POC Blood Test Can Help Prevent Toxoplasmosis

Toxoplasma gondii gains access to human hosts when they eat undercooked contaminated meat or are exposed to material contaminated by feces from an acutely infected cat, which usually goes unrecognized.

Vertical transmission from mother to fetus occurs from primary acute infection during gestation. Congenital infection may result in chorioretinitis, hydrocephalus, epilepsy, and death. Serologic screening during gestation allows early antenatal detection and rapid treatment initiation, with economic and patient outcome benefits.

An international team of scientists led by those at the Pritzker School of Medicine (University of Chicago, Chicago, IL, USA) collected and tested 244 samples from 205 individuals in the USA, France and Morocco. Each person of unknown serologic status underwent venipuncture, and status was confirmed either with ARCHITECT Toxo-IgG and IgM system in the Lyon, France Reference Laboratory (n = 95 persons), or for 39 Moroccan patients with Platelia Toxo IgG and IgM system.

The participants provided whole blood via fingerstick. Participants’ fingers were compressed, suffusing the tip, and cleaned with an alcohol wipe. A standard lancet was used for fingerstick. Capillary tubes allowed collection of 30 μL of blood, which was directly applied to the point-of-care (POC) Toxoplasma ICT IgG–IgM–BK test, followed by application of four drops of buffer, provided in the kit. Tests were interpreted at 20 to 30 minutes by individuals performing tests and photographed for later interpretation by two individuals unaware of the subjects’ identity and serologic status.

The scientists reported that a total of 205 persons (244 samples) had their serologic status for T. gondii assessed using the whole blood-variant test and was confirmed using their National Collaborative Chicago-Based Congenital Toxoplasmosis Study (NCCCTS) records (n = 71), or concurrent standard laboratory testing (n = 134). Overall, 101 samples proved seropositive, including five from acutely infected individuals who had IgM/IgG antibodies against T. gondii, while 143 were seronegative. The whole-blood test proved highly sensitive and specific, with a sensitivity of 100% and specificity of 100%. Whole blood, serum-variant, and reference testing demonstrated 100% concordance. Of note, individuals with lower levels of anti-Toxoplasma antibodies infected at remote times and with lower titers were positive in the POC test in the range detected by gold-standard test.

The test is also inexpensive as it costs USD 4.0 to USD 5.0 per test. Pregnant women at risk should be tested eight to 10 times, once a month during pregnancy, beginning in the 12th week, then once more four to six weeks after delivery. Total cost for repeated tests is about USD 40.00 to USD 50.00. Hospitals and clinics in developed countries charge substantially more.

Rima McLeod, MD, a professor of ophthalmology and lead author of the study, said, “The test is sensitive and specific, quick and easy to perform, equipment-free, and easily utilized. Results are available in half an hour while the patient is seeing the doctor. A positive result can be confirmed quickly, so health care providers can immediately begin treatment.” The study was published on August 16, 2018, in the journal PLOS Neglected Tropical Diseases.

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Pritzker School of Medicine