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With a wide range of symptoms and varying degrees of severity, COVID-19 can be epidemiologically difficult to track. The fact that potentially infected individuals with mild or no symptoms are often not tested can lead to greater spread, making the identification of diagnostic markers––traits that indicate the possibility of infection in an individual–– essential for managing the pandemic. Olfactory dysfunction (OD), or a reduced or distorted ability to smell, has been suggested as a possible diagnostic marker for COVID-19. To investigate the validity of this claim, researchers in the UK performed a meta analysis, aggregating results of previous papers on COVID-19.
The researchers focused on the results of 12 studies that showed evidence of a link between COVID-19 and OD, and used statistical models to test how effective OD is as an indicator of COVID-19. They found that patients who tested positive for COVID-19 had a 62% prevalence of OD, and reported a positive predictive value of 61%, indicating that patients with OD have a 61% chance of having COVID-19. Compared to other symptoms that point to COVID-19, the authors found that OD is comparatively more predictive, and recommend that those who develop OD self-isolate.