An examination of the accuracy of a sequential PCR and sequencing test used to detect the incursion of an invasive species: the case of the red fox in Tasmania

1. Polymerase Chain Reaction (PCR) diagnostic tests are increasingly applied to the identification of wildlife. Yet rigorous verification is rare and the estimation of test accuracy (the probability that true positive and true negative samples are correctly identified – test sensitivity and specificity, respectively), particularly in combination with sequencing, is uncommon. This is important because PCR-based tests are prone to contamination in sampling and the laboratory. 2. Here, we use an experimental case–control approach to estimate the sensitivity and specificity of a sequential PCR-based wildlife detection test used to identify incursions of red foxes into Tasmania from predator faeces (scats). 3. Our results show that the sensitivity of the fox test is high (~94%) for the PCR-based test on its own, but this decreases to ~84% when combined with the DNA sequencing step. In contrast, the specificity increases from ~96% in the PCR only test to ~99.6% after inclusion of the DNA sequ...