Design and optimization of IgG avidity test for differentiating acute from chronic human toxoplasmosis: A systematic review and meta-analysis

Toxoplasmosis which is caused by T. gondii, is common among humans and animals. T. gondii is a threat to the fetus and individuals with immune disorders, especially patients with acquired immunodeficiency syndrome (AIDS) and individuals who undergo organ transplants. Therefore, quick diagnosis and accurate differentiation of acute and chronic stages are essential. One of the important serological methods in differentiating stages of the disease and the time of acquiring the infection is evaluating the IgG avidity. In this systematic review and meta-analysis, keywords were searched in databases including PubMed, Science Direct, ProQuest, Scopus, and Google Scholar. Included studies were collected after checking the inclusion and exclusion criteria, and according to the PRISMA flow chart. Finally, the data were analyzed by StatsDirect statistical software and random-effects model. A total of 10 studies (26 datasets) were eligible for analysis. The random effects model estimated the prevalence of low IgG avidity in acute toxoplasmosis using in-house IgG avidity tests of 84% and chronic toxoplasmosis infection using in-house IgG avidity of 91%. The IgG avidity test can be a helpful diagnostic tool in differentiating between acute and chronic stages. Also, this review emphasizes that the use of recombinant or chimeric proteins is preferable to TLA in differentiating acute and chronic stages. It can be concluded that choosing more effective antigens (multi-epitope and multi-stage) and performing more detailed studies on the design of an avidity kit to differentiate the stage of infection is required.