Remote Medical Scent Detection of Cancer and Infectious Diseases With Dogs and Rats: a Systematic Review

Abstract

Background: Remote medical scent detection of cancer and infectious diseases with dogs and rats has been an increasing field of research these last 20 years. If validated, the possibility of implementing such a technique in the clinic raises many hopes. This systematic review was performed to determine the evidence and performance of such methods and assess their potential relevance in the clinic.Methods: Pubmed and Web of Science databases were independently searched based on PRISMA standards. We included studies aiming at detecting cancers and infectious diseases affecting humans with dogs or rats. We excluded studies using other animals, studies aiming to detect agricultural diseases, diseases affecting animals, and others such as diabetes and neurodegenerative diseases. Only original articles were included. Data about patients’ selection, samples, animal characteristics, animal training and testing configurations, and performances were recorded.Results: A total of 62 studies were included. Sensitivity and specificity varied a lot among studies: While some publications report low sensitivities of 17% and specificities around 29%, others achieve rates of 100% sensitivity and specificity. Only 6 studies were evaluated in a double-blind screening like situation. In general, the risk of performance bias was high in most evaluated studies, and the quality of the evidence found was low.Conclusions: Medical detection using animals’ sense of smell lacks evidence and performances so far to be applied in the clinic. What odours the animals detect is not well understood. Further research should be conducted, focusing on patient selection, samples (choice of materials, standardization), and testing conditions. Interpolations of such results to free running detection (direct contact with humans) should be taken with extreme caution.

Expert considerations and consensus for using dogs to detect human SARS-CoV-2-infections

“…In this way, specific volatile biochemical fingerprints may be detected and function as biomarkers for corresponding diseases and their clinical course, provided that appropriate sensory means are available ( 18 , 19 ). The detective olfactory potential of dogs and other animals has been researched in the medical field concerning various infectious viral, bacterial, and parasitic as well as non-infectious diseases and disorders like epilepsy, diabetes, and cancer ( 5 , 11 , 20 , 21 ). Horvath et al demonstrated that dogs can differentiate between normal and neoplastic tissue as well as non-neoplastic disease processes such as inflammation, necrosis or emergence of metabolic products ( 22 ).…”

Unraveling the potential of breath and sweat VOC capture devices for human disease detection: a systematic-like review of canine olfaction and GC-MS analysis

“…In our knowledge, there are no established applications using detection dogs in this context. The limitations of this approach are well outlined in the review by Bauer et al (Bauër et al, 2022b). These drawbacks notably include the associated high costs of employing qualified personnel for such applications, and the challenge of consistently sourcing samples for dogs' trainings, to maintain their performances over time (Bauër et al, 2022b).…”

“…One crucial factor to consider is that dogs are living beings and exhibit variability in their responses. Interpretation of canine olfaction analyzes must account for the variability among individual animals and among dog's breeds (Bauër et al, 2022b).…”

“…Nevertheless, studies in the field of analytical chemistry on the olfactory characteristics of pathologies serves as a valuable complement and may contribute to a more comprehensive understanding and standardization of experiments involving detection dogs (Bauër et al, 2022b).…”

“…Electronic nose systems are less portable than canine olfaction due to potential restrictions posed by power, weight, or space requirements (Wilson and Forse, 2023). Despite this, the use of the dog as a diagnostic tool has not yet been standardized nor validated by health organizations (Bauër et al, 2022a). Therefore, GC-MS is of great interest to identify diseases-specific VOCs, detected by dogs.…”