I am currently working on SARS-CoV-2 antibody level ELISA kit. And the protocols only mention about converting the final concentration to International Unit (IU/mL), which is standardized by WHO. However, nowadays there seems to be another unit, which is Binding Antibody Unit (BAU/mL), which is described by WHO as a better option for describing ELISA results. Does anyone know, how to convert the ready values in IU/mL to BAU/mL?
Hello Muhaimin Shukri
The quantity of unit in the tested sample is quantified in the unit specific for each assay (either U/ml or AU/ml), and converted to binding antibody units (BAU)/ml according to manufacturer's information regarding the WHO international standard which is reagent specific. Samples with values over the cut-off value can be diluted using reagents supplied by the manufacturer and analyzed again. This will allow the extension of the dynamic range of analysis.
The manufacturer usually provides the following:
the cut-off value in AU/mL,
the conversion factor to obtain BAU/mL,
the cut-off value in BAU/mL and
the linearity range in AU/mL
You can refer to the articles below for detailed explanation. They will be helpful.
Article The WHO International Standard for COVID-19 serological test...
https://www.medrxiv.org/content/10.1101/2021.04.29.21256246v1.full.pdf
Best.
Article WHO International Standard for anti-SARS-CoV-2 immunoglobulin
Dear Dr Muhaimin Shukri,
I invite you to read this document:
https://www.testlinecd.com/file/2572/COVID-19_BAU_EIA_EN.pdf
Best regards,
Pr Hambaba