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Test ID MET Methemoglobin and Sulfhemoglobin, Blood

Reporting Name

Methemoglobin and Sulfhemoglobin, B

Useful For

Diagnosing methemoglobinemia and sulfhemoglobinemia

 

Identifying cyanosis due to other causes, such as congenital heart disease

Profile Information

Test ID Reporting Name Available Separately Always Performed
METH Methemoglobin, B No Yes
SULF Sulfhemoglobin, B No Yes

Specimen Type

Whole Blood EDTA


Specimen Required


Specimen must arrive within 72 hours of draw.

 

Container/Tube: Lavender top (EDTA)

Specimen Volume: Full tube

Additional Information: Patient's age is required.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
Whole Blood EDTA Refrigerated 72 hours

Reference Values

METHEMOGLOBIN

0-11 months: not established

≥1 year: 0.0-1.5% of total hemoglobin

 

SULFHEMOGLOBIN

0-11 months: not established

≥1 year: 0.0-0.4% of total hemoglobin

Day(s) and Time(s) Performed

Monday through Saturday; Continuously

Test Classification

See Individual Test IDs

CPT Code Information

83050-Methemoglobin

83060-Sulfhemoglobin

LOINC Code Information

Test ID Test Order Name Order LOINC Value
MET Methemoglobin and Sulfhemoglobin, B In Process

 

Result ID Test Result Name Result LOINC Value
8268 Methemoglobin, B 2614-6
8272 Sulfhemoglobin, B 4685-4

Clinical Information

Methemoglobin:

When iron in hemoglobin is oxidized from the normal divalent state to a trivalent state, the resulting brownish pigment is methemoglobin. Methemoglobin cannot combine reversibly with oxygen and is associated with cyanosis.

 

Methemoglobinemia, with or without sulfhemoglobinemia, is most commonly encountered as a result of administration of medications such as phenacetin, phenazopyridine, sulfonamides, local anesthetics, dapsone, or following ingestion of nitrites or nitrates. Congenital methemoglobinemias are rare. They are either due to:

-Deficiency of methemoglobin reductase (also called cytochrome B5 reductase or diaphorase) in erythrocytes, an autosomal recessive disorder.

-One of several intrinsic structural disorders of hemoglobin, called methemoglobin-M, all of which are inherited in the autosomal dominant mode.

 

Methemoglobinemia responds to treatment with methylene blue or ascorbic acid.

 

Sulfhemoglobin:

Sulfhemoglobin cannot combine with oxygen. Sulfhemoglobinemia is associated with cyanosis and often accompanies drug-induced methemoglobinemia. Sulfhemoglobinemia can be due to exposure to trinitrotoluene or zinc ethylene bisdithiocarbamate (a fungicide), or by ingestion of therapeutic doses of flutamide.

 

In contrast to methemoglobinemia, sulfhemoglobinemia persists until the erythrocytes containing it are destroyed. Therefore, blood level of sulfhemoglobin declines gradually over a period of weeks.

 

Patients with sulfhemoglobinemia often also have methemoglobinemia. There is no specific treatment for sulfhemoglobinemia. Therapy is directed at reversing the methemoglobinemia, if present.

Interpretation

In congenital methemoglobinemia, the methemoglobinemia concentration in blood is about 15% to 20% of total hemoglobin. Such patients are mildly cyanotic and asymptomatic.

 

In acquired (toxic) methemoglobinemia, the concentration may be much higher. Symptoms may be severe when methemoglobin is >40% of hemoglobin. Very high concentrations (>70%) may be fatal.

Clinical Reference

Beutler E: Methemoglobinemia and other causes of cyanosis. In Hematology. Sixth edition. Edited by WJ Williams, E Beutler, AJ Erslev, MA Lichtman. New York, McGraw-Hill Book Company, 2001, pp 611-614

Analytic Time

Same day/1 day

Method Name

Spectrophotometry (SP)