Aid in the diagnosis of cytomegalovirus (CMV) infection during pregnancy after initial testing for CMV IgM and IgG has been performed.
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Serum separator tube (SST).
Separate serum from cells ASAP or within 2 hours of collection. Transfer 0.5 mL serum to an ARUP Standard Transport Tube. (Min: 0.15 mL)
After separation from cells: Ambient: 48 hours; Refrigerated: 2 weeks; Frozen: 1 year
0.50 Index or less: Low Avidity
0.51-0.59 Index: Intermediate Avidity
0.60 Index or greater: High Avidity
Identifying CMV infections in pregnant women during the first trimester is of significant importance for clinical care. Acute infection is typically characterized by increased CMV-specific IgM and IgG antibodies. However, CMV IgM antibodies may persist for several months or even years after initial infection, which limits their utility in the accurate diagnosis of recent CMV infection. CMV IgM antibodies can also be detected during viral reactivation, thus complicating the diagnosis of a recent primary infection. Therefore, measuring IgG antibody avidity to CMV antigens can aid in discriminating recent from prior CMV infections. Index values of 0.5 or less generally indicate recent infection (within the previous 3 to 4 months). However low avidity values cannot exclude the possibility of persistent IgG antibodies with low avidity. Index values of 0.6 or greater indicate an infection occurring more than 3 months prior to testing. Because IgG avidity testing for CMV after the first trimester is not easily interpreted, detection of high avidity CMV IgG antibodies during the first trimester (12 to 16 weeks gestation) helps exclude a diagnosis of an acute CMV infection post-conception.
Laboratory Developed Test (LDT)
|Component Test Code*||Component Chart Name||LOINC|
|2011814||CMV IgG Ab Avidity||52984-2|