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Test ID FFRBS Friedreich Ataxia, Frataxin, Quantitative, Blood Spot

Reporting Name

Frataxin, Quant, BS

Useful For

Diagnosing individuals with Friedreich ataxia in blood spot specimens

 

Monitoring frataxin levels in patients with Friedreich ataxia

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Whole blood


Necessary Information


Provide a reason for referral with each specimen.



Specimen Required


Supplies: Card-Blood Spot Collection (Filter Paper) (T493)

Container/Tube:

Preferred: Blood spot collection card (T493)

Acceptable: Ahlstrom 226 Filter Paper and Whatman Protein Saver 903 Paper

Specimen Volume: 2 blood spots

Collection Instructions:

1. An alternative blood collection option for a patient >1 year of age is fingerstick.

2. Let blood dry on the filter paper at ambient temperature in a horizontal position for 3 hours.

3. Do not expose specimen to heat or direct sunlight.

4. Do not stack wet specimens.

5. Keep specimen dry.

Additional Information:

1. For collection instructions in Spanish, see Blood Spot Collection Card-Spanish Instructions (T777) in Special Instructions.

2. For collection instructions in Chinese, see Blood Spot Collection Card-Chinese Instructions (T800) in Special Instructions.


Specimen Minimum Volume

1 blood spot

Specimen Stability Information

Specimen Type Temperature Time
Whole blood Ambient (preferred) 30 days
  Frozen  30 days
  Refrigerated  30 days

Reference Values

Pediatric (<18 years) normal frataxin: ≥15 ng/mL

Adults (≥18 years) normal frataxin: ≥21 ng/mL

Day(s) and Time(s) Performed

Alternating Fridays

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

83520

LOINC Code Information

Test ID Test Order Name Order LOINC Value
FFRBS Frataxin, Quant, BS 80980-6

 

Result ID Test Result Name Result LOINC Value
32249 Reason for Referral 42349-1
32250 Method 49549-9
32251 Frataxin 80980-6
32252 Interpretation 59462-2

Clinical Information

Friedreich ataxia (FA) is an autosomal recessive disease affecting approximately 1:50,000 Caucasians. The disease is clinically characterized by progressive spasticity, ataxia, dysarthria, absent lower limb reflexes, sensory loss, and scoliosis. Hypertrophic cardiomyopathy is present in approximately two-thirds of patients and is the most frequent cause of premature death in individuals with FA. Although most individuals begin experiencing initial symptoms between 10 and 15 years of age, atypical late-onset forms with initial symptoms presenting after age 25 do occur.

 

FA is caused by mutations in the FXN gene encoding a mitochondrial protein, frataxin. Mutations in this gene lead to a reduced expression of frataxin, which causes the clinical manifestations of the disease. Approximately 98% of individuals with FA have a homozygous expansion of the GAA trinucleotide repeat in intron 1 of FXN. The remaining 2% of FA patients have the trinucleotide expansion on 1 allele and a point mutation or deletion on the second allele. Normal alleles contain between 5 to 33 GAA repeats. Disease-causing alleles typically range from 66 to 1,700 repeats, though the majority of individuals with FA have repeats ranging from 600 to 1,200.

 

Historically, FA has been diagnosed by use of a DNA-based molecular test to detect the presence of the GAA expansion. Unfortunately, testing for the triplet repeat expansion will miss those patients with point mutations or deletions. Moreover, a molecular-based analysis is not able to effectively monitor treatment, is not amenable to multiplexing with other disease analytes, nor can it be efficiently utilized for population screening. In contrast, a protein-based assay measuring concentration of frataxin is suitable for both diagnosis as well as treatment monitoring in individuals with FA.

Interpretation

Normal results (≥15 ng/mL for pediatric and ≥21 ng/mL for adult patients) in properly submitted specimens are not consistent with Friedreich ataxia.

 

For results outside the normal reference range an interpretative comment will be provided.

Cautions

This test is not suitable for carrier detection.

Clinical Reference

1. Deutsch EC, Oglesbee D, Greeley NR, Lynch DR: Usefulness of frataxin immunoassays for the diagnosis of Friedreich ataxia. J Neurol Neurosurg Psychiatry 2014 Sep;85(9):994-1002

2. Babady NE, Carelle N, Wells RD, et al: Advancements in the pathophysiology of Friedreich ataxia and new prospects for treatments. Mol Genet Metab 2007;92:23-35

3. Boehm T, Scheiber-Mojdehkar B, Kluge B, et al: Variations of frataxin protein levels in normal individuals. Neurol Sci 2011 Apr;32(2):327-30 doi: 10.1007/s10072-010-0326-1

Analytic Time

14 days

Reject Due To

Hemolysis

NA

Lipemia

NA

Icterus

NA

Other

Blood spot specimen that shows serum rings or has multiple layers

NY State Approved

Yes

Method Name

Luminex Immunoassay

Highlights

Friedreich ataxia (FA) presents most commonly between 10 to 15 years of age with progressive neurologic changes including spasticity and ataxia.

 

Decreased frataxin protein levels are diagnostic of FA and can be utilized for monitoring known patients.

 

Frataxin protein analysis is a cost-effective and quick method for establishing a diagnosis of FA and will detect rare variants otherwise missed by common molecular-based trinucleotide repeat analysis.

Forms

1. 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 in Special Instructions:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. Biochemical Genetics Patient Information (T602) in Special Instructions

3. If not ordering electronically, complete, print, and send an Inborn Errors of Metabolism Test Request (T798) with the specimen.

Secondary ID

60476