A simple and economic slide micro-immunoenzymatic (micro-SIA) test for epidemiological studies of toxoplasmosis

A slide micro-immunoenzymatic assay (micro-SIA) to detect antibodies to non-particulate Toxoplasma gondii antigens is described. This assay allows the diagnosis of toxoplasmosis infection in about 1 hr. Twenty-four determinations can be performed per slide. Five hundred ng of antigen and 5 or 10 microliters drop of each reactive are necessary per well. The clear contrast of colours obtained for negative and positive sera after the test is finished, allows direct discrimination of the results. However, it is possible to quantify the results of the reaction using a minireader. Sera dilution cutoff value, determined as the most frequent titre for the general population, is 1:100. The toxoplasma micro-SIA correlates well with indirect immunofluorescence (IIF), its sensitivity is at least three times as much as IIF. The test has an intra and inter assay variation coefficient of 5.46% and of 6.24% respectively. Sera obtained at random from argentinian people were analyzed and a 56% of infection was found. The main features of the Toxoplasma micro-SIA are its simplicity, sensitivity, reproducibility, and the virtual absence of background making it very suitable for screening tests.