Canine olfactory detection of SARS-CoV-2-infected humans—a systematic review

To complement conventional testing methods for severe acute respiratory syndrome coronavirus type 2 infections, dogs’ olfactory capability for true real-time detection has been investigated worldwide. Diseases produce specific scents in affected individuals via volatile organic compounds. This systematic review evaluates the current evidence for canine olfaction as a reliable coronavirus disease 2019 screening tool. Methods: Two independent study quality assessment tools were used: the QUADAS-2 tool for the evaluation of laboratory tests’ diagnostic accuracy, designed for systematic reviews, and a general evaluation tool for canine detection studies, adapted to medical detection. Various study design, sample, dog, and olfactory training features were considered as potential confounding factors. Results: Twenty-seven studies from 15 countries were evaluated. Respectively, four and six studies had a low risk of bias and high quality: the four QUADAS-2 nonbiased studies resulted in ranges of 81%–97% sensitivity and 91%–100% specificity. The six high-quality studies, according to the general evaluation system, revealed ranges of 82%–97% sensitivity and 83%–100% specificity. The other studies contained high bias risks and applicability and/or quality concerns. Conclusions: Standardization and certification procedures as used for canine explosives detection are needed for medical detection dogs for the optimal and structured usage of their undoubtful potential.