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

Hartnack, Sonja; Torgerson, Paul R.

doi:10.4172/2161-1068.1000120

Cited by 10 publications

(19 citation statements)

References 30 publications

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“…For the skin tests, PCR, necropsy and culture, the estimated sensitivities and specificities are in accordance of test characteristics from other publications [9, 10, 13, 28, 31, 48, 49]. The wide credibility intervals for the sensitivities (19.6 to 45.6) could be explained by the small data pool of true positive animals.…”

Section: Discussionsupporting

confidence: 83%

Evaluating diagnostic tests for bovine tuberculosis in the southern part of Germany: A latent class analysis

et al. 2017

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Germany has been officially free of bovine tuberculosis since 1996. However, in the last years there has been an increase of bovine tuberculosis cases, particularly in the southern part of Germany, in the Allgäu region. As a consequence a one-time tuberculosis surveillance program was revisited with different premortal and postmortal tests. The aim of this paper was to estimate diagnostic sensitivities and specificities of the different tests used within this surveillance program. In the absence of a perfect test with 100% sensitivity and 100% specificity, thus in the absence of a gold standard, a Bayesian latent class approach with two different datasets was performed. The first dataset included 389 animals, tested with single intra-dermal comparative cervical tuberculin (SICCT) test, PCR and pathology; the second dataset contained 175 animals, tested with single intra-dermal cervical tuberculin (SICT) test, Bovigam® assay, pathology and culture. Two-way conditional dependencies were considered within the models. Additionally, inter-laboratory agreement (five officially approved laboratories) of the Bovigam® assay was assessed with Cohen's kappa test (21 blood samples). The results are given in posterior means and 95% credibility intervals. The specificities of the SICT test, SICCT test, PCR and pathology ranged between 75.8% [68.8–82.2%] and 99.0% [96.8–100%]. The Bovigam® assay stood out with a very low specificity (6.9% [3.6–11.1%]), though it had the highest sensitivity (95.7% [91.3–99.2%]). The sensitivities of the SICCT test, PCR, SICT test, pathology and culture varied from 57.8% [48.0–67.6%] to 88.9% [65.5–99.7%]. The prevalences were 19.8% [14.6–26.5%] (three-test dataset) and 7.7% [4.2–12.3%] (four-test dataset). Among all pairwise comparisons the highest agreement was 0.62 [0.15–1]). In conclusion, the specificity of the Bovigam® assay and the inter-laboratory agreement were lower than expected.

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Section: Discussionsupporting

confidence: 83%

Evaluating diagnostic tests for bovine tuberculosis in the southern part of Germany: A latent class analysis

et al. 2017

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“…In herds containing 600 cows, 1 in 10 tests would be expected to identify 2 FPs while the probability of finding 3 or more FPs is less than 0.02. However, when Sp drops slightly to 0.9967 [18], there is a probability of 0.27 (one in 3.7 herd tests) of identifying two FPs and a probability of 0.18 (1 in 5.6 herd tests) of three FPs.…”

Section: Resultsmentioning

confidence: 97%

“…The DEFRA Sp estimate of 0.999 (Pc = 0.001) was used; for n = 2–3, the 0.9967 Sp estimate by Hartnack and Torgerson [18] (Pc = 0.0033) was also applied.…”

Section: Resultsmentioning

confidence: 99%

“…Similarly, the effect of herd size ( H ) on the probabilities of finding n = 1–3 FP animals in the screening test ( Sp = 0.999) was modelled as B( n , H , Pc) in 50-cow steps (50 to 600 cows). The effect of small changes in Sp on the probability of multiple cows ( n = 2–3) testing FP was explored using an alternative UK BTB data-derived Sp estimate of 0.9967 [18].…”

Section: Methodsmentioning

confidence: 99%

“…For BTB tests, their values may depend on the proportion of infected animals in a stage of infection detectable by the test, whether tested animals have been in contact with infected cattle [18], infection with mycobacteria other than M. bovis [9], [19] and several non-TB status related factors, such as cross-reactivity between SICCT and γIFN [20], the storage of blood samples and other laboratory-associated influences [12] and co-infection with macro parasites [21]. Therefore, when a BTB tester turns up at a farm gate, the exact sensitivity and specificity of the test to be carried out that day are unknown.…”

Section: Introductionmentioning

confidence: 99%

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Towards Risk-Based Test Protocols: Estimating the Contribution of Intensive Testing to the UK Bovine Tuberculosis Problem

Dijk

2013

PLoS ONE

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Eradicating disease from livestock populations involves the balancing act of removing sufficient numbers of diseased animals without removing too many healthy individuals in the process. As ever more tests for bovine tuberculosis (BTB) are carried out on the UK cattle herd, and each positive herd test triggers more testing, the question arises whether ‘false positive’ results contribute significantly to the measured BTB prevalence. Here, this question is explored using simple probabilistic models of test behaviour. When the screening test is applied to the average UK herd, the estimated proportion of test-associated false positive new outbreaks is highly sensitive to small fluctuations in screening test specificity. Estimations of this parameter should be updated as a priority. Once outbreaks have been confirmed in screening-test positive herds, the following rounds of intensive testing with more sensitive, albeit less specific, tests are highly likely to remove large numbers of false positive animals from herds. Despite this, it is unlikely that significantly more truly infected animals are removed. BTB test protocols should become based on quantified risk in order to prevent the needless slaughter of large numbers of healthy animals.

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Detectability of bovine TB using the tuberculin skin test does not vary significantly according to pathogen genotype within Northern Ireland

Wright

Allen

Mallon

et al. 2013

Infection, Genetics and Evolution

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Strains of many infectious diseases differ in parameters that influence epidemic spread, for example virulence, transmissibility, detectability and host specificity. Knowledge of inter-strain variation can be exploited to improve management and decrease disease incidence. Bovine tuberculosis (bTB) is increasingly prevalent among farmed cattle in the UK, exerting a heavy economic burden on the farming industry and government. We aimed to determine whether strains of Mycobacterium bovis (the causative agent of bTB) identified and classified using genetic markers (spoligotyping and multi-locus VNTR analysis) varied in response to the tuberculin skin test; this being the primary method of bTB detection used in the UK. Inter-strain variation in detectability of M. bovis could have important implications for disease control. The skin test is based on a differential delayed type hypersensitivity (DTH) response to intradermal injections of purified protein derivative (PPD) from M. bovis (PPD-B) and Mycobacterium avium (PPD-A). We searched for an association between skin test response (PPD-B skin rise minus PPD-A skin rise) and M. bovis genotype at the disclosing test in culture-confirmed cases using a field dataset consisting of 21,000 isolates belonging to 63 genotypes of M. bovis from cattle in Northern Ireland. We found no substantial variation among genotypes (estimated responses clustered tightly around the mean) controlling for animal sex, breed and test effects. We also estimated the ratio of skin test detected to undetected cases (i.e. cases only detected at abattoir). The skin test detection ratio varied among abattoirs with some detecting a greater proportion of cases than others but this variation was unrelated to the community composition of genotypes within each abattoir catchment. These two lines of evidence indicate that M. bovis genotypes in Northern Ireland have similar detectability using the skin test.

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

Cited by 10 publications

References 30 publications

Evaluating diagnostic tests for bovine tuberculosis in the southern part of Germany: A latent class analysis

Evaluating diagnostic tests for bovine tuberculosis in the southern part of Germany: A latent class analysis

Towards Risk-Based Test Protocols: Estimating the Contribution of Intensive Testing to the UK Bovine Tuberculosis Problem

Detectability of bovine TB using the tuberculin skin test does not vary significantly according to pathogen genotype within Northern Ireland

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