Bayesian Assessment of the Accuracy of a PCR-Based Rapid Diagnostic Test for Bovine Tuberculosis in Swine

Abstract

Infection with the Mycobacterium bovis (M. bovis) causes a disease referred to as bovine tuberculosis (bTB), which affects a wide range of mammal hosts. Many countries have implemented control and eradication plans that have resulted in variable levels of efficacy and success. Although bTB is a notifiable disease in Argentina, and a control plan that targets cattle herds has been in place for decades, M. bovis is still prevalent in cattle, swine, and certain wild species. The aim of the paper here was to assess the sensitivity (Se), specificity (Sp), and positive and negative predictive values (PPV and NPV) of PCR from tissue, which is a test for rapid M. bovis detection in swine. Bacteriological culture was also performed for comparison purposes. A Bayesian approach was applied to estimate the accuracy of the diagnostic tests, PCR and bacteriological culture, in 266 swine samples with bTB-like lesions recovered during routine official inspections at slaughterhouses. A one-population model, assuming conditional dependence between test results, and incorporating prior information on the performance of the tests obtained from the literature, was used to estimate the tests Se and Sp. The accuracy of the combined (in parallel) application of both tests was also estimated. The Se of the PCR (82.9%) was higher than the Se of the bacteriological culture (79.9%), whereas the Sp of both tests was similar (88.5 and 89.0%, respectively). Furthermore, when both techniques were assessed in parallel, the Se of the diagnostic system increased substantially (Se = 96.6%) with a moderate Sp loss (Sp = 78.8%; PPV = 92.8%; NPV = 89%). Results suggest that the PCR, or the combined application of bacteriological culture and PCR, may serve as an accurate diagnostic tool to confirm bTB in swine samples. Results here will help the design and implementation of effective surveillance strategies for the disease in swine of Argentina and other settings in which the disease is prevalent.

Real-Time PCR Validation for Mycobacterium tuberculosis Complex Detection Targeting IS6110 Directly From Bovine Lymph Nodes

“…IS 6110 is a target sequence with multiple copies only present in pathogens belonging to MTC, commonly used for MTC detection by PCR ( 7 , 12 , 17 , 18 ). Besides IS 6110 , other targets have also been used for the same purpose, including IS 1081 ( 16 , 19 ), hupB ( 20 , 21 ), 16S-23S rRNA internally transcribed spacer ( 22 ), p34 gene ( 23 ), TbD1 ( 24 ), or mpb70 ( 11 ) with varying results.…”

“…It is reported that culture is an imperfect, laborious, and time-consuming technique that requires high biosecurity facilities and relatively high expertise (7,8), whose performance can, moreover, be affected by several factors (8)(9)(10)(11). A major drawback is the delayed culturing process (up to 2-3 months), making the time required to reach a final diagnosis longer (7,11,12).…”

Bovine tuberculosis in safari park in Brazil

“…The use of techniques and methods involving molecular biology, such as Polymerase Chain Reaction (PCR), has reduced the time required for the diagnosis of bTB. Several studies demonstrate the use of PCR in complementing the identification of M. bovis (Zumárraga et al 2012, Barandiaran et al 2019, Fico et al 2019, such as the work of Elsayed & Amer (2019), who used PCR directly from tissue samples, demonstrating the technique's speed compared to cultivation for species identification. Sales et al (2014) compared different primers for the detection of M. bovis, proving that Mb.400 primers, targeting fragments flanking the region of differentiation 4 (RD4), are the ones that demonstrated the best results in the PCR for bTB.…”

Intra-vitam Diagnosis of Tuberculosis in Pigs: Concordance Between Interferon-Gamma Release Assay and Comparative Tuberculin Skin Test

“…However, it has been shown how bacteriology has its limitations (27) and that sensitivity can be improved by the parallel use of PCR on organs and culture for the diagnosis of bTB in swine (28). This could explain the positivity of intra-vitam tests in culture-negative animals with or without VLs.…”