A recent study in PLOS Neglected Tropical Diseases looked at whether a cost-effective finger-prick whole-blood test for toxoplasmosis can reliably detect the presence of the parasite, Toxoplasma gondii(T. gondii). In toxoplasmosis cases, timely intervention is imperative since the fetus is at most risk for contracting the disease in the third trimester. However, conventional serologic testing can be cost-prohibitive and necessary equipment is not always available.
The researchers recruited participants from the National Collaborative Chicago-Based Congenital Toxoplasmosis Study (NCCCTS) as well as obstetrical patients in Chicago and Morocco. Participants provided whole blood via fingerstick. A total of 205 individuals (244 samples) were included in the study and had their serologic status for T. gondiiassessed using the whole blood-variant test and results were confirmed using either their NCCCTS records or through concurrent standard laboratory testing. Overall, 101 samples proved seropositive, including five from acutely infected individuals who had IgM/IgG antibodies against T. gondii, while 143 samples were seronegative. The authors defined seropositive as having detectable anti-Toxoplasma immunoglobulin G (IgG) and/or immunoglobulin M (IgM).
The whole blood test was found highly sensitive and specific with a sensitivity of 100% (95% CI: 96.41%-100%) and specificity of 100% (95% CI: 97.45%-100%). The authors found 100% concordance with whole-blood, serum variant, and reference testing as well.
The authors believe there are several advantages to their point-of-care test. The test is much more convenient and less invasive than conventional serologic testing. It also has the potential to have greater availability given its low cost. It is also much quicker with results available for interpretation within 20-30 minutes. There are some noted disadvantages, however. It requires initial, alternative testing for those who are seropositive to distinguish IgG from IgM and requires follow-up testing for seroconversion when used for screening during gestation. The required fingerstick may cause discomfort for the patient and may also need to be performed multiple times in cases with technical difficulties. There is also some training involved in performing and interpreting the test. However, the authors believe that the high sensitivity and specificity of the test as well as its low cost can help reduce morbidity and mortality from congenital toxoplasmosis.