Comparison of enzyme-linked immunosorbent assay and Fassisi(®) bovine immunoglobulin G (IgG) immunoassay for quantification of bovine IgG in neonatal calf serum

BACKGROUND AND AIM: Rapid tests are routinely used to estimate serum immunoglobulin G (IgG) concentrations in diagnosing a failure of passive transfer (FPT) in calves. The study aimed to compare the Fassisi(®) Bovine IgG (FB-IgG) immunoassay and an enzyme-linked immunosorbent assay for quantifying bovine IgG in neonatal calf serum. MATERIALS AND METHODS: A total of 277 calves of 1-10 days of age were used in this study. Blood samples were obtained, and serum was extracted by centrifuging the samples at 2740× g for 5 min at 20°C. The serum was analyzed using the FB-IgG according to the manufacturer’s specifications. Serum IgG concentrations were also determined by enzyme-linked immunosorbent assay (ELISA-IgG). FPT was defined as a serum IgG concentration <10 mg/mL. RESULTS: The mean ELISA-IgG serum concentration was 8.40 mg/mL (SD=7.02, range=0.10-47.50 mg/mL). FPT prevalence based on the ELISA measurements was 66.8%. The prevalence of partial and full FPT based on the FB-IgG was 54.5%. The ELISA-IgG and FB-IgG results were subjected to correlation and regression analysis. Overall sensitivity and specificity of the FB-IgG were 61.1% and 58.7%, respectively. A statistically significant dependence on age was identified in the results. CONCLUSION: Our findings suggest that the FB-IgG rapid method is less accurate and provides no other advantages over established methods.