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 Avidity

  • Systems

    cobas e 411 analyser, cobas e 601 / cobas e 602 modules, cobas e 801 module

  • 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 standardised 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 analyser, cobas e 601 / cobas e 602 modules
    12 + 24 μL cobas e 801 module

  • Onboard stability

    14 days for cobas e 411 analyser, cobas e 601 / cobas e 602 modules
    16 weeks for cobas e 801 module

  • cobas e flow

    cobas e 801 module. Automatic dilution, preparation of avidity and reference sample, and calculation of the avidity (Avi%)

  • Intermediate precision

    cobas e 411 analyser: CV 2.0–3.1 %    
    cobas e 601 / 602 modules: CV 1,5 – 3.8 % 
    cobas e 801 module: CV 1.4 – 6.0 % 

  • 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, W.J. et al. (2014). Obstet Med 7, 140-146.
  2. Revello, M.G. et al. (2002). Clin Microbiol Rev 15, 680-715.3.