Evaluation of commercial serodiagnostic kits for toxoplasmosis

Abstract

To evaluate commercially available diagnostic kits for human immunoglobulin G to Toxoplasma gondii, we purchased three enzyme immunoassay (EIA) (Cordia-T, Toxo Bio-EnzaBead, and Toxoelisa), two indirect hemagglutination (IHA) (TPM-Test and ToxHAtest), one fluoroimmunoassay (Toxoplasma-G FIAX), and one latex agglutination (Eiken Toxotest-MT) kit from U.S. suppliers. A total of 100 serum specimens, including 27 that were negative (less than 1:16) and 73 that were positive for the various titers in the Toxoplasma indirect immunofluorescence (IIF) test, were tested once with each kit; serum samples with discrepant results were retested. Qualitatively, results obtained with the Toxo Bio-EnzaBead EIA, the TMP-Test IHA, and FIAX, and the Toxotest-MT latex agglutination kits agreed exactly with those of IIF. Although all IIF-positive serum samples were detected by the Cordia-T and the Toxoelisa EIAs, four samples determined to be negative by IIF were identified as positive with the Cordia-T kit, and six negative samples by IIF were determined to be positive with the Toxoelisa kit. Results of the ToxoHAtest IHA kit were extremely difficult to read. Quantitatively, the seven kits were difficult to compare because the expression of results was not standardized. Of the four kits that gave positive results in titers, Toxoplasma-G FIAX had the closest agreement with IIF, as determined by the Spearman rank correlation coefficient (0.9168), followed by the Eiken Toxotest-MT (0.8293), the Toxo Bio-EnzaBead (0.7553), and the TPM-Test (0.7206) kits.