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Journal of Clinical Microbiology, October 2004, p. 4627-4631, Vol. 42, No. 10
0095-1137/04/$08.00+0     DOI: 10.1128/JCM.42.10.4627-4631.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Evaluation of the Immunoglobulin G Avidity Test for Diagnosis of Toxoplasmic Lymphadenopathy

Jose G. Montoya,^1,2* Heather B. Huffman,¹ and J. S. Remington^1,2

Department of Immunology and Infectious Diseases, Research Institute, Palo Alto Medical Foundation, Palo Alto,¹ Department of Medicine, Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, California²

Received 12 April 2004/ Returned for modification 8 June 2004/ Accepted 21 June 2004

Toxoplasmic lymphadenopathy (TL) is the most common clinical manifestation of acute acquired toxoplasma infection in normal individuals. The diagnosis is established by serologic methods and lymph node biopsy. Recently, tests for avidity of toxoplasma immunoglobulin G (IgG) antibodies have been introduced to help discriminate between recently acquired and distant infection with the parasite. We studied an avidity test to define the usefulness of this method and to determine the evolution of the IgG avidity in TL. Seventy-three consecutive patients diagnosed as having TL were studied. IgG avidity test titers were noted to be time dependent from the clinical onset of lymphadenopathy. Low IgG avidity test results were observed in patients who had developed lymphadenopathy from <1 month to 17 months prior to the sampling of sera, emphasizing that low IgG avidity test results are not reliable for diagnosis of recently acquired infection. In contrast, high IgG avidity test results were observed only in patients who had developed lymphadenopathy at least 4 months earlier. Thus, a high IgG avidity test result in an individual who has recent onset of lymphadenopathy (e.g., within 2 to 3 months of sera sampling) suggests a cause other than toxoplasmosis. In such cases, further workup is warranted in order to determine the cause of the lymphadenopathy.

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* Corresponding author. Mailing address: Department of Immunology and Infectious Diseases, Research Institute, Palo Alto Medical Foundation, Palo Alto, CA 94301. Phone: (650) 853-6061. Fax: (650) 329-9853. E-mail: samja{at}stanford.edu.

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Journal of Clinical Microbiology, October 2004, p. 4627-4631, Vol. 42, No. 10
0095-1137/04/$08.00+0     DOI: 10.1128/JCM.42.10.4627-4631.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

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