The Accuracy of the Single Intradermal Comparative Skin Test for the Diagnosis of Bovine Tuberculosis-Estimated from a Systematic Literature Search

Abstract

Introduction None of the currently available diagnostic tests can be considered as having both 100% sensitivity and 100% specificity, i.e. to be a perfect gold standard being able to determine accurately the infection status for each animal tested. In the UK, the Department for Environment, Food and Rural Affairs (DEFRA) claims a specificity of the single intradermal comparative cervical tuberculin test (SICCT) of 99.9% [12]. In the case of diseases with a low prevalence and a test specificity of less than 100%, the number of false-positive individuals can be higher than the number of infected animals. Several reviews [13-15] and a large number of studies report a wide range of diagnostic performances of the SICCT. However, despite these studies there has been no systematic evaluation of the performance of the SICCT or indeed any of the tests used in the diagnosis of bTB. This is in contrast to the evaluation of diagnostic procedures for tuberculosis in humans [16]. A meta-analysis of field studies on bovine tuberculosis skin tests in United States cattle herds identified seven publications together for the caudal fold tuberculin test and the serial interpretation of the caudal fold and the comparative cervical tuberculin test published between 1953 and 2011 [17]. Typically culture is used as a confirmatory test for a SICCT positive animal. While diagnostic specificity of bacteriological culture maybe assumed to be 100%, diagnostic sensitivity is less than 100%, leading to a potential misclassification of samples, i.e. false-negative test results. Although no perfect gold standard with both sensitivity and specificity of 100% for the diagnosis of bTB exists, it should be possible to obtain unbiased estimates of diagnostic performance, Abstract Background: Bovine Tuberculosis (bTN) elimination programs are based on test-and-slaughter strategies. No diagnostic test used in the control of Bovine Tuberculosis (bTB), a zoonotic disease, is a perfect gold standard having a diagnostic sensitivity and specificity of 100%.