Sniffer Dogs as a Screening/Diagnostic Tool for COVID-19: A Proof of Concept Study

Abstract

Background: Sniffer dogs have been shown to detect certain chemical particles and help to diagnose many diseases and complications such as colorectal cancer, melanoma, bladder cancer, and even dangerous state such as hypoglycemia in DM-1 patients. With the spread of the COVID-19 throughout the world and the need to have a real time-screening of the population, especially in crowded places, we aimed to investigate the applicability of these Sniffer dogs.Methods: The study was done in two phases. In the first step, three dogs (including one German shepherd, one German black, one Labrador) were intensively trained in seven weeks by the classical conditioning method. Human specimens were obtained from the throat culture, pharyngeal secretions of both definitely positive and negative COVID-19 participants of our study. During the first seven weeks, each dog underwent the conditioning process on average about 1000 times during the course. In the verification process, 80 pharyngeal secretions samples consisting of 26 positive samples of hospitalized patients and 54 negative samples of hospitalized patients for other medical reasons and provided to the training team in a single-blind manner. The verification test was done using three dogs (Lexi, Sami, and Kozhi). Another similar conditioning process underwent using COVID-19 patients’ clothes and masks and the verification test was done using 50 positive and 70 negative samples, by three other trained dogs (one Labrador, one Border gypsy and one Golden retriever).Results: In the pharyngeal secretions verification test, the sniffer dogs could obtain 65% in sensitivity and 89% in specificity. In this process, they could identify 17 out of total 26 true positive samples and 48 out of total 54 true negative samples. According to this results, the PPV and NPV levels for this experiment were 74% and 84%, respectively. In the next verification test for face mask and clothes of patients, 43 samples were correctly identified out of 50 positive samples by dogs. Moreover, out of 70 negative samples, 65 samples were correctly found to be negative by canines. The sensitivity of this method was high as 86%, and the specificity was 92·9%. Concerning the positive and negative predictive values, the numbers are high as 89·6% and 90·3%, respectively.Conclusion: Dogs are capable of being trained as an identifier of people with COVID-19 by detecting their odor and can be used as a reliable tool in limited screening.Funding Statement: This project has been partly supported by a grant from the AJA University of Medical Sciences.Declaration of Interests: The authors have no conflict of interest to declare.Ethics Approval Statement: Ministry of Health, Treatment, and Medical Education of Iran has approved the study with the ethics code of IR.AJAUMS.REC.139.055.