The European Sero-Epidemiology Network: standardizing the enzyme immunoassay results for measles, mumps and rubella

Abstract

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.

The seroepidemiology of measles in Western Europe

“…As detailed in a paper describing the standardization process, these values are at variance with the unitages produced by other EIAs [9], thus the results reported in this paper may differ slightly from percentages reported elsewhere by individual countries.…”

“…This has been described in detail previously [9]. Briefly, the process involved the distribution of a panel of 150 negative, low positive and positive sera for measles antibody by a reference laboratory (Statens Serum Institut, Copenhagen, Denmark) to the national laboratory in each participating country.…”

Standardization of measles, mumps and rubella assays to enable comparisons of seroprevalence data across 21 European countries and Australia

“…The remaining 24 samples of the panel were prepared using the 2nd International Standard for anti-measles serum, human (66/202), the 2nd British Standard for anti-rubella serum, human (67/182) and the 2nd Working Standard for anti-mumps serum (3/2000) and seven dilutions of these standards. The latter standard was prepared in the RL using a blood donation of a patient with acute mumps and it provided 600 U after calibration against the 1st mumps Working Standard [11]. The sera of the reference panel were tested by the RL four times in 2001 using commercial EIAs (Enzygnost, Dade Behring, Germany), which provide quantitative antibody values for measles and rubella in IU/ml and for mumps in titres.…”

The European Sero-Epidemiology Network 2 (ESEN2): standardization of assay results for hepatitis A virus (HAV) to enable comparisons of seroprevalence data across 15 countries

“…This methodology has been applied successfully for various vaccine-preventable infections during the ESEN projects, i.e. : (i) measles, mumps, rubella [16,20] ; (ii) pertussis [17] ; (iii) diphtheria [19]) ; (iv) VZV [18] ; and (v) HBV [21]. The present collaborative work describes the development of a standardization procedure that allows for direct comparisons of HAV seroprevalence data generated at 15 European laboratories.…”

“…However, inter-laboratory variation, even when using the same EIA and international standards, is a well-recognized problem [15][16][17][18][19][20][21]; accordingly, differences mostly in sensitivity, but also in specificity, have been reported for both commercial and in-house anti-HAV assays [22][23][24][25][26][27][28][29][30][31]. Standardization is a methodological approach that provides a means to overcome this limitation and to ensure the direct comparability of seroepidemiological results obtained during the project [32].…”