Diagnostic Performance of an In-House-Developed IgG Western blot for the Early Detection of Congenital Toxoplasmosis: A Retrospective Study

Objective: To evaluate the diagnostic performance of an in-house-developed IgG Western blot (WB) for congenital toxoplasmosis and its complementary role with other serological markers. Methodology: For this purpose, the study utilized 42 mother–child pairs, evaluating the WB in comparison with a Composite Reference Standard (CRS). Cohen’s Kappa coefficient measured agreement, while McNemar’s test compared WB with Combined Serology (neonatal IgG titers higher than the mother’s (IgG↑), IgM, IgA). Results: The WB demonstrated a sensitivity of 75.0% and a specificity of 100.0%. Kappa indicated substantial agreement with the CRS (κ = 0.67; 95% CI: 0.44–0.89). McNemar’s test found no statistically significant difference between WB and Combined Serology (p = 0.7516). Crucially, WB detected 4 unique cases missed by Combined Serology, and Combined Serology detected 6 cases missed by WB. This complementarity increased the overall diagnostic rate from 82.14% to 96.43%. Conclusions: IgG-WB is a crucial complementary diagnostic tool, especially for asymptomatic newborns. Its integration significantly improves diagnostic certainty, allowing for more timely treatment for congenital toxoplasmosis.