Loss of smell should be recognised as symptom of COVID-19 _ UCL study

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Four out of five people experiencing the recent loss of smell and/or taste tested positive for COVID-19 antibodies—and of those who tested positive, 40% did not have cough or fever, reports a study by Professor Rachel Batterham at University College London and colleagues.

COVID-19 can cause loss of taste and smell, but the prevalence of COVID-19 antibodies in people reporting these symptoms is unknown, and the significance of loss of smell and/or taste as a predictor of COVID-19 is not well understood. To estimate the seroprevalence of SARS-CoV-2 antibodies in people with acute loss of their sense of smell and/or taste, researchers enrolled 590 people self-reporting a loss of taste/smell in the previous month. Following verification of symptoms via a telemedicine consultation, 567 participants with smell and/or taste loss underwent a SARS-CoV-2 antibodies test.

78% had SARS-CoV-2 antibodies, and participants with loss of smell were almost 3 times more likely to have SARS-CoV-2 antibodies compared to those with loss of taste, suggesting that a loss of smell is a highly specific symptom of COVID-19. Of the 78% of participants testing positive for antibodies, 40% had neither cough nor fever. While the study had limitations, such as the self-reporting of smell/taste changes and the lack of a control group, the researchers believe the evidence indicates that loss of smell should be taken into greater consideration in COVID-19 public health measures such as testing, case isolation, and treatment strategies.

These findings also have significant implications for policy makers globally, as most countries do not currently recommend self-isolation and testing based on acute loss of smell/taste. This study suggests that an over-reliance on cough and fever as the main symptoms of COVID-19 may be flawed and that loss of smell needs to be urgently recognized globally as a key symptom of COVID-19.

Batterham, who led the study, said “Early self-recognition of COVID-19 symptoms by the members of the public, together with rapid self-isolation and PCR testing are vital in order to limit spread of the disease. Currently, most countries around the world do not recognize sudden loss of smell as a symptom of COVID-19.

78% of participants in our community-based study with sudden onset loss of smell or taste had SARS-CoV-2 antibodies. The vast majority had mild symptoms and 40% did not report having a fever or cough. Our findings suggest that people who notice a loss in their ability to smell every day house-hold odours such as garlic, coffee and perfumes should self-isolate and seek PCR testing. Loss of sense of smell needs to be recognized globally by policy makers as a key symptom of COVID-19.

Abstract
Background: Loss of smell and taste are commonly reported symptoms associated with coronavirus disease 2019 (COVID-19); however, the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies in people with acute loss of smell and/or taste is unknown. The study aimed to determine the seroprevalence of SARS-CoV-2 antibodies in a community-based population with acute loss of smell and/or taste and to compare the frequency of COVID-19 associated symptoms in participants with and without SARS-CoV-2 antibodies. It also evaluated whether smell or taste loss are indicative of COVID-19 infection.
Methods and findings: Text messages, sent via primary care centers in London, United Kingdom, invited people with loss of smell and/or taste in the preceding month, to participate. Recruitment took place between 23 April 2020 and 14 May 2020. A total of 590 participants enrolled via a web-based platform and responded to questions about loss of smell and taste and other COVID-19–related symptoms. Mean age was 39.4 years (SD ± 12.0) and 69.1% (n = 392) of participants were female. A total of 567 (96.1%) had a telemedicine consultation during which their COVID-19–related symptoms were verified and a lateral flow immunoassay test that detected SARS-CoV-2 immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies was undertaken under medical supervision. A total of 77.6% of 567 participants with acute smell and/or taste loss had SARS-CoV-2 antibodies; of these, 39.8% (n = 175) had neither cough nor fever. New loss of smell was more prevalent in participants with SARS-CoV-2 antibodies, compared with those without antibodies (93.4% versus 78.7%, p < 0.001), whereas taste loss was equally prevalent (90.2% versus 89.0%, p = 0.738). Seropositivity for SARS-CoV-2 was 3 times more likely in participants with smell loss (OR 2.86; 95% CI 1.27–6.36; p < 0.001) compared with those with taste loss. The limitations of this study are the lack of a general population control group, the self-reported nature of the smell and taste changes, and the fact our methodology does not take into account the possibility that a population subset may not seroconvert to develop SARS-CoV-2 antibodies post-COVID-19.
Conclusions: Our findings suggest that recent loss of smell is a highly specific COVID-19 symptom and should be considered more generally in guiding case isolation, testing, and treatment of COVID-19.

Authors
Janine Makaronidis, Jessica Mok, Nyaladzi Balogun, Cormac G Magee, Rumana Z Omar, Alisia Carnemolla, Rachel L Batterham

PLOS Medicine abstract

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