Effect of testing for IgG avidity in the diagnosis of Toxoplasma gondii infection in pregnant women: experience in a US reference laboratory.
The usefulness of testing for IgG avidity in association with Toxoplasma gondii was evaluated in a US reference laboratory. European investigators have reported that high-avidity IgG toxoplasma antibodies exclude acute infection in the preceding 3 months. In this US study, 125 serum samples taken from 125 pregnant women in the first trimester were chosen retrospectively, because either the IgM or differential agglutination (AC/HS) test in the Toxoplasma serologic profile suggested or was equivocal for a recently acquired infection. Of 93 (74.4%) serum samples with either positive or equivocal results in the IgM ELISA, 52 (55.9%) had high-avidity antibodies, which suggests that the infection probably was acquired before gestation. Of 87 (69.6%) serum samples with an acute or equivocal result in the AC/HS test, 35 (40.2%) had high-avidity antibodies. Forty women were given spiramycin, to prevent congenital transmission, and 7 (17.5%) had high-avidity antibodies. These findings highlight the value of testing a single serum sample obtained in the first trimester of pregnancy for IgG avidity.
Department of Immunology and Infectious Diseases, Research Institute, Palo Alto Medical Foundation, Ames Bldg., 795 El Camino Real, Palo Alto, CA 94301, USA.
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Liesenfeld
J G
JG
Montoya
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Kinney
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Press
J S
JS
Remington
D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood*; D000915:Antibody Affinity; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D006386:Hemagglutination Tests; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood; D007074:Immunoglobulin G / Q000097:blood*; D007075:Immunoglobulin M / Q000097:blood; D011247:Pregnancy; D015597:Pregnancy Complications, Parasitic / Q000175:diagnosis*; D011261:Pregnancy Trimester, First; D012016:Reference Values; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014122:Toxoplasma / Q000276:immunology; D014123:Toxoplasmosis / Q000175:diagnosis*; D014481:United States
D000913:Antibodies, Protozoan; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D007073:Immunoglobulin E