Comparative Diagnostic Performance of Total IgG , IgG1 and IgG4 ELISA Responses to a Chimeric Rec

ABSTRACT

Accurate diagnosis of strongyloidiasis remains challenging, and serological assays are widely used in clinical practice. This study evaluated a recombinant SsIR/Ss1a fusion antigen for detecting total IgG, IgG1, and IgG4 antibodies. Serum samples were obtained from 30 parasitologically confirmed Strongyloides stercoralis cases, 30 healthy controls, and 36 individuals with other helminth infections. Indirect ELISA was performed using the recombinant fusion antigen. Diagnostic performance was assessed by ROC curve analysis, with optimal cut‐off values determined using Youden's index. Sensitivity, specificity, and positive and negative predictive values (PPV, NPV) were calculated. Total IgG showed the highest diagnostic accuracy (AUC = 0.943), with 93.3% sensitivity, 95.5% specificity, 90.3% PPV, and 96.9% NPV. IgG4 showed lower sensitivity (80.0%) but higher specificity (97.0%), whereas IgG1 showed lower sensitivity (73.3%) and specificity (92.4%). Cross‐reactivity was limited and occurred primarily in toxocariasis samples. IgG subclass analysis revealed distinct performance characteristics, with IgG4 offering higher specificity at the expense of sensitivity. These results indicate that antibody isotype selection materially affects the diagnostic behaviour of recombinant antigen‐based ELISA. These findings suggest that total IgG is suitable for screening purposes, whereas IgG4 may be advantageous in settings requiring greater specificity.