Test Database

Description

A Gerstel Multi Purpose Sampler coupled with liquid chromatography and electrospray ionisation tandem mass spectrometry (LC-ESI-MS/MS) Due to the relocation of the Nutristasis service to the Blackfriars Hub site, this test is not currently accredited by UKAS to ISO15189

Clinical details

The importance of maintaining adequate cellular levels of vitamin B12 is well known and early detection of deficiency is essential to prevent irreversible neurological damage which can also occur in the absence of relatively easy to diagnose - anaemia. Unfortunately an accurate diagnosis of vitamin B12 deficiency is still problematic. The timely detection, and correction, of vitamin B12 deficiency prevents macrocytic anaemia, elevated homocysteine (possible thrombotic risk factor), potentially irreversible peripheral neuropathy, memory loss and other cognitive deficits. Metabolic markers of status include circulatory levels of homocysteine and methylmalonic acid (MMA). Unfortunately, the utility of an elevated plasma homocysteine concentration to indicate impaired methionine synthase function as a consequence of poor vitamin B12 availability (specifically the methyl-cobalamin form) has a co-dependency on the optimal supply of 5-methyltetrahydrofolate. MMA does not share this limitation and its measurement is considered as the gold standard and the most representative marker of metabolic vitamin B12 insufficiency. Vitamin B12 (specifically the adenosyl-cobalamin form) is a cofactor for the methylmalonyl-CoA mutase catalysed conversion of methylmalonyl-CoA to succinyl-CoA. MMA is a by-product of this pathway with no known biological function. In vitamin B12 insufficiency excess of methylmalonyl-CoA is hydrolysed to MMA causing the circulatory concentration of MMA to increase.

Related condition

Vitamin B12 deficiency/ cobalamin disorders, renal disease, hypothyroidism, pernicious anaemia

Reference range

age related: ≤65 yrs 0-280; >65 yrs 0-360

Units

nmol/L

Synonyms

MMA/Vitamin B12 deficiency/ cobalamin disorders

Testing site

Synnovis : Reference Services : Blackfriars Hub

Laboratory

Nutristasis Unit