Can the detection dog alert on COVID-19 positive persons by sniffing axillary sweat samples? A proof-of-concept study

Abstract

The aim of this proof-of-concept study was to evaluate if trained dogs could discriminate between sweat samples from symptomatic COVID-19 positive individuals (SARS-CoV-2 PCR positive) and those from asymptomatic COVID-19 negative individuals. The study was conducted at 2 sites (Paris, France, and Beirut, Lebanon), followed the same training and testing protocols, and involved six detection dogs (three explosive detection dogs, one search and rescue dog, and two colon cancer detection dogs). A total of 177 individuals were recruited for the study (95 symptomatic COVID-19 positive and 82 asymptomatic COVID-19 negative individuals) from five hospitals, and one underarm sweat sample per individual was collected. The dog training sessions lasted between one and three weeks. Once trained, the dog had to mark the COVID-19 positive sample randomly placed behind one of three or four olfactory cones (the other cones contained at least one COVID-19 negative sample and between zero and two mocks). During the testing session, a COVID-19 positive sample could be used up to a maximum of three times for one dog. The dog and its handler were both blinded to the COVID-positive sample location. The success rate per dog (i.e., the number of correct indications divided by the number of trials) ranged from 76% to 100%. The lower bound of the 95% confidence interval of the estimated success rate was most of the time higher than the success rate obtained by chance after removing the number of mocks from calculations. These results provide some evidence that detection dogs may be able to discriminate between sweat samples from symptomatic COVID-19 individuals and those from asymptomatic COVID-19 negative individuals. However, due to the limitations of this proof-of-concept study (including using some COVID-19 samples more than once and potential confounding biases), these results must be confirmed in validation studies.

Discrimination of SARS-CoV-2 infected patient samples by detection dogs: A proof of concept study

“…It does, however, reiterate the point raised by Edwards et al [ 23 ], that confirmed negative samples are critical. Grandjean et al [ 14 ] had a similar issue, with two of their supposed SARS-CoV-2 negative controls turned out to be positive, once they contacted the hospitals after the dogs signalled that they believed the samples were positive. With SARS-CoV-2, the false negative test rate of RT-PCR testing [ 11 ] and unknown duration of a signature odor after recovering from COVID-19, further complicate the procurement of control samples.…”

“…Dogs are able to detect VOC signatures specific to a disease from different biological fluids including urine [ 11 ] and saliva [ 12 ]. To date, there is strong evidence that there is a unique VOC profile associated with SARS-CoV-2 infection and dogs can be trained to recognize it from saliva/tracheal samples [ 13 ] and sweat samples [ 14 ]. Jendrny et al [ 13 ] trained eight detection dogs over one week to discriminate between SARS-CoV-2 positive and negative saliva and tracheal secretion samples.…”

“…In the double-blind experiment with seven novel SARS-CoV-2 positive and seven novel SARS-CoV 2 negative samples, though the samples were initially novel, they were presented repeatedly and the data are reported together, making it more difficult to discuss the dogs’ true ability to generalize to completely novel samples. Grandjean et al [ 14 ] trained six detection dogs discriminate between SARS-CoV-2 positive and negative axillary sweat samples, and similarly utilized repeated presentation of samples to the dogs, though they did not find that the success rates were lower on initial presentation of SARS-CoV-2 positive samples (the same information for SARS-CoV-2 negative samples was not included).…”

Scent dog identification of SARS-CoV-2 infections, similar across different body fluids

“…Clostridium difficile or mastitis causing pathogens 16,17 , hypoglycaemia in diabetics 18 , and virus infections in cell cultures 12,19 . In addition, several research groups worldwide currently train and deploy SARS-CoV-2 detection dogs 20,21 . In a pilot study, our group showed that dogs were able to detect inactivated saliva samples from COVID-19 patients with a sensitivity of 83% and specificity of 96% 22 , which has been confirmed by other groups training dogs to detect either respiratory secretions or sweat samples from COVID-19 patients 20,21 .…”

“…In addition, several research groups worldwide currently train and deploy SARS-CoV-2 detection dogs 20,21 . In a pilot study, our group showed that dogs were able to detect inactivated saliva samples from COVID-19 patients with a sensitivity of 83% and specificity of 96% 22 , which has been confirmed by other groups training dogs to detect either respiratory secretions or sweat samples from COVID-19 patients 20,21 . Despite these preliminary promising results, it remains to be shown whether dogs detect VOCs which are biofluid-specific or alternatively there is a more general change in odour of COVID-19 patients.…”