Serum vitamin B12 and folate were analysed by Access Immunoassay Systems 33000 and A98032, respectively (Beckman Coulter, Brea, CA, USA). Homocysteine was analysed with the ARCHITECT Homocysteine Assay 1L71 (Abbott, Wiesbaden, Germany). 25-OH-vitamin D was measured with the 25-Hydroxyvitamin D 125I RIA Kit (68100E; DiaSorin Inc, Stillwater, MN, USA). Serum albumin and total protein were measured with the ALB2: ACN 8413 and TP2: ACN 8678 in vitro tests, respectively, on a cobas® c 701/702 analyser (Roche Diagnostics, Mannheim, Germany).
Vitamin B12 deficiency and elevated homocysteine (hyperhomocysteinaemia) were defined as <150 pmol/l [17 (link), 18 (link), 33 (link), 34 (link)] and ≥15.0 μmol/l, respectively [35 (link)]. Folate deficiency was defined as <13.5 nmol/l based on the laboratory’s chosen definition, vitamin D deficiency as <49.9 nmol/l and vitamin D insufficiency as ≥49.9 nmol/l and <74.1 nmol/l [13 (link)].
Vitamin B12 deficiency and elevated homocysteine (hyperhomocysteinaemia) were defined as <150 pmol/l [17 (link), 18 (link), 33 (link), 34 (link)] and ≥15.0 μmol/l, respectively [35 (link)]. Folate deficiency was defined as <13.5 nmol/l based on the laboratory’s chosen definition, vitamin D deficiency as <49.9 nmol/l and vitamin D insufficiency as ≥49.9 nmol/l and <74.1 nmol/l [13 (link)].