Test Code GNANG Hereditary Angioedema Focused Gene Panel, Next-Generation Sequencing, Varies

Ordering Guidance

This test is designed to detect disease-causing variants in the F12, KNG1, and PLG genes and to be utilized for genetic confirmation of a clinical diagnosis of hereditary angioedema with normal C1 inhibitor (HAE with normal C1INH) or factor XII deficiency.

Genetic testing for HAE with normal C1INH should only be considered if there is a documented family history of angioedema that does not respond to chronic, high-dose antihistamine therapy, normal complement studies, normal C1-INH level and function, and no exposure to medications that could cause angioedema, such as angiotensin-converting enzyme inhibitors or nonsteroidal anti-inflammatory drugs.

Genetic testing for factor XII deficiency should only be considered if clinical and family history, initial coagulation screens, or initial activity tests indicate a diagnosis.

This test does not measure complement 4, C1INH antigen, C1INH functional, or factor XII activity levels.

-For assessment of C4, order C4 / Complement C4, Serum.

-For assessment of C1INH antigen, order C1ES / C1 Esterase Inhibitor Antigen, Serum.

-For assessment of functional C1INH , order C1INF / C1 Esterase Inhibitor, Functional, Serum.

-For assessment of factor XII activity, order F_12 / Coagulation Factor XII Activity Assay, Plasma.

Customization of this panel and single gene analysis for any gene present on this panel are available. For more information see CGPH / Custom Gene Panel, Hereditary, Next-Generation Sequencing, Varies.

Targeted testing for familial variants (also called site-specific or known variants testing) is available for the genes on this panel. See FMTT / Familial Variant, Targeted Testing, Varies. To obtain more information about this testing option, call 800-533-1710.

Shipping Instructions

Specimen preferred to arrive within 96 hours of collection.

Necessary Information

Rare Coagulation Disorder Patient Information is required. Testing may proceed without the patient information, however, the information aids in providing a more thorough interpretation. Ordering providers are strongly encouraged to fill out the form and send with the specimen.

Specimen Required

Specimen Type: Whole blood

Patient Preparation: A previous bone marrow transplant from an allogenic donor will interfere with testing. Call 800-533-1710 for instructions for testing patients who have received a bone marrow transplant.

Container/Tube:

Preferred: Lavender top (EDTA)

Acceptable: Yellow top (ACD)

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send whole blood specimen in original tube. Do not aliquot.

Specimen Stability Information: Ambient (preferred) 4 days/Refrigerated

Forms

1. Rare Coagulation Disorder Patient Information (T824) is required.

2. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available:

-Informed Consent for Genetic Testing (T576

-Informed Consent for Genetic Testing (Spanish) (T826)

3. If not ordering electronically, complete, print, and send an Coagulation Test Request (T753) with the specimen.

Secondary ID

619215

Useful For

Evaluating hereditary angioedema (HAE) with normal C1 inhibitor (C1INH) in patients with a suggestive personal or family history

Confirming a diagnosis of HAE with normal C1INH with the identification of a known or suspected disease-causing alteration in the F12, PLG or KNG1 gene

Determining the disease-causing alteration within the F12, PLG or KNG1 gene to delineate the underlying molecular defect in a patient with a laboratory diagnosis of HAE with normal C1INH

Evaluating factor XII deficiency in patients with a suggestive personal or family history

Confirming a factor XII deficiency diagnosis with the identification of known or suspected disease-causing alteration(s) in the F12 gene

Determining the disease-causing alteration(s) within the F12 gene to delineate the underlying molecular defect in a patient with a laboratory diagnosis of factor XII deficiency

Identifying the causative alteration(s) for genetic counseling purposes

Prognosis and risk assessment based on the genotype-phenotype correlations

Carrier testing for close family members of an individual with a diagnosis of factor XII deficiency

This test is not intended for prenatal diagnosis.

Testing Algorithm

The clinical workup for hereditary angioedema (HAE) with normal C1 inhibitor ( C1INH) begins with measurements of serum complement factor 4 (C4), C1 inhibitor (C1-INH) antigen, and C1-INH function.

Genetic testing for HAE with normal C1INH is indicated in patients with:

-A history of recurrent angioedema in the absence of concomitant urticaria or use of a medication known to cause angioedema

-Normal or near-normal C4, C1-INH antigen, and C1-INH function

-Lack of response to high-dose antihistamines

International expert consortia have established testing algorithms and diagnostic guidelines for the identification of HAE with normal C1INH.(1,2)

The clinical workup for factor XII deficiency begins with special coagulation testing for factor XII activity. Order F_12 / Coagulation Factor XII Activity Assay, Plasma.

Genetic testing for factor XII deficiency is indicated if:

-Factor XII activity is less than 55% of normal (Note: reference range may vary depending on the locally established reference range).

-Acquired causes of factor XII deficiency have been excluded (eg, liver disease, nephrotic syndrome, DIC, and hematologic neoplasms)

Special Instructions

Method Name

Sequence Capture and Targeted Next-Generation Sequencing (NGS) followed by Polymerase Chain Reaction (PCR) and Sanger Sequencing

Reporting Name

Hereditary Angioedema Panel, NGS

Specimen Type

Varies

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type	Temperature	Time	Special Container
Varies	Varies

Reject Due To

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Clinical Information

Hereditary angioedema with normal C1 inhibitor (HAE with normal C1INH) is a rare blood and immunologic disorder associated with germline variants in the F12 gene (F12-HAE), PLG gene (PLG-HAE), and KNG1 gene (KNG1-HAE). It is inherited in an autosomal dominant manner with incomplete penetrance.(3,4)

HAE with normal C1INH is characterized by recurrent episodes of severe skin and submucosal swelling, abdominal pain attacks, and upper airway obstruction that does not respond to high-dose antihistamine therapy. Facial and tongue swelling are common. Affected individuals have normal complement studies, normal C1INH antigen and function, and no exposure to medications that could cause angioedema, such as angiotensin-converting-enzyme inhibitors or non-steroidal anti-inflammatory drugs. Estrogen exposure exacerbates disease severity in many patients.(2-6)

Acquired angioedema is associated with B-cell lymphoproliferative disorders in some patients, the presence of autoantibodies to C1-INH, and the use of renin-angiotensin-aldosterone system-blockers.(4)

In addition to HAE with normal C1INH, germline variants in the F12 gene are associated with autosomal recessive factor XII deficiency. While this rare blood disorder is characterized by prolonged activated partial thromboplastin time and reduced factor XII activity, it is rarely associated with an excessive bleeding tendency or abnormal bleeding during trauma or surgery. Individuals with factor XII deficiency are generally asymptomatic.(7)

Causes of acquired (nongenetic) factor XII deficiency should be excluded prior to genetic testing, including liver disease, nephrotic syndrome, and chronic granulocytic leukemia.

Reference Values

An interpretive report will be provided.

Interpretation

All detected variants are evaluated according to American College of Medical Genetics and Genomics recommendations.(8) Variants are classified based on known, predicted, or possible pathogenicity and reported with interpretive comments detailing their potential or known significance.

Method Description

Next-generation sequencing (NGS) and/or Sanger sequencing are performed to test for the presence of variants in coding regions and intron/exon boundaries of the F12, KNG1, and PLG genes, as well as some other regions that have known disease-causing variants. The human genome reference GRCh37/hg19 build was used for sequence read alignment. At least 99% of the bases are covered at a read depth over 30X. Sensitivity is estimated at above 99% for single nucleotide variants, above 94% for deletions-insertions (delins) less than 40 base pairs (bp), above 95% for deletions up to 75 bp, and insertions up to 47 bp. NGS and/or a polymerase chain reaction-based quantitative method is performed to test for the presence of deletions and duplications in the F12, KNG1, and PLG genes.

There may be regions of genes that cannot be effectively evaluated by sequencing or deletion and duplication analysis as a result of technical limitations of the assay, including regions of homology, high guanine-cytosine (GC) content, and repetitive sequences. See Targeted Genes and Methodology Details for Hereditary Angioedema Focused Gene Panel and Methodology Details for details regarding the targeted genes analyzed for each test and specific gene regions not routinely covered.(Unpublished Mayo method)

The reference transcript for F12 is NM_000505.3, KNG1 is NM_001102416.3, and PLG is NM_000301.3. Reference transcript numbers may be updated due to transcript re-versioning. Always refer to the final patient report for gene transcript information referenced at the time of testing. Confirmation of select reportable variants may be performed by alternate methodologies based on internal laboratory criteria.

Day(s) Performed