Conclusions
’ personalities
In conclusion, the sniffer dogs involved in the current study demonstrated the foundations of a good screening test: cause minimal discomfort to the human volunteers, be inexpensive to perform, easy to administer, reliable and valid in discriminating diseased and non-diseased humans. Therefore, they may be potentially useful for mass detection and contact tracing for COVID-19, being implemented in various public settings, such as schools or airports, where conventional testing is not feasible or easily accessible. Moreover, the potential usefulness of dogs could be extended to other potential health screening applications. Although, after 4 years, COVID-19 continues circulating, driven by the wildly transmissible new variants, these findings suggest that dogs could be trained and deployed as a first response to new threats or future pandemics.Sniffer dogs performed better than RAD under controlled settings but were similar to RAD in terms of sensitivity in field conditions. However, compared to RAD, sniffing dogs hold some relevant advantages: for example, they do not impose unpleasant procedures, as the nasopharyngeal/nasal swabs, thar are commonly perceived to be uncomfortable, or even painful; they provide timely identification and isolation of the largest number of patients in real-life contexts, thus improving access to communities and simplifying logistics; and do not require operators to come into direct contact with potentially infectious materials. Further efforts seeking standardisation and validation of the processes are needed to better understand the potential and limitation of using sniffing dogs for the detection of COVID-19 and verify them in appropriate populations. It is worth noticing that the consistency in error rates for positive early-stage COVID-19 between the laboratory test and in-field test was potentially the source of the increased error rates in in-field test, in addition to the change from the sweat sample to the entire body odours including clothes, cosmetics, and so on. In our study, training with diverse positive and negative volunteers, we aimed to improve the correct rates in COVID-19 detection by the sniffer dogs. Nevertheless, further research should include more high quality exploration of the influence on the odour signature (or the perception of it) by variables such as training sample number and type, sampling method, dogs’ personalities