Combined indicator of B12 status (cB12)

Description: 
cB12 (combined indicator of B12 status) previously known as “wellness score” is a rigorously derived mathematical model combining all four markers (total B12, holotranscobalamin (holoTC, Active-B12), homocysteine and methylmalonic acid (MMA) which makes adjustments for age and folate status. Serum total B12, holoTC, serum/plasma homocysteine, serum MMA and folate results are normally required to calculate cB12. Formulas using two or three markers are also available.

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: 
cB12 has been suggested as a more reliable indicator of vitamin B12 status than the individual tests. Depending on the cB12 value obtained, B12 status is classified as: elevated, adequate, low, possible B12 deficiency and probable B12 deficiency. The score has been validated against 5000+ patients and the diagnostic cut-points are validated against the clinical outcomes of hemoglobin and cognitive scoring.
Related condition or disease: 
Pernicious anaemia, malabsorption, vitamin B12 deficiency
Reference range: 

< -2.5                probable vitamin B12 deficiency;

-2.5 to -1.5         possible vitamin B12 deficiency;

-1.5 to -0.5         low vitamin B12;  

-0.5 to 1.5          adequate vitamin B12;  

>1.5                   elevated vitamin B12

 

Synonyms or keywords: 
Fedosov score, wellness score, vitamin B12 status assessment
Department: 
Reference Chemistry
Location: 
Blackfriars Hub
Sample type and Volume required: 
1 ml of separated serum (collected into SST tube)* or 1ml of separated serum and 400 ul of separated plasma (collected into EDTA tube*)
Turnaround time: 
10 working days
Special sample instructions: 

*For homocysteine analysis separate serum/plasma within 2 hrs of blood collection.

Criteria for acceptance / rejections of sample
Storage and transport: 
Room temperarture
Contacts:
Nutristasis Unit at Blackfriars Hub
0204 591 0055
Nutristasis@synnovis.co.uk
Reference Chemistry, 1st Floor Blackfriars Hub
Friars Bridge Court
Blackfriars Road
London
SE1 8NZ

Laboratory opening times
Monday - Friday 09.00 - 17.00
For clinical advice or interpretation of results, please contact the laboratory in the first instance.
Laboratory: 
Nutristasis Unit at Blackfriars Hub

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Last updated: 22/10/2025