Highly sensitive scent-detection of COVID-19 patients in vivo by trained dogs
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Abstract
Timely and accurate diagnostics are essential to fight the COVID-19 pandemic, but no test satisfies both conditions. Dogs can scent-identify the unique odors of volatile organic compounds generated during infection by interrogating specimens or, ideally, the body of a patient. After training 6 dogs to detect SARS-CoV-2 by scent in human respiratory secretions (in vitro diagnosis), we retrained 5 of them to search and find the infection by scenting the patient directly (in vivo screening). Then, efficacy trials were designed to compare the diagnostic performance of the dogs against that of the rRT-PCR in 848 human subjects: 269 hospitalized patients (COVID-19 prevalence 30.1%), 259 hospital staff (prevalence 2.7%), and 320 government employees (prevalence 1.25%). The limit of detection in vitro was lower than 10 −12 copies ssRNA/mL. During in vivo efficacy experiments, our 5 dogs detected 92 COVID-19 positive patients among the 848 study subjects. The alert (lying down) was immediate, with 95.2% accuracy and high sensitivity (95.9%; 95% C.I. 93.6–97.4), specificity (95.1%; 94.4–95.8), positive predictive value (69.7%; 65.9–73.2), and negative predictive value (99.5%; 99.2–99.7) in relation to rRT-PCR. Seventy-five days after finishing in vivo efficacy experiments, a real-life study (in vivo effectiveness) was executed among the riders of the Metro System of Medellin, deploying the human-canine teams without previous training or announcement. Three dogs were used to examine the scent of 550 volunteers who agreed to participate, both in test with canines and in rRT-PCR testing. Negative predictive value remained at 99.0% (95% C.I. 98.3–99.4), but positive predictive value dropped to 28.2% (95% C.I. 21.1–36.7). Canine scent-detection in vivo is a highly accurate screening test for COVID-19, and it detects more than 99% of infected individuals independent of key variables, such as disease prevalence, time post-exposure, or presence of symptoms. Additional training is required to teach the dogs to ignore odoriferous contamination under real-life conditions.
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SciScore for 10.1101/2021.05.30.21257913: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:This study has some limitation that deserve attention. First, there are no human coronavirus strains involved, therefore it is impossible to predict if the dogs can discriminate them from SARS-CoV-2 or, even less, from other non-human coronavirus. Since human coronavirus usually cause mild upper respiratory infections, these patients …
SciScore for 10.1101/2021.05.30.21257913: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:This study has some limitation that deserve attention. First, there are no human coronavirus strains involved, therefore it is impossible to predict if the dogs can discriminate them from SARS-CoV-2 or, even less, from other non-human coronavirus. Since human coronavirus usually cause mild upper respiratory infections, these patients rarely need hospitalization and were not part of our sample. We did find that none of the 43 hospitalized patients with respiratory conditions other than COVID-19 was positive for the dogs despite the fact that half of them had pneumonia caused by bacterial or viral pathogens like influenza virus. Second, the dogs did not have the opportunity to scent-interrogate any of the four COVID- 19 subjects from the low-risk group because they relinquished that part of the study. This prevented statistical calculations necessary to determine the size effects of the different performance metrics under very low prevalence (1.25%). The third limitation arose during dog training, and it caused the sharp decline in PPV from 69.7% to 28.2% between efficacy and effectiveness trials. To improve PPV, it is necessary to teach the dogs that there is a cut-off value in odor intensity below which they should disregard the COVID-19 scent-print. However, more research is needed to identify such threshold value and to know if it is worth to train for that, because it might be an asset to have dogs that can detect the virus immediately after a patient gets contaminated wit...
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
Results from scite Reference Check: We found no unreliable references.
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