Neospora caninum IgG avidity tests: an interlaboratory comparison

Area of Science:

• Veterinary immunology
• Parasitology
• Food animal health

Background:

• Neospora caninum is an intracellular parasite causing significant economic losses in cattle farming.
• Avidity tests are crucial for differentiating acute from chronic Neospora caninum infections in cattle.
• Accurate diagnostic tools are essential for effective disease management and control strategies.

Purpose of the Study:

• To evaluate and compare the performance of Neospora caninum IgG avidity ELISA tests used by four European laboratories.
• To assess the concordance and agreement between different laboratory protocols for N. caninum IgG avidity testing.
• To identify potential areas for improvement in the standardization and application of avidity assays in bovine neosporosis diagnosis.

Main Methods:

• A panel of 200 bovine sera from documented N. caninum infected animals was analyzed.
• Four European laboratories performed IgG avidity ELISA tests using their established protocols.
• Numeric results were compared using concordance correlation coefficients, and categorized data were analyzed using Kappa statistics.

Main Results:

• Concordance correlation coefficients for numeric results ranged from 0.479 to 0.776.
• Moderate to substantial agreement was observed between laboratories when categorizing results (low, high, intermediate).
• Dichotomized (low/high) results showed better agreement than those including an intermediate category.

Conclusions:

• The first ring test for N. caninum IgG avidity assays revealed moderate agreement among participating laboratories.
• Avidity tests may be less robust than conventional ELISAs, necessitating careful standardization.
• Continuous evaluation of assay performance is essential for reliable diagnosis of bovine neosporosis.