Serodiagnosis of toxoplasmosis. The impact of measurement of IgG avidity.

The development of IgG avidity assays has revolutionised serological diagnosis of Toxoplasma infections. The measurement of IgG avidity has shown its power in various clinical settings, especially in situations where timing and differentiation of primary and secondary infections is crucial. However, no laboratory test performed alone is self-sustained, whereby the diagnostic strategy of choice is sequential (or combinatorial) use of high-quality IgG, IgM, IgA and IgG-avidity assays. The impact of IgG avidity measurement will be discussed in five clinical scenarios: acute acquired infection, primary infection during pregnancy, congenital toxoplasmosis, ocular toxoplasmosis and Toxoplasma infection in immunocompromised patients. All in all in toxoplasmosis, superior diagnostic performance is achieved by appropriate combinations of serological, culture-based and PCR techniques.