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. 2013 Aug;20(8):1203–1212. doi: 10.1128/CVI.00089-13

Table 1.

Cutoffs recommended by manufacturers for interpretation of serologic values

System Assay (unit)a Negative/low Gray zone Positive/high
Vidas IgG (IU/ml) <4.0 4.0 ≤ x < 8.0 ≥8.0
IgM (index) <0.55 0.55 ≤ x < 0.65 ≥0.65
IgG avidity (index) <0. 2 0.2 ≤ x < 0.3 ≥0.3
Architect IgG (IU/ml) <1.6 1.6 ≤ x < 3.0 ≥3.0
IgM (index) <0.50 0.50 ≤ x < 0.60 ≥0.60
IgG avidity (%) <50.0 50.0 ≤ x < 60.0 ≥60.0
Liaison IgG (UI/ml) <7.2 7.2 ≤ x < 8.8 ≥8.8
IgM (AU/ml) <6.0 6.0 ≤ x < 8.0 ≥8.0
IgG avidity (index) <0.30 0.30 ≤ x < 0.40 ≥0.40
a

For all three IgG avidity assays, a high avidity value allows exclusion of a primary infection dating back less than 4 months. IU, international unit; AU, arbitrary unit.