Evaluation of a rapid screening immunoassay for antibodies to Toxoplasma gondii

A total of 349 human serum samples were examined for anti-Toxoplasma antibodies by the Murex Single Use Diagnostic System (SUDS) qualitative screening test, indirect hemagglutination assay (IHA), and indirect immunofluorescence assay (IFA). Concordant results with SUDS and IHA were obtained for 91.9% of serum samples; 8.9% were SUDS+ and IHA-; none were SUDS- and IHA+. Comparison of the SUDS assay with IFA showed a concordance of 95.3%, with a sensitivity of 97.5% and a specificity of 94.7%. Moreover, the positive and negative predictive values were 84.9 and 99.2%, respectively, when results of the SUDS assay and IFA were compared. The SUDS assay is a rapid, simple test requiring no instrumentation and can be performed on 50 microliters of serum, features which make this an excellent screening test for detecting anti-Toxoplasma antibodies, particularly in outpatient settings.