Comparison of IIF, ELISA and IgG avidity tests for the detection of anti-Toxoplasma antibodies in single serum sample from pregnant women.

A valid estimate of test efficiency is needed to choose adequate screening and detecting strategies in diagnosis of acute toxoplasmosis. Therefore, in the present study we evaluated the efficiency of diagnostic laboratory methods to detect anti-toxoplasma antibodies in single serum samples of pregnant women by indirect immunofluorescence test (IIF), enzyme-linked immunosorbent assay (ELISA) and IgG avidity tests in north-western Iran. In an analytical-descriptive study, during March 2010 to April 2013, 391 pregnant women aged 21 to 35 years who were referred by gynaecologists or infectious disease specialists for anti-toxoplasma antibody evaluation were studied. A peripheral blood sample was collected from individuals and serum was prepared immediately for anti-toxoplasma antibody evaluation by IIF, ELISA and IgG avidity tests. ELISA and IgG avidity tests were used as gold standard. Evaluation of anti-toxoplasma antibodies by IIF revealed that 280 cases (71.61%) were seropositive and 111 (28.38%) seronegative, while evaluation by ELISA revealed that 267 cases (68.28%) were seropositive and 124 (31.70%) seronegative; 65 (16.62%) were IgM positive by both IIF and ELISA tests. There were 45 (69.23%) and 7 (10.76%) IgM positive suspected cases respectively in IIF and ELISA confirmed by the IgG avidity test for recent toxoplasmosis. This study highlights how to manage and evaluate pregnant women who are suspected to be infected with toxoplasmosis by using diagnostic tests, especially in a single serum sample indication.