Systematic serologic screening for toxoplasmosis in pregnancy.

Abstract

To determine which serologic method or combination of methods could most effectively identify acute toxoplasmosis during pregnancy and to assess whether systematic screening is practical and cost-effective. Using basic serologic tests (direct agglutination test and immunosorbent agglutination assay), we screened 2104 women for toxoplasmosis. Immunoglobulin M (IgM)-reactive patients (IgM immunosorbent agglutination assay score of at least 3) were studied by differentiating serologic tests performed sequentially. Specific immunity was found in 874 pregnant women (41.6%); 155 (7.4%) were IgM-reactive and 12 (0.6%) had acute toxoplasmosis. Using a reduced immunosorbent agglutination assay score of at least 3 (normally a score of at least 6 is used), acute toxoplasmosis was identified in 11 women at their first prenatal visit, including two in whom acute infection would not have been detected by a score of 6 or more until 9 weeks later. One additional nonimmune patient with acute infection was identified only by follow-up serologic testing. Systematic screening followed by sequential differentiating serologic tests is practical and cost-effective for the diagnosis of acute toxoplasmosis during pregnancy.