Background: Determination of Varicella Zoster virus (VZV) immune status in pregnant women without history of chickenpox is important in identifying those who genuinely need VZV immune globulin prophylaxis following significant exposure to chickenpox or shingles. Immune status testing requires highly sensitive and specific immunoassays for timely and accurate results. Objectives: To compare the performance of DiaSorin LIAISON and Biomerieux VIDAS VZV-IgG assays with reference to a VZV-IgG time-resolved fluorescence immunoassay (TRFIA). Study design: A panel of sera collected from 65 pregnant contacts of VZV and 62 individuals tested for VZV immunity was tested in all three assays. Dose-response curves were generated using International Standards W1044 and 90/690. Results: Sensitivity and specificity of VIDAS compared to VZV-TRFIA was 54.5% and 97.9% respectively and for LIAISON compared to VZV-TRFIA was 67% and 100% respectively. Both assays correlated well with TRFIA with R2 correlation coefficients of 0.79 and 0.76 respectively. Dose-response curves showed both Standards behaved in a similar manner in each assay. For VIDAS, the test cut-off value of 0.9 correlated with 275-280 mIU/ml and for LIAISON a cut-off value of 150 mIU/ml correlated with 208-219 mIU/ml. Conclusions: By dose-response data and in comparison with TRFIA, LIAISON is more sensitive and specific than VIDAS.
- Dose-response curves
- Time-resolved fluorescence immunoassay
- Varicella Zoster
- VZV LIAISON and VIDAS assays