Estimation of receiver-operating characteristic curves to determine accuracy of a competitive enzyme-linked immunosorbent assay for the serodiagnosis of Brucella infection in domestic water buffalo (Bubalus bubalis) and cattle

• Published in: American journal of veterinary research Vol. 64; no. 1; pp. 57 - 64
• Main Authors: Fosgate, Geoffrey T, Adesiyun, Abiodun A, Hird, David W, Johnson, Wesley O, Hietala, Sharon K, Schurig, Gerhardt G, Ryan, Joseph
• Format: Journal Article
• Language: English
• Published: United States 2003
• Subjects: Animals; antibodies; Antibodies, Bacterial - blood; Brucella; Brucella abortus - isolation & purification; brucellosis; Brucellosis, Bovine - blood; Brucellosis, Bovine - microbiology; buffaloes; Buffaloes - microbiology; Cattle; diagnostic techniques; enzyme-linked immunosorbent assay; Enzyme-Linked Immunosorbent Assay - methods; Enzyme-Linked Immunosorbent Assay - veterinary; herds; interspecific variation; Markov Chains; Models, Statistical; Monte Carlo Method; ROC Curve; Sensitivity and Specificity; serodiagnosis; simulation models; Trinidad and Tobago; Trinidad and Tobago
• ISSN: 0002-9645; 1943-5681
• DOI: 10.2460/ajvr.2003.64.57

Objective-To estimate receiver-operating characteristic (ROC) curves for a competitive ELISA (c-ELISA) that is used in serodiagnosis of brucellosis in water buffalo and cattle, to determine the most appropriate positive cutoff value for the c-ELISA in confirmation of infection, and to evaluate species differences in c-ELISA function. Sample population-Sera from 4 herds of cattle (n = 391) and 4 herds of water buffalo (381). Procedure-Serum samples were evaluated for Brucella-specific antibodies by use of a c-ELISA. On the basis of previous serologic test results, iterative simulation modeling was used to classify animals as positive or negative for Brucella infection without the use of a gold standard. Accuracy of c-ELISA for diagnosis of infection was compared between cattle and water buffalo by comparison of areas under ROC curves. Results-A positive cutoff value of 30% inhibition for c-ELISA yielded sensitivity and specificity estimates, respectively, of 83.9 and 92.6% for cattle and 91.4 and 95.4% for water buffalo. A positive cutoff value of 35% inhibition yielded sensitivity and specificity estimates, respectively, of 83.9 and 96.2% for cattle and 88.0 and 97.4% for water buffalo. Areas under ROC curves were 0.94 and 0.98 for cattle and water buffalo, respectively. Conclusion and Clinical Relevance-ROC curves can be estimated by use of iterative simulation methods to determine optimal cutoff values for diagnostic tests with quantitative outcomes. A cutoff value of 35% inhibition for the c-ELISA was found to be most appropriate for confirmation of Brucella infection in cattle and water buffalo.