Methaemoglobin
PLEASE NOTE THAT BLOOD GAS ANALYSIS IS NOT AVAILABLE FROM THE BLOOD SCIENCES LABORATORY
Specimen
Heparinised blood in a commercial blood gas syringe.
Test Usage
Methaemoglobin is present in erythrocytes (less than 0.5 g/dl) where t is formed during glycolysis and constantly reconverted to haemoglobin. Increased amounts cause a shift in the oxygen dissociation curve to the left so tissues receive less oxygen.
Methaemoglobin is liberated from cells during intravascular haemolysis and can be filtered by the kidneys in the same way as haemoglobin (HB) which in turn can be converted to Methaemoglobin after it has passed into the urine.
Pathological increases in Methaemoglobin may be due to drugs that enhance its synthesis or depress its conversion to Hb.
A reduced conversion of Methaemoglobin to Hb also occurs in congenital methaemoglobinia
Epidemiology
- Incidence – not common; type II is sporadic
- Ethnicity – type I is endemic in Asthabascan and Navajo native Americans, Yakuts, and Siberian natives; sporadic in other races
Genetics
- Autosomal dominant disorder
Mutations of α globin genes; lifelong phenotype of cyanosis
Mutations of β globin genes; phenotype of cyanosis after 2-6 months of age
Mutations of γ globin genes; phenotype of cyanosis during first 2-6 months of age
- Autosomal recessive disorder
Homozygous or compound heterozygous mutations of cytochrome b5 reductase
Type I – affects mature red blood cells only
Type II – affects all cell types
Clinical Presentation
- Type I – anaemia, gray skin, cyanosis; no reduced life expectancy
Tolerate levels of M-haemoglobins up to 40%
- Type II – manifests as intellectual disability and development delay; reduced life expectancy
Availability
Local test
Turnaround Time
1 day
Cannot be added on to an existing request
Accreditation
Please note this test is not UKAS accredited
Specimen Labelling Procedure
