Elecsys® CMV IgG Avidity

Immunoassay for the qualitative determination of CMV IgG avidity

Elecsys® CMV IgG Avidity
Immunoassay for the qualitative determination of CMV IgG avidity

Cytomegalovirus (CMV) is a herpes virus ubiquitous in humans, and it is the leading infectious cause of congenital malformations.1 Anti-CMV IgG and IgM reactive samples may indicate an acute, recent or reactivated infection.

Since fetal symptomatic congenital infection is mostly due to intrauterine transmission following primary maternal infection, differential diagnosis of primary versus recurrent infection, unspecific IgM or persistence of CMV-specific IgM antibody is crucial for the management of the pregnancy.2 Antibodies produced at an early stage during primary response have lower antigen avidity than those produced at a later stage.2

A low-avidity anti-CMV IgG detected before the 16th – 18th week of pregnancy, together with a positive anti-CMV IgM, is strong evidence of a recent primary infection, whereas a high avidity index during the first 12 – 16 weeks would be considered a good indicator of past infection.2 A high avidity result later in gestation cannot rule out a primary infection at an earlier stage of the pregnancy.2

Elecsys® CMV IgG Avidity

Elecsys® CMV IgG Avidity3

  • Systems

    cobas e 411 analyzer, cobas e 601 / cobas e 602 modules, cobas e 402 / cobas e 801 analytical units

     

  • Testing Time

    2 × 18 minutes in parallel 

  • Test principle

    One-step double antigen sandwich immunoassay (DAGS) under various buffer conditions 

  • Calibration

    2-point

  • Interpretation

    <45.0 Avi % = low avidity
    45.0 – 54.9 Avi % = gray zone
    ≥55.0 Avi % = high avidity 

  • Traceability

    This method has been standardized against a Roche standard (arbitrary units) 

  • Sample material

    Serum collected using standard sampling tubes or tubes containing separating gel. Li-heparin, K2-EDTA and K3-EDTA plasma    

  • Sample volume

    20 + 50 μL cobas e 411 analyzer, cobas e 601 / cobas e 602 modules
    12 + 24 μL cobas e 402 / cobas e 801 analytical units

     

     

     

     

     

     

     

     

     

     

     

     

     

     

  • Onboard stability

    14 days for cobas e 411 analyzer, cobas e 601 / cobas e 602 modules
    16 weeks for cobas e 402 / cobas e 801 analytical units

     

     

     

  • cobas e flow

    cobas e 402 / cobas e 801 analytical units. Automatic dilution, preparation of avidity and reference sample, and calculation of the avidity (Avi%)

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

  • Intermediate precision

    cobas e 411 analyzer: CV 1.9 - 3.8 %
    cobas e 601 / 602 modules: CV 1.9 - 3.4 %
    cobas e 402 / cobas e 801 analytical units: CV 1.5 - 3.2 %

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

  • Agreement with a commercially available method

    96.1 % (n = 77) lower 95 % C.I.: 89.0 %
    93.4 % (n = 106) lower 95 % C.I.: 86.9 % 

  • Analytical specificity

    90.9 % (n = 44) lower 95 % C.I.: 78.3 % 
    100.0 % (n = 51) lower 95 % C.I.: 93.0 % 

References

  1. Van Zuylen WJ, et al. Congenital cytomegalovirus infection: Clinical presentation, epidemiology, diagnosis and prevention. Obstet Med. 2014; 7(4):140–146.
  2. Revello MG, Gerna G. Diagnosis and Management of Human Cytomegalovirus Infection in the Mother, Fetus, and Newborn Infant. Clin Microbiol Rev. 2002; 15(4):680–715.
  3. Elecsys® CMV IgG Avidity (#09342397190, #09342389190) method sheet 2022, V. 2.0 and 1.0.