Re-evaluation of the VIDAS(®) cytomegalovirus (CMV) IgG avidity assay: determination of new cut-off values based on the study of kinetics of CMV-IgG maturation.

BACKGROUND

In case of cytomegalovirus (CMV) infection, differentiation between primary and non-primary CMV infection can be of major importance for the correct management of pregnant women or immunocompromised patients. Besides CMV-IgM and IgG, CMV-IgG avidity measurement is now commonly used to distinguish primary from non-primary infection.

OBJECTIVE

To re-evaluate the performance of the VIDAS CMV-IgG avidity assay in comparison with 2 other techniques (Architect Abbott and Liaison DiaSorin) and to study the kinetics of CMV-IgG avidity maturation.

STUDY DESIGN

A panel of 135 sequential samples collected from 31 patients with a proven primary infection (attested by very recent CMV-IgG seroconversion) was tested with VIDAS, Liaison and Architect CMV-IgG avidity assays. Moreover, 235 routinely collected samples, CMV-IgG and CMV-IgM positive, were analyzed with Liaison, VIDAS and an in-house CMV-IgG avidity assay.

RESULTS AND CONCLUSIONS

The analysis of all the data allowed suggesting new VIDAS cut-off values of 0.40 for low avidity and 0.65 for high avidity, which significantly increase the test performance and enable better patient managements. Using these VIDAS new cut-off values, all of the 31 primary infections were correctly dated. Comparatively, 25 out of 31 were correctly dated with the Architect assay and 29 out of 31 with the Liaison assay. We also demonstrated that the VIDAS CMV-IgG avidity assay allows observing correctly the maturation of CMV-IgG avidity, which could be useful as an additional parameter for diagnosis of a recent CMV infection.