Acurracy assessment of four diagnostic tests for the detection of Giardia and Cryptosporidium in the absence of gold standard: a Bayesian approach
Date
2014
Authors
Palomares Velosa, Jairo Enrique, author
Salman, Mo D., advisor
Ballweber, Lora, committee member
Lappin, Michael, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Giardia and Cryptosporidium are important parasites that cause gastrointestinal disease in numerous animal species including dogs and cats. The accurate diagnostic of this diseases is cucial for the aplication of preventive measures and precise treatment. Estimation of test accuraccy is not difficult when a reference test (gold standard) is available. However, when a gold standard test is not available the Bayesian Latent Class (BLC) Analysis is an effective analytical tool for the estimation of diagnostic accuracy. The aim of this study was to estimate the sensitivity (Se) and specificity (Sp) of four commercial diagnostic kits using BLC. The four diagnostic tests were (1) Merifluor®Direct Fluorecence Antigen (DFA; Giardia/Cryptosporidium; Meridian Diagnostics, Inc., Cincinnati, Ohio), (2) IVD®DFA (Giardia/Cryptosporidium; IDV Research Inc., Carlsbad, CA), (3) IVD Microwell ELISA® (Giardia ; IDV Research Inc., Carlsbad, CA), (4) and IDEXX SNAP® (Giardia ; IDEXX Laboratories Inc., Westbrook, ME). The results from 201 laboratory analysed samples, the prior distributions elicited from three experts, and the consistency of samples as splitting covariate were used as inputs for the BCL models. The estimated Se and Sp of the tests were 87.7% and 97.3% (Merifluor-Cryptosporidium), 68.0% and 99.1% (IVD-Cryptosporidium), 93.6% and 97.9% (Merifluor-Giardia), 96.1% and 97.9% (IVD-Giardia), 86.0% and 98.2% (ELISA-Giardia), and 84.8% and 98.0% (SNAP-Giardia) respectively. The prevalence for non-diarrheic versus diarrheic samples were 2.3% and 4.8% (Cryptosporidium), and 6.9% and 13.5% (Giardia) respectively. We were able to use BLC to assess the sensitivity and specificity of the four commercial diagnostic tests. We ran 36 models and used objective indicators of the performances of the models to choose the best model for estimation of parameters. The results of the study indicated that Merifluor, IVD, and ELISA are equally suitable as diagnostic tests for detection of Giardia. For detection of Cryptosporidium, Merifluor was more accurate than the IVD test.
Description
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Subject
Bayesian
Cryptosporidium
diagnostic test
Giardia
sensitivity
specificity