Vitamin B12 deficiency in dialysis patients: risk factors, diagnosis, complications, and treatment: A comprehensive review

Table 1 A summary of the different diagnostic methods for vitamin B12 deficiency in end-stage kidney disease patients, their utility, and cut-off criteria

Diagnostic method	Use in ESKD	Cut-off criteria for deficiency
Serum vitamin B12 level	Often used as a first-line screening test; limited use due to false normal and inactive analogues (functional deficiency)	< 200 pg/mL; levels < 100 pg/mL have 90% specificity for identifying clinically evident deficiency
Methylmalonic acid	More sensitive in ESKD; elevated due to kidney dysfunction	> 0.4 μmol/L
Homocysteine	Elevated in ESKD; affected by vitamin B12 and folate status	> 15 μmol/L
Holotranscobalamin (active-B12)	Promising but requires more research for ESKD specific cut-offs	< 50 μmol/L
Neutrophil hypersegmentation	Rarely used; not sensitive for mild deficiency	Presence of > 5% neutrophils with ≥ 5 lobes
Macrocytosis (MCV)	May be present but not specific; affected by other factors in ESKD	MCV > 100 fL

MCV: Mean corpuscular volume; ESKD: End-stage kidney disease.