Toxoplasmosis Immune Status in Pregnancy Determined by Immunochromatography Assay

Toxoplasmosis is a disease that results from infection with the Toxoplasma gondii parasite, one of the world's most common parasites. Infection usually occurs by eating undercooked contaminated meat, exposure from infected cat feces, or mother-to-child transmission during pregnancy.

Obstetrical toxoplasmosis involves the systematic serological screening for Toxoplasma‐specific IgG and IgM antibodies which is usually performed using enzyme-linked immunosorbent assay (ELISA) techniques. Screening tests used routinely are not sufficient and require additional techniques to determine the Toxoplasma immune status.

Medical Parasitologists at the Pasteur Institute of Tunis (Tunis, Tunisia) selected 39 sera collected during the period 2015 to 2018 in the setting of the routine Toxoplasma serological screening in pregnant women. Sera were selected according to their anti‐Toxoplasma IgM and IgG antibodies titers in “Platelia Toxo IgG, IgM” (Bio-Rad, Marnes-la-Coquette, France).

Western blot Toxo II IgG (LDBIO DIAGNOSTICS, Lyon, France) was performed for all the sera in order to precisely determine their exact Toxoplasma immune status. The LDBIO Toxoplasma ICT IgG‐IgM is a rapid, simple, qualitative test based on immunochromatography technology (ICT, lateral flow). A positive test reveals the presence of anti‐Toxoplasma antibodies, but does not distinguish between IgG and IgM classes.

The scientists reported that in the absence of IgM and presence of IgG equivocal titers in ELISA, Toxoplasma ICT IgG‐IgM and WB Toxo II results were 94.7% concordant. All positive samples in WB were also positive in ICT. The sensitivity in the detection either of low IgG titers in absence of IgM or of specific anti‐Toxoplasma IgM was 100%. Only one serum with equivocal IgG titer by ELISA and negative with Toxo II IgG test revealed positive in ICT. However, this serum showed a P30 band in WB analysis. On the other hand, three sera positive in ELISA IgM and negative in ELISA IgG revealed positive in ICT and negative in WB Toxo II IgG, the reference test.

The authors concluded that their results confirm the high sensitivity of Toxoplasma ICT IgG‐IgM in detecting both specific anti‐Toxoplasma IgG and IgM, and highlight the usefulness of this rapid test as a first or second‐line Toxoplasma serological test in pregnant women. The study was published on March 15, 2021 in the Journal of Clinical Laboratory Analysis.

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Pasteur Institute of Tunis
Bio-Rad
LDBIO DIAGNOSTICS