Comparison of the LIAISON(®) CMV IgG Avidity II and the VIDAS(®) CMV IgG Avidity II assays for the diagnosis of primary infection in pregnant women.

Background: The accuracy of IgG avidity assays is crucial for the diagnosis of primary CMV infection in pregnancy.
Objective: To compare the performance of the second generation avidity assays LIAISON(®) CMV IgG Avidity II and VIDAS(®) CMV IgG Avidity II for the diagnosis of primary infection in pregnant women.
Study Design: In our laboratory, in sera of pregnant women presenting with positive CMV IgG and positive CMV IgM, the two avidity assays were run in parallel from January 2013 to April 2015.
Results: The results of the 2 avidity assays were analyzed in 280 sera. The correlation between the second generation LIAISON(®) and VIDAS(®) avidity results was significantly higher than between the results of the first generation assays (77% versus 49%, p<0.001). Discrepant results were mainly explained by the difficulty of the VIDAS(®) assay to reach intermediate and high avidity status over time, suggesting the superiority of the LIAISON(®) assay to achieve high avidity levels. In 4 sera from 3 pregnant women (1.4%) with documented primary infection the LIAISON(®) avidity was falsely high. In these cases the level of CMV IgG was low (<50U/mL).
Conclusion: The LIAISON(®) CMV IgG Avidity II assay reached more rapidly higher avidity status than the VIDAS(®) CMV IgG Avidity II. However, with the LIAISON(®) CMV IgG Avidity II, we identified rare sera with high positive avidity values in documented recent seroconversion. The advantages and drawbacks of each assay must be known for a sound interpretation of the results.
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