Evaluation of a recombinant antigen ELISA for the diagnosis of acute toxoplasmosis and comparison with traditional antigen ELISAs.

An evaluation of five ELISA methods for the diagnosis of acute toxoplasmosis was undertaken by comparing a laboratory-produced ELISA employing two recombinant Toxoplasma gondii polypeptides as antigen with a laboratory-produced ELISA and three commercially available ELISAs employing traditional parasite antigen preparations derived from whole tachyzoites. With a panel of 75 sera from patients who showed either serological and clinical evidence of acute toxoplasmosis, or of diseases caused by other infectious agents, or from patients who showed no evidence of infectious disease, the ELISAs gave overall positive predictive values of 81.6-100%, negative predictive values of 87.8-100%, sensitivities of 81.3-100%, and specificities of 83.7-100%. No two ELISAs gave identical results with all sera tested. In total, the ELISA based on the two recombinant T. gondii polypeptides appeared to be the most specific ELISA in this comparison, showing positive predictive values and specificities of 100% for all groups of patients tested. The overall negative predictive value for this ELISA was 87.8% and the sensitivity was 81.3%. Therefore, the ELISA based on recombinant antigen appears to be a promising advance in the serological diagnosis of acute toxoplasmosis.