| CMV antibodies | IgG avidity | Interpretation | Implications |
| IgM– and IgG– | Not applicable | Uninfected or very early infection | Counsel about behavioral measures to reduce risk of acquiring infection |
| IgM+ and IgG– | Not applicable | May be false positive (90%) due to another virus, autoimmune disease, laboratory methods | Repeat in two weeks |
| IgM+ and IgG+ | Low | Recent infection Seroconversion is diagnostic of primary infection | Counsel about likelihood of fetal infection, possible sequelae, and options for prenatal diagnosis and management |
| IgM+ and IgG+ | High | Past infection versus recurrent infection A significant rise (at least double) in serial IgG titers suggests reactivation or reinfection | Counsel about low risk of fetal infection, but possible sequelae if fetus is infected |
| IgM– and IgG+ | High | Past infection Absence of a significant rise in serial IgG titers suggests absence of reactivation or reinfection | Counsel about low risk of fetal infection and possible sequelae No need for further testing |
| IgM– and IgG+ | Low | Unclear because all validation studies of avidity have been in the setting of true positive IgM |
