Meriam N Saleh1,2, Jack R Heptinstall3, Eileen M Johnson2, Lora R Ballweber4, David S Lindsay1, Stephen Werre1, Joel F Herbein3, Anne M Zajac1. 1. Department of Biomedical Sciences & Pathobiology, Virginia Tech, Blacksburg, Virginia. 2. Department of Veterinary Pathobiology, Oklahoma State University, Stillwater, Oklahoma. 3. Scientific Affairs, TECHLAB Inc., Blacksburg, Virginia. 4. Department of Microbiology, Immunology & Pathology, Colorado State University, Fort Collins, Colorado.
Abstract
BACKGROUND: An evaluation of currently available in-clinic diagnostic tests for Giardia duodenalis infection of dogs and cats has not been performed. In addition, there is discordance among published diagnostic comparisons. The absence of a true gold standard for detecting Giardia duodenalis also complicates diagnostic evaluations. OBJECTIVES: To evaluate diagnostic tests commercially available in the United States for detecting Giardia duodenalis in dogs and cats, in comparison to a widely used reference test, the direct immunofluorescent assay (IFA), and also to compare the results of 2 methods of analysis: comparison of diagnostic tests to a reference test (IFA) and Bayesian analysis. ANIMALS: Fecal samples from a convenience sample of 388 cats and dogs located in Colorado, Oklahoma, and Virginia. METHODS: Fecal samples were tested for Giardia duodenalis by zinc sulfate centrifugal fecal flotation and 4 different commercial diagnostic immunoassays. Results were analyzed via Bayesian analysis and by comparison to the IFA as the reference test. RESULTS: Sensitivity and specificity by comparison to IFA was ≥82% and ≥90%, respectively, for all diagnostic tests in dogs and cats. When analyzed via Bayesian analysis, sensitivity and specificity were ≥83% and ≥95%, respectively. When ZnSO4 centrifugal fecal flotation results were combined with immunoassay results, there was no longer a significant difference between the sensitivities of the commercial in-clinic immunoassays. CONCLUSION AND CLINICAL RELEVANCE: The Bayesian analysis validates using IFA as the reference test. Differences in commercial in-clinic immunoassay sensitivities can be mitigated when the results are combined with ZnSO4 centrifugal fecal flotation results.
BACKGROUND: An evaluation of currently available in-clinic diagnostic tests for Giardia duodenalis infection of dogs and cats has not been performed. In addition, there is discordance among published diagnostic comparisons. The absence of a true gold standard for detecting Giardia duodenalis also complicates diagnostic evaluations. OBJECTIVES: To evaluate diagnostic tests commercially available in the United States for detecting Giardia duodenalis in dogs and cats, in comparison to a widely used reference test, the direct immunofluorescent assay (IFA), and also to compare the results of 2 methods of analysis: comparison of diagnostic tests to a reference test (IFA) and Bayesian analysis. ANIMALS: Fecal samples from a convenience sample of 388 cats and dogs located in Colorado, Oklahoma, and Virginia. METHODS: Fecal samples were tested for Giardia duodenalis by zinc sulfate centrifugal fecal flotation and 4 different commercial diagnostic immunoassays. Results were analyzed via Bayesian analysis and by comparison to the IFA as the reference test. RESULTS: Sensitivity and specificity by comparison to IFA was ≥82% and ≥90%, respectively, for all diagnostic tests in dogs and cats. When analyzed via Bayesian analysis, sensitivity and specificity were ≥83% and ≥95%, respectively. When ZnSO4 centrifugal fecal flotation results were combined with immunoassay results, there was no longer a significant difference between the sensitivities of the commercial in-clinic immunoassays. CONCLUSION AND CLINICAL RELEVANCE: The Bayesian analysis validates using IFA as the reference test. Differences in commercial in-clinic immunoassay sensitivities can be mitigated when the results are combined with ZnSO4 centrifugal fecal flotation results.
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Authors: Meriam N Saleh; Jack R Heptinstall; Eileen M Johnson; Lora R Ballweber; David S Lindsay; Stephen Werre; Joel F Herbein; Anne M Zajac Journal: J Vet Intern Med Date: 2019-04-13 Impact factor: 3.333
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