An inexpensive, accurate test that detects infections with the parasite Toxoplasma gondii can provide results within 30 minutes from a finger-prick in a doctor’s office or within an hour from a small blood sample tested in a local medical laboratory.
The new test can also identify false positives in other types of commercial diagnostic tests for toxoplasmosis, providing swift reassurance to uninfected pregnant women and their doctors and facilitating timely interventions to protect a foetus against toxoplasmosis in acutely infected pregnant mothers. These findings appear in a study, led by toxoplasmosis specialist Rima McLeod MD, Professor of Ophthalmology and Visual Science and Pediatrics at the University of Chicago, recently published in the journal PLOS Neglected Tropical Diseases.
"By using this approach and test to monitor pregnant women monthly for Toxoplasma infections, beginning before or very early in pregnancy, we can help prevent infections of their babies," said McLeod. "This test can also contribute to solving the problem of false positives from other Toxoplasma tests, inexpensively, which can help reassure pregnant women and their doctors."
Early detection of T. gondii in previously uninfected pregnant women is key to limiting the damage of toxoplasmosis in unborn babies. Pictured above is a toxo cell - a form of the toxoplasmosis-causing parasite that can be transmitted through the placenta to a foetus.
Developed by LDBIO Diagnostics of Lyon, France, and as found by the authors, the Toxoplasma ICT IgG-IgM point-of-care diagnostic test provides rapid results on immuno-chromatographic paper. The researchers note that starting as early as possible, uninfected women should have their antibody status tested once a month during pregnancy, beginning before the 12th week and then four to six weeks after delivery.
The research analyses 12 new individual studies conducted by scientists in the United States, France and Colombia. Researchers examined the feasibility of using the ICT in multiple clinical circumstances and types of medical care as well as how it was perceived by patients, families and frontline health care workers. They also sought to use the ICT as a back-up diagnostic tool to detect false positive tests in standard commercial tests for IgM antibodies.
The paper includes collation of the new, previously unpublished research with earlier studies from the University of Chicago, Stanford University and the Palo Alto Medical Foundation in the US, France, Morocco and Tunisia, revealing the test to be more than 97.5% (blood), 99% (serum) sensitive and 100% specific on a large scale and in multiple countries and settings. Scientists tested the serum or blood samples of more than 5,500 individuals in conjunction with more than 20,000 separate assays using reference laboratory comparator tests. The ICT out-performed other non-specialty reference laboratory tests across the studies and proved it could be used to correct the errors of other commercially available screening tests.
Although eight US states require the reporting of toxoplasmosis cases to the CDC, doctors in the US do not yet routinely test for T. gondii in pregnant women. In France and Austria, screening for toxoplasmosis during pregnancy has proven to be cost effective; an earlier study calculated similar benefits for the US.
- Zhou Y, Leahy K, Grose A, et al. Novel paradigm enables accurate monthly gestational screening to prevent congenital toxoplasmosis and more. PLoS Negl Trop Dis. 2024;18(5):e0011335. Published 2024 May 28. doi:10.1371/journal.pntd.0011335.