ObjectiveTo assess the diagnostic performance of serum anti-toxocara immunoglobulin G (anti-T-IgG) in ocular toxocariasis (OT) patients. MethodsA diagnostic tests. A total of 109 patients (109 eyes) with clinically-suspected OT who treated in Department of Ophthalmology of Xuzhou First People’s Hospital from June 2015 to December 2022 were included. Patients were divided into two groups, 76 with OT and 33 with non-OT, according to the clinical manifestations and Goldmann-Witmer coefficient. Paired serum and intraocular fluid samples from each patient were collected and analyzed for specific anti-T-IgG using enzyme linked immunosorbent assay. Mann-Whitney test was performed for comparison between groups. The area under the receiver operating characteristic curve (ROC) was used to assess the diagnostic performance of serum anti-T-IgG. Kappa analysis was performed to examine the consistency of serum or intraocular fluid anti-T-IgG positive rate with OT diagnostic result. Spearman’s rank correlation test was performed to assess the association. ResultsCompared with the non-OT group, the proportions of children and history of exposure to cats and dogs (χ2=9.785, 12.026) were significantly higher in OT group, and the differences were statistically significant (P＜0.01). The positive rate (χ2=24.551) and U value (Z=−4.379) of serum anti-T-IgG in OT group were higher than those in non-OT group, and the differences were statistically significant (P＜0.000 1). The recommended serum anti-T-IgG cut-off value of 11 U had 0.72 sensitivity, 0.79 specificity, 0.89 positive predictive value, 0.55 negative predictive value, and 0.77 area under the ROC with 95% confidence interval (CI) 0.669-0.860. Correlation analysis showed that serum anti-T-IgG was positively correlated with intraocular fluid anti-T-IgG (rs=0.520, 95%CI 0.363-0.648, P＜0.000 1). The Kappa values of serum and intraocular fluid anti-T-IgG positive rate with OT diagnosis were 0.457 (95%CI 0.292-0.622) and 0.711 (95%CI 0.582-0.840), respectively. The Kappa value of serum anti-T-IgG positive rate with OT diagnosis was lower than that of intraocular fluid. ConclusionThe sensitivity and specificity of serum anti-T-IgG and the consistency between serum anti-T-IgG positive rate and OT diagnosis are low, suggesting that serum anti-T-IgG level cannot be used as a basis for OT diagnosis.