Table 1.

Studies on the role of smell and taste disorders in suspected COVID‑19

Author source Country	Study type	No of patients	Participants	Anosmia %	Course of anosmia	Level of evidence
Giacomelli A, et al. [1] Clin Infect Dis Italy	Cross-sectional	59	SARS-CoV-2+, hospitalized	33.9% taste/smell loss 18.6% both	20.3% pre-admission anosmia	IV
Lechien et al. [2] Eur Arch Otorhinolaryngol Belgium France Italy, Spain	Case series observational	417 mild-to-moderate COVID-19	SARS-CoV-2+, hospitalized and home	85.6% smell loss 79.6% anosmic	11.8% initial symptom Taste loss in 88.8% 72.6% recovered smell in 8 d	IV
Mao L, et al. [3] JAMA Neurol China	Case series, observational	214	SARS-CoV-2+, hospitalized	5.1% 6.3% in mild disease	5.6% taste loss	IV
Beltrán-Corbellini Α, et al. [4] Eur J Neurol Spain	Case-control	79 COVID-19 40 controls	SARS-CoV-2+, hospitalized influenza controls	31.6% in COVID-19 12.5% in controls (OR 21.4)	35.5% initial symptom 35.4% taste loss 12.9% nasal obstruction 56.7% recovery (mean: 7.5 d)	III
Spinato J, et al. [5] JAMA Italy	Cross-sectional	202	SARS-CoV-2+, home	64.4%	3% only symptom 36.1% nasal obstruction	IV
Moein ST, et al. [6] Int Forum Allergy Rhinol Iran	Case–control	60 patients 60 controls	SARS-CoV-2+, hospitalized matched controls olfactory test	29% reported a loss 58% tested anosmic/severely hyposmic 18% of controls mild hyposmia	Not an initial symptom 24% taste loss	III
Yan CH, et al. [7] Int Forum Allergy Rhinol USA	Cross-sectional	59 SARS-CoV-2+ 203 SARS-CoV-2−	suspect case SARS-CoV-2+ mostly home	68% in SARS-CoV-2+ 16% in SARS-CoV-2−	Taste loss 71% in SARS-CoV-2+ 17% in SARS-CoV-2− 72.5% improvement 18% < 1 W, 37.5% 1–2 W	IV
Yan CH, et al. [8] Int Forum Allergy Rhinol USA	Case series, observational	128	SARS-CoV-2+,20% hospitalized	26.9% in hospitalized patients 66.7% in home-treated patients	Taste loss 23.1% in hospitalized vs 62.7% in home-treated Patients with loss of smell were 10 times less likely to be admitted	IV
Gudbjartsson DF, et al. [9] N Engl J Med Iceland	Epidemiological	1044	Targeted Tests SARS-CoV-2+	11.5%		High level epidemiological
Wee LE, et al. [10] Eur Arch Otorhinolaryngol Singapore	Case-control	870 suspect case 154 SARS-CoV-2+ 71 other viruses+, rhinovirus, influenza, adenoviruses, coronaviruses	Suspect cases SARS-CoV-2+ routine panel of respiratory viruses	5% in suspect cases 22.7% in SARS-CoV-2+ 2.8% in other viruses (OR 10.14)	8.6% only symptom 28.5% rhinorrhea Smell loss as screening: 98.7% specificity, 22.7% sensitivity	III
Vaira LA, et al. [11] Head Neck Italy	Case series observational	72	SARS-CoV-2+ 22 hospitalized 47 home, healthcare personnel Olfactory/taste test	73%	18% initial symptom 66% recovery at evaluation (mean 19 d) most recovered earlier than 5 d	IV
Kaye R, et al. [12] Otolaryngol Head Neck Surg USA	Online AAOHNS Reporting Tool	237 physician-submitted cases of COVID-19 related smell/taste loss	The AAOHNS COVID-19 Anosmia Reporting Tool	All	27% initial symptom 25% nasal obstruction 18% rhinorrhea Mean time to improvement of 7.2 d	IV
Hopkins C, et al. [13] Rhinology UK	Survey prompted by queries about anosmia	2428 reporting new onset anosmia	80 had been tested for SARS-CoV-2, 74% were positive	All		IV
Heidari F, et al. [14] Rhinology Iran	Anosmia case series	23	Sudden anosmia SARS-CoV-2+	All	83% initial symptom 69.6% only symptom 75% improvement in 2 weeks	IV
Gilani G, et al. [15] Medical Hypothesis Iran	Anosmia case series	8	Sudden anosmia 5 tested, SARS-CoV-2+	All	Anosmia followed other symptoms	IV
Ottaviano G, et al. [16] Rhinology Italy	Anosmia case series	6 healthcare personnel	Sudden anosmia SARS-CoV-2+	All	75% initial symptom Improvement in 15 d	IV
Gane SB, et al. [17] Rhinology UK	Anosmia case series	11	Sudden anosmia 1 tested, SARS-CoV-2+	All	55.5% only symptom	IV
Eliezer M, et al. [18] JAMA Otolaryngol Head Neck France	Case report	1	SARS-CoV-2+ CT, MRI	Anosmia without nasal obstruction	Bilateral inflammatory obstruction of the olfactory clefts	IV
Haehner A, et al. [19] medRxiv Germany	Cross-sectional controlled	500 suspect cases 34 SARS-CoV-2+ 466 SARS-CoV-2−	Suspect cases Anosmic were 22 SARS-CoV-2+ 49 SARS-CoV-2−	13.8% in all suspect cases 64.7% in SARS-CoV-2+ 10.1% in SARS-CoV-2− Anosmic pts had less severe COVID-19	4.5% initial symptom COVID-19 anosmic patients had less nasal obstruction and rhinorrhea Smell loss as screening: 65% sensitivity, 90% specificity	III
Hornuss D, et al. [20] medRxiv Germany	Cross-sectional controlled	45 patients 45 controls	SARS-CoV-2 + , hospitalized Hospitalized controls Olfactory test (Sniffin’ Stick12)	SARS-CoV-2+ 49% reported smell loss Tested anosmic 40%, hyposmic 40% 0% of controls reported anosmia		III
Levinson R, et al. [21] medRxiv Israel	Cross-sectional	42	SARS-CoV-2+ hospitalized mild COVID-19	35.7%	33.3% taste loss Anosmia follow-up/4d: 73.3% recovery, median duration 7.6 d	IV
Lechien J, et al. [22] medRxiv Belgium	Cross-sectional	78 reporting sudden anosmia 49 SARS-CoV-2+	Sudden anosmia SARS-CoV-2+ Olfactory test, 46pts	All Anosmia ≤ 12 d: 87.5% SARS-CoV-2+ Lasting: 23% SARS-CoV-2+	46.2% nasal obstruction 24% of reported anosmic patients were normosmic on olfactory testing	IV
Menni C, et al. [23] medRxiv UK	Online app Community survey For general population	1702 responders reported having being tested 579 SARS-CoV-2+ 1123 SARS-CoV-2−	Responders to RADAR COVID-19, an app asking about COVID-19 symptoms	59% in SARS-CoV-2+ 18% in SARS-CoV-2−		IV
Bagheri SHR, et al. [24] medRxiv Iran	Online community survey	10069 reporting new onset anosmia	Volunteers reporting anosmia, general population	Anosmia increased as did COVID-19 positivity in provinces of Iran		IV

No number; Level of evidence of prognostic studies; d days; w weeks; AAOHNS American Academy of Otolaryngology–Head and Neck Surgery; tested: with RT-PCR for SARS-CoV-2+