal hyperplasia (CAH) newborn screens.
As an adjunct to measurement of basal and ACTH-1-24-stimulated 17-hydroxyprogesterone, androstenedione, and other adrenal steroid levels in the diagnosis of atypical or nonclassical cases of CAH.
Carrier detection of CYP21A2 mutations and genetic counseling.
As an adjunct to measurement of amniotic fluid 17-hydroxyprogesterone and androstenedione measurements in the antenatal diagnosis of 21-hydroxylase deficiency.
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Lab Testing Section:
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Anatomic Pathology – Sendouts
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Referred to:
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Mayo Medical Laboratories (MML#: 89081)
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Phone Numbers:
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MIN Lab: 612-813-6280
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STP Lab: 651-220-6550
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Test Availability:
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Daily, 24 hours
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Turnaround Time:
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5 – 11 days
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Special Instructions:
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Include form CYP21A2 Gene Testing Patient Information Sheet with the specimen.
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Specimen
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Specimen Type:
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Whole blood
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Container:
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Lavender top (EDTA) tube
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Draw Volume:
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3 mL (Minimum: 0.2 mL) blood
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Processed Volume:
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Same as Draw Volume
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Collection:
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Routine venipuncture
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Special Processing:
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Lab Staff: Do Not Centrifuge. Specimen should remain in the original collection container. Store and ship at room temperature. Forward promptly.
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Patient Preparation:
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None
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Sample Rejection:
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Mislabeled or unlabeled specimens; specimens other than EDTA whole blood; frozen specimens
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Interpretive
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Reference Range:
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An interpretive report will be provided.
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Limitations:
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Because of the complexity of the genetic structure of the CYP21A2 locus, and the possibility that a patient’s congenital adrenal hyperplasia (CAH) may be due to other gene defects, genetic testing results should be correlated carefully with clinical and biochemical data.
This testing strategy is superior to approaches previously used, but may still miss some complex and large-scale genetic rearrangements or deletions, as well s genetic changes in far upstream or downstream gene-regulatory elements that impair CYP21A2 gene expression. This can lead to false-negative test results.
Rare polymorphisms in primer binding sites can lead to selective allelic drop-out, which can lead to false-negative or false-positive diagnosis.
Patients without genetic evidence for disease-causing CYP21A2 genetic changes may still suffer from CAH, but due to a different enzyme defect. Additional and expanded biochemical steroid profiling is, therefore, recommended if the clinical picture is strongly suggestive of CAH.
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Methodology:
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Polymerase Chain Reaction (PCR), DNA sequencing
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References:
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Mayo Medical Laboratories April 2011
Phone: 1-800-533-1710
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Updates:
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1/13/2011: CPT update
4/5/2011: Test moved from Athena Diagnostics to Mayo Medical Laboratories.
2/5/2013: CPT update
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