Current and Emerging Techniques for Diagnosis of Toxoplasmosis in Pregnancy: A Narrative Review

Abstract

Toxoplasma gondii is an intracellular parasite capable of crossing the placenta in pregnancy and infecting the developing fetus, leading to various congenital anomalies and even abortion. Acute Toxoplasma infection is responsible for almost all cases of congenital toxoplasmosis in immunocompetent pregnant women. Prenatal screening for acute toxoplasmosis primarily involves maternal serology and fetal ultrasound imaging. When serological or ultrasound findings suggest acute infection, further diagnostic tests are necessary to confirm fetal infection. Currently, molecular methods to detect the parasite's DNA, including polymerase chain reaction-based methods, on amniotic fluid are the gold standard tests for the diagnosis of congenital toxoplasmosis. In this review, we aim to discuss various aspects of screening and diagnostic methods for toxoplasmosis in pregnancy, including (i) current serological assays, screening approaches, and future perspectives; (ii) the role of imaging techniques, with an emphasis on ultrasound; (iii) principles and recent advances in diagnostic molecular methods; (iv) emerging techniques, such as point-of-care-based tests and biosensors, and microRNAs as novel biomarkers of acute infection; and (v) an overview of screening programs in different countries, important epidemiological determinants, and recommendations for Toxoplasma screening health policies.

Keywords: Congenital toxoplasmosis; Molecular diagnostics; Pregnancy; Serological assays; Toxoplasma gondii.

Fig. 1:

Diagnostic approaches for toxoplasmosis in pregnancy. Serological testing identifies specific antibodies in maternal blood to determine the infection stage. Ultrasound is the primary imaging technique for screening fetal anomalies associated with congenital toxoplasmosis. Amniocentesis can confirm fetal infection when indicated (Original figure)

Fig. 2:

Key features and principles of serological techniques for detecting T. gondii infection Abbreviation: DT: dye test, ISAGA: immunosorbent agglutination assay, IFAT: immunofluorescence antibody test, ELISA: enzyme-linked immunosorbent assay (Original figure)

Fig. 3:

The proposed algorithm for prenatal screening and diagnosis of congenital toxoplasmosis. Abbreviation: US: ultrasound, pt: patient, GA: gestational age, Rx: treatment, CT: congenital toxoplasmosis, TMP-SMX: Trimethoprimsulfamethoxazole, HIV: human immunodeficiency virus, CD4: CD4+ T lymphocyte, F/U: follow-up, DT: dye test, ELISA: enzyme-linked immunoassay, HS/AC: differential agglutination, PCR-AF: polymerase chain reaction on amniotic fluid, W/U: work-up (Original figure)