ABSTRACT
BackgroundCOVID-19 has heterogeneous manifestations, though one of the most common symptoms is a sudden loss of smell (anosmia or hyposmia). We investigated whether olfactory loss is a reliable predictor of COVID-19. MethodsThis preregistered, cross-sectional study used a crowdsourced questionnaire in 23 languages to assess symptoms in individuals self-reporting recent respiratory illness. We quantified changes in chemosensory abilities during the course of the respiratory illness using 0-100 visual analog scales (VAS) for participants reporting a positive (C19+; n=4148) or negative (C19-; n=546) COVID-19 laboratory test outcome. Logistic regression models identified singular and cumulative predictors of COVID-19 status and post-COVID-19 olfactory recovery. ResultsBoth C19+ and C19-groups exhibited smell loss, but it was significantly larger in C19+ participants (mean{+/-}SD, C19+: -82.5{+/-}27.2 points; C19-: -59.8{+/-}37.7). Smell loss during illness was the best predictor of COVID-19 in both single and cumulative feature models (ROC AUC=0.72), with additional features providing negligible model improvement. VAS ratings of smell loss were more predictive than binary chemosensory yes/no-questions or other cardinal symptoms, such as fever or cough. Olfactory recovery within 40 days was reported for [~]50% of participants and was best predicted by time since illness onset. ConclusionsAs smell loss is the best predictor of COVID-19, we developed the ODoR-19 tool, a 0-10 scale to screen for recent olfactory loss. Numeric ratings [≤]2 indicate high odds of symptomatic COVID-19 (4
ABSTRACT
Aerosol droplets have emerged as the primary mode of SARS-Cov-2 transmission and can be spread by infectious asymptomatic/pre-symptomatic persons rendering indicators of latent viral infection essential. Olfactory impairment is now a recognized symptom of COVID-19 and is rapidly becoming one of the most reliable indicators of the disease. We compared olfaction data from asymptomatic students, who were assessed as SARS-CoV-2 was unknowingly spreading locally, to students tested prior to the arrival of the virus. This study was naturalistic by design as testing occurred in the context of four research studies, all of which used the same inclusion/exclusion criteria and the same protocol to objectively assess odor detection, identification, and hedonics with physiological tests. Data from students (Cohort II; N=22) with probable SARS-CoV-2 exposure were compared to students tested just prior to local virus transmission (Cohort I; N=25), and a normative sample of students assessed over the previous four years (N=272). Students in Cohort II demonstrated significantly reduced odor detection sensitivity compared to students in Cohort I (t=2.60; P=.01; d=0.77; CI, 0.17, 1.36), with a distribution skewed towards reduced detection sensitivity (D=0.38; P=.005). Categorically, the exposed group was significantly more likely to have hyposmia (OR=7.74; CI, 3.1, 19.40), particularly the subgroup assessed in the final week before campus closure (OR=13.61; CI, 3.40, 35.66;). The exposed cohort also rated odors as less unpleasant (P<.001, CLES=0.77). A limitation of our study is that participants were not tested for COVID-19 as testing was unavailable in the area. Objective measures of olfaction may detect olfactory impairment in asymptomatic persons who are otherwise unaware of smell loss. The development of cost-effective, objective olfaction tests that could be self-administered regularly could aid in early detection of SARS-CoV-2 exposure, which is vital to combatting this pandemic.
ABSTRACT
Recent anecdotal and scientific reports have provided evidence of a link between COVID-19 and chemosensory impairments such as anosmia. However, these reports have downplayed or failed to distinguish potential effects on taste, ignored chemesthesis, generally lacked quantitative measurements, were mostly restricted to data from single countries. Here, we report the development, implementation and initial results of a multi-lingual, international questionnaire to assess self-reported quantity and quality of perception in three distinct chemosensory modalities (smell, taste, and chemesthesis) before and during COVID-19. In the first 11 days after questionnaire launch, 4039 participants (2913 women, 1118 men, 8 other, ages 19-79) reported a COVID-19 diagnosis either via laboratory tests or clinical assessment. Importantly, smell, taste and chemesthetic function were each significantly reduced compared to their status before the disease. Difference scores (maximum possible change {+/-}100) revealed a mean reduction of smell (-79.7 {+/-} 28.7, mean {+/-} SD), taste (-69.0 {+/-} 32.6), and chemesthetic (-37.3 {+/-} 36.2) function during COVID-19. Qualitative changes in olfactory ability (parosmia and phantosmia) were relatively rare and correlated with smell loss. Importantly, perceived nasal obstruction did not account for smell loss. Furthermore, chemosensory impairments were similar between participants in the laboratory test and clinical assessment groups. These results show that COVID-19-associated chemosensory impairment is not limited to smell, but also affects taste and chemesthesis. The multimodal impact of COVID-19 and lack of perceived nasal obstruction suggest that SARS-CoV-2 infection may disrupt sensory-neural mechanisms.