How to detect current toxoplasma infection

Abstract

This study seeks to identify the best way to detect current toxoplasma infection for district general hospital laboratories. One hundred ‘ordinary’ and 174 ‘difficult’ sera are categorised into either an ‘evidence’ or ‘no evidence’ group for current toxoplasma infection. Twelve test protocols are investigated using different combinations of one whole antibody latex test (Eiken Toxoreagent), one in-house specific IgG enzyme-linked immunosorbent assay (ELISA) and three specific IgM assays (Toxo-ISAGA, in-house BAM ELISA IgM and Toxonostika ELISA M). The Eiken latex and in-house IgG assays produced significantly fewer false-negative results than were obtained with the single IgM test or the IgG and IgM test protocols (P<0.05), but a greater number of false-positive results (102/274 and 115/274, respectively). Of the IgM assay test protocols, the three IgM assays in combination produced the least number of false-negative results (1/274). However, a significantly greater number of false-positive results were produced than with one or two IgM tests or an IgG and any IgM test in combination (P<0.001). We recommend testing with three IgM tests, or a whole antibody (Eiken) or IgG-specific assay, and that positive or clinically important negative samples be referred to a reference laboratory for confirmation.