title: An International Standard for whole blood folate: evaluation of a lyophilised haemolysate in an international collaborative study.
abstract: Folate measurements, particularly for whole blood, show wide inter-laboratory and inter-methodology variability. This variability appears to be due in part to the lack of internationally accepted reference materials. A whole blood haemolysate, lyophilised in ampoules and designated 95/528, was therefore evaluated by 15 laboratories in five countries for its suitability as an International Standard (IS) for whole blood folate. The preparation was assayed using a variety of microbiological and protein-binding methodologies against local standards and calibrators. A consensus folate content was assigned to 95/528. The inclusion of three whole blood samples in the study with widely differing folate levels demonstrated a considerable reduction in inter-laboratory variability when the folate content of the samples was determined relative to the proposed IS 95/528 rather than to laboratories' local standards and calibrators. Accelerated degradation studies indicated that the folate content of 95/528 is stable when stored at -20 degrees C. On the basis of the results presented here, the World Health Organization Expert Committee on Biological Standardization established 95/528 as an IS for whole blood folate.
authors.affiliation: Division of Haematology, National Institute for Biological Standards and Control, Potters Bar, Hertfordshire, UK. sthorpe@nibsc.ac.uk
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Thorpe
authors.forename: Dawn
authors.initials: D
authors.lastname: Sands
authors.forename: Alan B
authors.initials: AB
authors.lastname: Heath
authors.forename: Malcolm S
authors.initials: MS
authors.lastname: Hamilton
authors.forename: Sheena
authors.initials: S
authors.lastname: Blackmore
authors.forename: Trevor
authors.initials: T
authors.lastname: Barrowcliffe
mesh_terms: D002498:Centrifugation; D016001:Confidence Intervals; D003627:Data Interpretation, Statistical; D005492:Folic Acid / Q000097:blood* / Q000592:standards*; D005612:Freeze Drying; D005615:Freezing; D006461:Hemolysis; D006801:Humans; D012015:Reference Standards; D015203:Reproducibility of Results; D013696:Temperature; D014944:World Health Organization
chemical_list: D005492:Folic Acid