Rapid Immunochromatographic Test (RDT) Versus ELISA Technique for Diagnosing Toxoplasmosis among Individuals with Mental Disabilities

Abstract

Background: Toxoplasmagondii is a ubiquitous protozoan parasite that is estimated to infect one-third of the world's human population. In the quest for a suitable diagnostic tool for detection of T. gondii antibodies, the rapid immunochromatographic test has been validated versus the enzyme linked immunosorbent assay (ELISA) technique for diagnosing toxoplasmosis among individuals with mental disabilities. Method: A cross-sectional study was carried out in Alexandria governorate, Egypt during the period from December 2015 to May 2016. Blood samples were collected from 188 mental disabled individuals. The first aliquot was tested by the rapid diagnostic test (RDT), the 2nd and 3rd aliquots were tested quantitatively for anti –T. gondiiIgG and IgM antibodies using ELISA test. Results: The seroprevalence of toxoplasmosis based on RDT was 26.6%, it significantly increased to 48.9% by using ELISA. The diagnostic parameters of RDT versus ELISA for IgG were: sensitivity 54.4%, specificity 100%, PPV 100%, NPV 69.6% with a diagnostic efficiency of 77.7%, while for IGM were: sensitivity 29.03%, specificity 100%, PPV 100%, NPV 87.7% and diagnostic efficiency 88.3%. Cohen's kappa coefficient was 0.549 and 0.406 for IgG and IgM respectively indicating good to moderate agreement between the two tests for detecting IgG and poor to fair agreement for IgM. Conclusion: Although RDT is inferior compared to ELISA, its speed, simplicity, low cost, high specificity and its good diagnostic efficiency in detecting IGG make it an important preliminary screening tool for diagnosing toxoplasmosis in remote endemic areas where facilities for ELISA are not available.