Evaluation of recombinant Toxoplasma gondii matrix antigen MAG1 for toxoplasmosis screening in HIV/AIDS patients

Timely serodiagnosis of Toxoplasma gondii is critical for HIV/AIDS patients, in whom latent infection can reactivate into life-threatening toxoplasmic encephalitis. This study aimed to evaluate the diagnostic performance of a novel recombinant T. gondii matrix antigen 1 (TgMAG1)-based indirect ELISA and a commercial latex agglutination test (LAT) for detecting anti-T. gondii IgG in HIV/AIDS patients, using the Sabin-Feldman dye test (DT) as the reference standard. A secondary objective was to determine the current prevalence of latent toxoplasmosis in this population in Thailand. We conducted a comparative serological evaluation using 348 residual clinical specimens collected from 2016 to 2019 from HIV/AIDS patients. All samples were tested using the in-house TgMAG1 ELISA, a commercial LAT, and the DT. The sensitivity, specificity, and agreement (kappa statistic) of each index test were calculated against the DT. The DT identified a T. gondii seroprevalence of 12.36% (43/348; 95% CI: 8.94-16.64). Compared to the DT, the TgMAG1-ELISA demonstrated a sensitivity of 72.09% and a specificity of 93.11%, with moderate agreement (κ = 0.598). The LAT showed a similar sensitivity of 69.76% but a higher specificity of 97.04%, achieving substantial agreement with the DT (κ = 0.696). In conclusion, both the TgMAG1-based ELISA and LAT demonstrated high specificity but moderate sensitivity compared to the reference standard. Consequently, while these assays are valuable screening tools in settings lacking the DT, their results require careful interpretation and potential confirmation in high-risk populations.