Asthma (ADRB2 Genotype Assay for R16G)
- Synonyms: beta ADRENERGIC, BETA-2-ADRENERGIC RECEPTOR
- LIS Mnemonic: MBADRB2
Collect
Collect whole blood in a purple top (EDTA) tube.
Volume Required
5 mls
Minimum Required
3 mls
Transport
Refrigerate sample until shipment. Send the sample at room temperature with overnight delivery for receipt Monday through Friday within 24 hours of collection.
Stability
Whole blood can be refrigerated until shipment.
Unacceptable conditions
Heparinized specimens, severely hemolyzed specimens, frozen, clotted or possibly commingled specimens, blood in non-sterile or leaky containers, mislabeled or inappropriately labeled specimens.
Specimen Handling
Do not heat, freeze or centrifuge blood before shipment. Refrigerate sample until shipment.
Days Performed
Mon - Fri 9:00am to 4:00pm
Reported
10 days
CPT
81401
Disease Information
Clinical Features:
Clinical indications for ADBR2 genotype analysis in asthma patients includes active asthma requiring inhaled ß-adrenergic agonists (ie, albuterol, isoetharine, metaproterenol, pirbuterol, and terbutaline) and /or an apparent decrease in effectiveness of these drugs for controlling symptoms.
Molecular Genetics:
The ADRB2 gene is located on chromosome 5p31-q32. The mutation is a single nucleotide polymorphism (SNP) at nucleotide 46 (c.46G>A). This SNP has allele frequencies of 0.324 (for the A allele) and 0.676 (for the G allele). The ADRB2 gene encodes the beta 2-adrenergic receptor which is a member of the G protein-coupled receptor super family. A polymorphism at codon 16 of the ADRB2 gene has been associated with altered airway response to regularly inhaled albuterol in mild asthmatics. This SNP results in a codon for etiher arginine or glycine at amino acid position 16. The Arg/Arg genotype has been associated with a decrease in peak expiratory flow compared to patients with either the Gly/Gly or Gly/Arg genotypes with regular use of the beta agonist albuterol.
Test Methods:
We detect the c.46G>A change using an allelic discrimination assay. The patient’s sample is compared to homozygous, heterozygous, and known normal controls.
Detection Rate:
The detection rate for allelic discrimination is 100% of ADRB2 genotypes at nucleotide 46.
Results:
Test results with interpretation will be mailed and/or faxed to the referring physician or send out lab following completion of the test. Additional reports will be provided as requested.
Utility:
The clinical utility of the assay is in better management of asthmatic patients (ie, altering the frequency with which drugs are administered or switching from one class of drugs to another. The results of this assay, however, should not be used as the sole or major determinant in managing patient care.
Remarks
Whole blood in EDTA purple top tubes is the preferred sample. High molecular weight genomic DNA, cheek epithelial cells, or other samples containing DNA may be acceptable. Contact the laboratory for specific instructions regarding such samples before sending the sample.
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