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Clinical and Diagnostic Laboratory Immunology, July 2002, p. 824-827, Vol. 9, No. 4
1071-412X/02/$04.00+0     DOI: 10.1128/CDLI.9.4.824-827.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Validation of an In-House Assay for Cytomegalovirus Immunoglobulin G (CMV IgG) Avidity and Relationship of Avidity to CMV IgM Levels

Harry E. Prince1* and Amy L. Leber2

Focus Technologies, Cypress,1 Quest Diagnostics, San Juan Capistrano, California2

Received 18 January 2002/ Accepted 7 March 2002

Measurement of cytomegalovirus (CMV)-specific immunoglobulin G (IgG) avidity has proven to be a powerful tool for distinguishing primary from nonprimary CMV infection. An in-house enzyme-linked immunosorbent assay (ELISA) for measuring CMV IgG avidity was validated using 84 sera from pregnant women who had recently seroconverted following primary CMV infection and 74 sera from individuals with past CMV infection (IgG-positive and IgM-negative profile). Of the 84 sera from pregnant women, 73 sera were collected within 120 days of the last IgG-negative sample, and 72 of these 73 sera (99%) exhibited an avidity index (AI) of <50%. In contrast, 71 of 74 (96%) sera from individuals with past CMV infection exhibited CMV AI values of >60%. Thus, low avidity in the in-house ELISA was defined as an AI of <=50%, whereas high avidity was defined as an AI of >=60%. In additional studies, the relationship between CMV IgG avidity and CMV IgM levels was examined using 64 CMV IgG-positive sera (time since seroconversion unknown) exhibiting equivocal or positive results in a CMV IgM capture ELISA (Diamedix). Of these 64 sera, 29 exhibited IgM index values of >=3.0, and 27 of these 29 (93%) exhibited low IgG avidity. A similar trend was observed when a subset of these 64 sera (n = 48) was tested in another CMV IgM capture ELISA (Trinity); of 18 sera with IgM index values of >=3.0, 17 (94%) exhibited low IgG avidity. These findings demonstrate the validity of an in-house ELISA for CMV IgG avidity and further show that strong reactivity of CMV IgG-positive sera in either of two CMV IgM capture assays is a reliable indicator of low CMV IgG avidity, and thus, recent CMV infection.

* Corresponding author. Mailing address: Focus Technologies, 5785 Corporate Ave., Cypress, CA 90630. Phone: (714) 220-1900. Fax: (714) 484-1296. E-mail: hprince{at}focusanswers.com.

Clinical and Diagnostic Laboratory Immunology, July 2002, p. 824-827, Vol. 9, No. 4
1071-412X/02/$04.00+0     DOI: 10.1128/CDLI.9.4.824-827.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Fox, J. L., Hazell, S. L., Tobler, L. H., Busch, M. P. (2006). Immunoglobulin G Avidity in Differentiation between Early and Late Antibody Responses to West Nile Virus. CVI 13: 33-36 [Abstract] [Full Text]  
  • Prince, H. E., Lape-Nixon, M., Busch, M. P., Tobler, L. H., Foster, G. A., Stramer, S. L. (2005). Utilization of Follow-Up Specimens from Viremic Blood Donors To Assess the Value of West Nile Virus Immunoglobulin G Avidity as an Indicator of Recent Infection. CVI 12: 1123-1126 [Abstract] [Full Text]  


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