Validation of a Competitive Enzyme-Linked Immunosorbent Assay for Detection of Babesia bigemina Antibodies in Cattle

• Published in: Clinical and Vaccine Immunology 2008-09, Vol.15 (9), p.1316-1321
• Main Authors: Goff, Will L, Johnson, Wendell C, Molloy, John B, Jorgensen, Wayne K, Waldron, Susan J, Figueroa, Julio V, Matthee, Olivier, Adams, D. Scott, McGuire, Travis C, Pino, Ignacio, Mosqueda, Juan, Palmer, Guy H, Suarez, Carlos E, Knowles, Donald P, McElwain, Terry F
• Format: Article
• Language: English
• Subjects: Animals; antibodies; Antibodies, Protozoan - blood; antibody detection; Babesia - immunology; Babesia bigemina; Babesiosis - diagnosis; Babesiosis - veterinary; blood serum; Cattle; Cattle Diseases - diagnosis; Cattle Diseases - parasitology; competitive enzyme-linked immunosorbent assay; enzyme-linked immunosorbent assay; Enzyme-Linked Immunosorbent Assay - methods; Predictive Value of Tests; Protozoan Proteins - immunology; rhoptry-associated protein 1a; ROC Curve; Sensitivity and Specificity; seroprevalence; Time Factors; Veterinary Immunology
• ISSN: 1556-679X; 1556-6811; 1556-679X
• DOI: 10.1128/CVI.00150-08

A competitive enzyme-linked immunosorbent assay (cELISA) based on a broadly conserved, species-specific, B-cell epitope within the C terminus of Babesia bigemina rhoptry-associated protein 1a was validated for international use. Receiver operating characteristic analysis revealed 16% inhibition as the threshold for a negative result, with an associated specificity of 98.3% and sensitivity of 94.7%. Increasing the threshold to 21% increased the specificity to 100% but modestly decreased the sensitivity to 87.2%. By using 21% inhibition, the positive predictive values ranged from 90.7% (10% prevalence) to 100% (95% prevalence) and the negative predictive values ranged from 97.0% (10% prevalence) to 48.2% (95% prevalence). The assay was able to detect serum antibody as early as 7 days after intravenous inoculation. The cELISA was distributed to five different laboratories along with a reference set of 100 defined bovine serum samples, including known positive, known negative, and field samples. The pairwise concordance among the five laboratories ranged from 100% to 97%, and all kappa values were above 0.8, indicating a high degree of reliability. Overall, the cELISA appears to have the attributes necessary for international application.