Table 2. Summary of Laboratory Tests to Assess Vitamin B12 Deficiency.

Laboratory Test	Rationale for Test	Advantages	Disadvantages
Cobalamin	Decreases in vitamin B12 deficiency	Easily accessible test $10–$15 per test (in Ontario) Most commonly used test with the most literature about abnormal cut-offs	Sensitivity and specificity is unclear
Methymalonic acida	Increases with vitamin B12 deficiency	High sensitivity	Questionable specificity ~$105 per test in Ontario (uninsured)
Total homocysteinea	Increases with vitamin B12 deficiency	High sensitivity	Low specificity influenced by lifestyle factors (smoking, alcohol consumption, coffee consumption) ~$65 per test in Ontario (uninsured)
Holotranscobalamina	Decreases with vitamin B12 deficiency Newer test, clinical utility unclear	High sensitivity	Specificity unclear

^aThese laboratory tests are uninsured in community laboratories in Ontario.

Source: Hvas and Nexo. (16)