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Test Code METR1 Cytochrome b5 Reductase Enzyme Activity, Blood


Necessary Information


 



Specimen Required


Collection Container/Tube:

Preferred: Yellow top (ACD)

Acceptable: Lavender top (EDTA)

Specimen Volume: 6 mL

Collection Instructions: Send whole blood specimen in original tube. Do not aliquot.


Useful For

Evaluation of patients with cyanosis

 

Confirming cases of suspected cytochrome b5 reductase (methemoglobin reductase) deficiency

 

Functional studies in families with cytochrome b5 reductase deficiency

Method Name

Kinetic Spectrophotometry (KS)

Reporting Name

Cytochrome b5 Reductase, B

Specimen Type

Whole Blood ACD-B

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole Blood ACD-B Refrigerated 18 days

Reference Values

≥12 months of age: 7.8-13.1 U/g Hb

Reference values have not been established for patients who are younger than 12 months.

Interpretation

Cytochrome b5 reductase (methemoglobin reductase) activity in neonates (0-6 weeks of age) is normally 60% of the normal adult value. Adult values are attained by 2 to 3 months of age.

 

Heterozygotes have results slightly lower than the reference range. Homozygotes demonstrate little to no cytochrome b5 reductase activity and increased levels of methemoglobin.

Clinical Reference

1. Agarwal AM, Prchal JT. Methemoglobinemia and other dyshemoglobinemias. In: Kaushansky K, Lichtman MA, Prchal JT, et al, eds. Williams Hematology. 9th ed. McGraw-Hill; 2016:789-800

2. Percy MJ, Barnes C, Crighton G, et al. Methemoglobin reductase deficiency: Novel mutation is associated with a disease phenotype of intermediate severity. J Pediatr Haematol Oncol. 2012;34:457-460

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

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

LOINC Code Information

Test ID Test Order Name Order LOINC Value
METR1 Cytochrome b5 Reductase, B 32703-1

 

Result ID Test Result Name Result LOINC Value
METRB Cytochrome b5 Reductase, B 32703-1

Day(s) Performed

Performed weekly

Report Available

1 to 6 days

CPT Code Information

82657

Forms

If not ordering electronically, complete, print, and send a Benign Hematology Test Request (T755) with the specimen