BIOLOGICAL DIAGNOSIS OF TOXOPLASMOSIS DUR ING PREGNANCY - METHODS, INTERPRETATIONS AND PRACTICAL RECOMMENDATIONS

The biological diagnosis of infection with Toxoplasma gondii during pr egnancy can be performed: either (1.) with direct methods (microscopic examination, in vitro isolation on cell cultures, histology, detectio n of T. gondii DNA) or (2.) by indirect serological methods in order t o demonstrate specific antibodies in serum. An appropriate combination of complementary techniques (antibody detection in serum and demonstr ation of the parasite) must lead, in the majority of cases, to a preci se diagnosis of congenital toxoplasmosis. Serological examination of a woman before or at the beginning of pregnancy serves to distinguish b etween women with or without specific immune status. The diagnosis of a seroconversion during pregnancy causes few difficulties particularly if carefully followed up. However, it is rather difficult to date an infection during pregnancy based only on a initial positive sample wit h the presence of anti-T. gondii IgM. Thus, around 1 to 5% of serologi cal examinations during pregnancy cause practical problems of interpre tation. A certain number of recommendations are suggested to the labor atory supervisor: 1. Pregnant women should be systematically tested fo r specific anti-T. gondii IgG or total Ig and IgM. The choice of the t echniques serves to reliably distinguish women without anti-T. gondii antibodies (women at risk for primary infection) from those with anti- T. gondii antibodies (immune women). 2. Interpretations of results sho uld be well formulated to be understandably to the practitioner who mu st adequately inform the patient and determine the proper medical acti on on the basis of the serological results. 3. Sera should be preserve d systematically for a minimum of 12 months (whatever the results may be). 4. Cases or situations causing problems should be referred to a s pecialized laboratory for expert advice.