Table 3: Vitamin B12 levels, Methylmalonic acid levels, and vitamin B12 deficiency.

RA (n = 45) AITD (n = 36) Control (n = 44) 'p' value
Vitamin B12 levels (pg/mL) 726.3 ± 392.9 606.8 ± 281.8 655.8 ± 342.7 0.297
Methylmalonic acid levels (nmol/L) 202.4 ± 79.3 216.1 ± 125.1 190.5 ± 118.4 0.575
Vitamin B12 < 200 pg/mL (Prevalence %) 0 (0%) 0 (0%) 1 (2.3%) NS
Vitamin B12 < 350 pg/mL (Prevalence %) 3 (6.7%) 6 (16.7%) 4 (9.1%) NS
Vitamin B12 < 220 pmol/L AND Methylmalonic
acid > 378 nmol/L* (Prevalence %)
0 (0%) 1 (2.8%) 1 (2.3%) NS

Key: *Marks PW, et al. NEJM. 2004; 351: 1338.

The one subject in the control arm with a serum vitamin B12 level less than 200 pg/mL was the same subject who also had a serum vitamin B12 < 220 pmol/L and Methylmalonic acid > 378 nmol/L

To convert values for serum vitamin B12 from picograms per milliliter to picomoles per liter, multiply by 0.7378.