title: Detection of acute Toxoplasma gondii infection in early pregnancy by IgG avidity and PCR analysis.
abstract: Acute Toxoplasma gondii infection in early pregnancy carries the risk of transmitting the infection to the fetus with serious sequelae. However, serological testing for IgG/IgM anti-Toxoplasma antibodies may fail to differentiate between a recent and past infection. Two hundred and twenty-four Kuwaiti women in their first trimester were screened for IgG/IgM antibodies by the Vitek Immuno Diagnostic Assay System (VIDAS) and VIDAS IgG-avidity tests. On serological screening, 119 (53.1 %) women were positive for IgG antibodies and 31 (13.8 %) for IgM antibodies. Nine of the IgM-positive and 7 IgM-negative women had low-avidity antibodies. However, the IgG-avidity test detected low-avidity antibodies only in 9 (29 %) of the 31 IgM-positive women, suggesting a recent infection; 19 (61.3 %) women had high-avidity antibodies, indicating that the infection was acquired in the distant past. Based on IgM serology alone, at least 31 IgM-positive women may have been wrongly labelled as having acute Toxoplasma infection thus warranting appropriate therapeutic intervention. All the 19 IgM-positive women with high-avidity antibodies were confirmed negative for Toxoplasma DNA on PCR analysis. Compared with PCR analysis, the VIDAS avidity test was a helpful tool for the diagnosis of recent Toxoplasma infection in IgM-negative women with low-avidity antibodies and IgM-positive women with high-avidity antibodies; the specificity was >85 -100 %. It is concluded that the VIDAS avidity test when used in combination with VIDAS IgG/IgM tests is a valuable assay for the exclusion of ongoing or recently acquired T. gondii infection in pregnant women in their first trimester and that it decreases significantly the necessity for follow-up testing and unnecessary therapeutic intervention.
authors.affiliation: Department of Microbiology, Faculty of Medicine, Kuwait University, PO Box 24923, Safat 13110, Kuwait.
authors.forename: Jamshaid
authors.initials: J
authors.lastname: Iqbal
authors.affiliation: Department of Microbiology, Faculty of Medicine, Kuwait University, PO Box 24923, Safat 13110, Kuwait.
authors.forename: Nabila
authors.initials: N
authors.lastname: Khalid
mesh_terms: D000328:Adult; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood*; D000915:Antibody Affinity; D016054:DNA, Protozoan / Q000097:blood; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007075:Immunoglobulin M / Q000097:blood; D007730:Kuwait; D016133:Polymerase Chain Reaction / Q000379:methods*; D011247:Pregnancy; D015597:Pregnancy Complications, Parasitic / Q000175:diagnosis; D012680:Sensitivity and Specificity; D014122:Toxoplasma / Q000235:genetics* / Q000276:immunology*; D014123:Toxoplasmosis / Q000175:diagnosis*
chemical_list: D000913:Antibodies, Protozoan; D016054:DNA, Protozoan; D007074:Immunoglobulin G; D007075:Immunoglobulin M