Elevated methylmalonic acid and total homocysteine levels show high prevalence of vitamin B12 deficiency after gastric surgery. - Sumner AE; Chin MM; Abrahm JL; Berry GT; Gracely EJ; Allen RH; Stabler SP; Sumner, A E; Chin, M M; Abrahm, J L; Berry, G T; Gracely, E J; et al. (Annals of Internal Medicine, 1996)