Quantitative assessment of olfactory dysfunction accurately detects asymptomatic COVID-19 carriers


Coronavirus disease 2019 (COVID-19) is a disease caused by the SARS-CoV-2 virus. Although many people that contract COVID-19 remain asymptomatic, they may still transmit the virus. Therefore, it is important to identify these carriers to help prevent the spread of the disease. This study aimed to assess loss of smell and olfactory dysfunction in asymptomatic carriers, and to establish a precise method to quantify these parameters. The authors recorded detection in response to ten odorants at varying concentrations in normal healthy subjects and asymptomatic COVID-19 patients. The odor profiles and odor pulse kinetics were measured using Aurora Scientific’s 200B miniPID. The majority of healthy subjects could detect 80% of odorants at their second-lowest concentrations, while asymptomatic patients showed a significantly reduced ability to detect all odors at low odor concentrations. Although many patients were unaware of deficiencies in their sense of smell, it was determined that 81% had olfactory dysfunctions. At higher concentrations, healthy subjects showed a detection accuracy of 96% while asymptomatic patients showed a detection accuracy of 61%. These results suggest that olfactory dysfunctions in patients are more evident at lower odor concentrations, thus highlighting the importance of sensitive and precise testing procedures. To assess olfactory matching abilities, participants were provided two consecutive odorant stimuli. As measured by Aurora’s 200B sensor, one odor pair was similar in response amplitude while the other pair varied significantly. The participants reported whether they thought the two odorants were the same or different. Asymptomatic patients showed reduced matching skills, suggesting possible cognitive impairments in patients with COVID-19. Following further analysis, it was determined that asymptomatic patients showed significantly reduced olfactory function scores compared to normal healthy subjects. In summary, precise olfaction-based analysis identified olfactory dysfunctions in asymptomatic patients, which may have gone unrecognized using less sensitive methods and could be used as a diagnostic tool for asymptomatic carriers.