Background

Rapid spread of the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) and concern for viral transmission by ambulatory patients with minimal to no symptoms underline the importance of identifying early or subclinical symptoms of coronavirus disease 2019 (COVID-19) infection. Two such candidate symptoms include anecdotally reported loss of smell and taste. Understanding the timing and association of smell/taste loss in COVID-19 may help facilitate screening and early isolation of cases.

Methods

A single-institution, cross-sectional study evaluating patient-reported symptoms with a focus on smell and taste was conducted using an internet-based platform on adult subjects who underwent testing for COVID-19. Logistic regression was employed to identify symptoms associated with COVID-19 positivity.

Results

A total of 1480 patients with influenza-like symptoms underwent COVID-19 testing between March 3, 2020, and March 29, 2020. Our study captured 59 of 102 (58%) COVID-19-positive patients and 203 of 1378 (15%) COVID-19-negative patients. Smell and taste loss were reported in 68% (40/59) and 71% (42/59) of COVID-19-positive subjects, respectively, compared to 16% (33/203) and 17% (35/203) of COVID-19-negative patients (p < 0.001). Smell and taste impairment were independently and strongly associated with COVID-19 positivity (anosmia: adjusted odds ratio [aOR] 10.9; 95% CI, 5.08-23.5; ageusia: aOR 10.2; 95% CI, 4.74-22.1), whereas sore throat was associated with COVID-19 negativity (aOR 0.23; 95% CI, 0.11-0.50). Of patients who reported COVID-19-associated loss of smell, 74% (28/38) reported resolution of anosmia with clinical resolution of illness.

Conclusion

In ambulatory individuals with influenza-like symptoms, chemosensory dysfunction was strongly associated with COVID-19 infection and should be considered when screening symptoms. Most will recover chemosensory function within weeks, paralleling resolution of other disease-related symptoms.

The association of smell and taste loss with COVID-19 has been well demonstrated with high prevalence rates. In certain cases, chemosensory loss may be the only symptom of COVID-19 and may linger while other symptoms have resolved. The significance of persistent smell and taste loss and its relationship to ongoing viral shedding has yet to be investigated. In this cross-sectional study, of the 316 laboratory test-confirmed COVID-19 cases at our institution, 46 had subsequent test-based confirmation of viral clearance with 2 consecutive negative RT-PCR test results (reverse transcriptase polymerase chain reaction). Olfactory dysfunction was reported by 50% of the patients (23 of 46), with 78% (18 of 23) having subjective persistent smell loss despite negative RT-PCR test results. These preliminary data demonstrate the persistence of self-reported smell loss despite otherwise clinical resolution and undetectable nasal viral RNA.

Background

Rapid spread of the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) virus has left many health systems around the world overwhelmed, forcing triaging of scarce medical resources. Identifying indicators of hospital admission for coronavirus disease 2019 (COVID-19) patients early in the disease course could aid the efficient allocation of medical interventions. Self-reported olfactory impairment has recently been recognized as a hallmark of COVID-19 and may be an important predictor of clinical outcome.

Methods

A retrospective review of all patients presenting to a San Diego Hospital system with laboratory-confirmed positive COVID-19 infection was conducted with evaluation of olfactory and gustatory function and clinical disease course. Univariable and multivariable logistic regression were performed to identify risk factors for hospital admission and anosmia.

Results

A total of 169 patients tested positive for COVID-19 disease between March 3 and April 8, 2020. Olfactory and gustatory data were obtained for 128 (75.7%) of 169 subjects, of which 26 (20.1%) of 128 required hospitalization. Admission for COVID-19 was associated with intact sense of smell and taste, increased age, diabetes, and subjective and objective parameters associated with respiratory failure. On adjusted analysis, anosmia was strongly and independently associated with outpatient care (adjusted odds ratio [aOR] 0.09; 95% CI, 0.01-0.74), whereas positive findings of pulmonary infiltrates and/or pleural effusion on chest radiograph (aOR 8.01; 95% CI, 1.12-57.49) was strongly and independently associated with admission.

Conclusion

Normosmia is an independent predictor of admission in COVID-19 cases. Smell loss in COVID-19 may be associated with a milder clinical course.

BACKGROUND: The clinical course of coronavirus disease 2019 (COVID-19) olfactory dysfunction remains poorly characterized, often limited by self-reported measures. Given the logistical challenges of psychophysical testing, understanding the longitudinal relationship between self-reported and quantitative measures can help accurately identify patients with persistent olfactory dysfunction. This study aimed to longitudinally correlate measured and subjective olfactory function in COVID-19 subjects. METHODS: A prospective, longitudinal study evaluating subjective and measured olfaction was conducted on ambulatory COVID-19 subjects. Olfaction scores were obtained using a visual analogue scale (VAS) (0 = anosmia, 10 = normosmia) and the validated 12-item Brief Smell Identification Test (BSIT). Weekly testing was performed until recovery (BSIT ≥ 9/12 and/or VAS = 10/10) or study completion. RESULTS: Eighty-six polymerase chain reaction (PCR)-positive COVID-19 subjects were recruited ≤3 days from diagnosis and 52 completed longitudinal testing. Among those with self-reported smell loss at recruitment, similar levels (75.8%) of objective (BSIT ≥ 9/12) and subjective recovery were obtained using a VAS cutoff ≥8, yet only 30.3% reported complete subjective recovery (VAS = 10). Median times to objective and complete subjective olfactory recovery were 12 ± 2.3 and 24 ± 3.5 days, respectively. Although both measures showed chemosensory improvement, the distributions of objective and full subjective olfactory recovery differed significantly (log rank test χ2 = 6.46, degrees of freedom [df] = 1, p = 0.011). Overall correlation between BSIT and VAS scores was moderate to strong across longitudinal follow-up (rs = 0.41-0.65). CONCLUSION: Self-reported and psychophysically measured COVID-19 olfactory dysfunction improve at similar levels and are moderately correlated longitudinally, yet there is a significant delay in complete subjective recovery. Psychophysical testing in conjunction with qualitative assessments may be considered for counseling and follow-up of patients with COVID-19 smell loss.

Through multiple cell-cell and cell-matrix interactions, epithelial and endothelial sheets form tight barriers. Modulators of the cytoskeleton contribute to barrier stability and act as rheostats of vascular permeability. In this study, we sought to identify cytoskeletal regulators that underlie barrier diversity across vessels. To achieve this, we correlated functional and structural barrier features to gene expression of endothelial cells (ECs) derived from different vascular beds. Within a subset of identified candidates, we found that the guanosine nucleotide exchange factor Vav3 was exclusively expressed by microvascular ECs and was closely associated with a high-resistance barrier phenotype. Ectopic expression of Vav3 in large artery and brain ECs significantly enhanced barrier resistance and cortical rearrangement of the actin cytoskeleton. Mechanistically, we found that the barrier effect of Vav3 is dependent on its Dbl homology domain and downstream activation of Rap1. Importantly, inactivation of Vav3 in vivo resulted in increased vascular leakage, highlighting its function as a key regulator of barrier stability.

Metastases largely rely on hematogenous dissemination of tumor cells via the vascular system and significantly limit prognosis of patients with solid tumors. To colonize distant sites, circulating tumor cells must destabilize the endothelial barrier and transmigrate across the vessel wall. Here we performed a high-content screen to identify drugs that block tumor cell extravasation by testing 3,520 compounds on a transendothelial invasion coculture assay. Hits were further characterized and validated using a series of in vitro assays, a zebrafish model enabling three-dimensional (3D) visualization of tumor cell extravasation, and mouse models of lung metastasis. The initial screen advanced 38 compounds as potential hits, of which, four compounds enhanced endothelial barrier stability while concurrently suppressing tumor cell motility. Two compounds niclosamide and forskolin significantly reduced tumor cell extravasation in zebrafish, and niclosamide drastically impaired metastasis in mice. Because niclosamide had not previously been linked with effects on barrier function, single-cell RNA sequencing uncovered mechanistic effects of the drug on both tumor and endothelial cells. Importantly, niclosamide affected homotypic and heterotypic signaling critical to intercellular junctions, cell-matrix interactions, and cytoskeletal regulation. Proteomic analysis indicated that niclosamide-treated mice also showed reduced levels of kininogen, the precursor to the permeability mediator bradykinin. Our findings designate niclosamide as an effective drug that restricts tumor cell extravasation through modulation of signaling pathways, chemokines, and tumor-endothelial cell interactions. SIGNIFICANCE: A high-content screen identified niclosamide as an effective drug that restricts tumor cell extravasation by enhancing endothelial barrier stability through modulation of molecular signaling, chemokines, and tumor-endothelial cell interactions. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/3/619/F1.large.jpg.