International Standard for serum vitamin B12 and serum folate: international collaborative study to evaluate a batch of lyophilised serum for B12 and folate content

Use of IS 03/178 to standardise serum B(12) and folate assays reduced inter-laboratory variability. The World Health Organization (WHO) Expert Committee on Biological Standardisation established 03/178 as the first IS for serum vitamin B(12) and serum folate, with assigned values of 480 pg/mL of vitamin B(12) and 12.1 nmol/L folate when the lyophilised contents of the ampoule are reconstituted with 1 mL of water.