Les difficultés d'interprétation de la sérologie de la toxoplasmose

Congenital toxoplasmosis is an infection frequently observed in France. A serological surveillance of pregnant women is practiced. It is helpful to realize a serology of toxoplasmosis before pregnancy to determine the immune status of a subject for this disease. The immunity is acquired for life. For this reason, a serology must not be prescribed when immunity is acquired before pregnancy. If a pregnant woman is not immunized, a monthly serology must be done to detect a primary infection. Diagnosis of primary infection is based on the detection of toxoplasma specific IgM and IgG. The interpretation of the serology is sometimes problematic, particularly when IgM are detected. The results of serology must be interpreted with caution If IgM are always detected in recent infection, they can be also detected in other situations. The knowledge of antibody kinetic during infection and the practise of complementary tests particularly measurement of IgG avidity may help in the interpretation of the results and the dating of toxoplasmosis.