Evidence-based diagnosis of toxoplasma infection

The aim of this study was to compare the performance of one in-house and fo ur commercially available toxoplasma assays with the Sabin-Feldman dye test . One hundred fifty-seven routine sera and 20 potentially cross-reactive se ra were tested blindly using four commercial assays: Abbott AxSym IgG (Abbo tt Laboratories, UK), Captia Select Toxo-G (Trinity Biotech, UK), Toxreagen t 'Eiken' (Eiken Chemical, Japan) and Toxolatex Fumouze (Fumouze Laboratoir es, France); an inhouse IgG and IgM enzyme immunoassay (EIA); and the gold standard Sabin-Feldman dye test. The sensitivity, specificity and the value s using the formulae for numbers needed to diagnose (NND) and the cost per positive diagnosis (CPPD) were calculated for each assay. These formulae us e the sensitivity and specificity of the assay to allow fur evidence-based comparisons between assays. The NND values for the in-house IgG EIA, AxSym, Eiken and Fumouze latex kits were similar (1.21-1.24), whereas the Captia yielded the poorest value (1.33). The in-house EIA IgG had the lowest CPPD value (pound0.57/$0.91), and the Fumouze and Eiken latex kits had the lowes t CPPD values for commercial assays (pound1.42/$2.27 and pound1.81/$2.90, r espectively). Both assays were simple and straightforward to use. Specialis t laboratories should opt to use in-house assays, as they were most cost-ef fective. Although nonspecialist laboratories could use commercial assays, s pecimens from immunocompromised patients and patients with ocular disease s hould be forwarded to specialist laboratories without prior testing.