Change Of Assay For Serum Folate
With effect from 22nd June 2016, Wellington SCL will be changing to a new assay for serum folate. This change is due to the restandardisation of the existing assay from Roche Diagnostics, to establish traceability to the latest WHO International Standard, WHO IS 03/178.
Based on the information provided by Roche Diagnostics and our own data, the new results generally will be 20% lower than with the current assay, although the effect is mainly seen for results of <23 nmol/L. Individual results may be up to 50% lower, particularly when the folate is at the level of 12 nmol/L or below. Thus, the results from the new assay cannot be directly compared to the existing assay and this should be taken into account when interpreting the results.
The reference interval for serum folate currently in use is based on multiple lines of evidence from international population data and there is no good evidence to support an adjustment with the change of the assay. The existing reference interval for folate is 9-45 nmol/L and 7-9 nmol/L is considered to be borderline. Overall, folate deficiency is uncommon in our population. From our laboratory data, only 5% of results for folate are below 12 nmol/L. The majority of patients will remain in the same category of folate status related to the current interval, despite variations in the folate results with the change of assay.
Dr Carol Siu, Chemical Pathologist
Dr Alwyn D’Souza, Haematologist