The ESEN (European Sero-Epidemiology Network) project was established to harmonize the
seroepidemiology of five vaccine preventable infections including measles, mumps and rubella
in eight European countries. This involved achieving comparability both in the assay results
from testing in different centres and also sampling methodology. Standardization of enzyme
immunoassay results was achieved through the development of common panels of sera by
designated reference centres. The panels were tested at the reference laboratory and then
distributed to each participating laboratory for testing using their routine methods.
Standardization equations were calculated by regressing the quantitative results against those of
the reference laboratory. Our study found large differences in unitage between participants,
despite all using an EIA method standardized against an international or local standard.
Moreover, our methodology adjusted for this difference. These standardization equations will
be used to convert the results of main serosurvey testing into the reference country unitage to
ensure inter-country comparability.