Table 3.
Cohort Studies on Olfactory Disturbances in COVID-19 Patients
| Author | Country | Sample Size | Primary Outcome(s) | Methods of Olfactory Assessment | Prevalence of Olfactory Impairment (%) | Female (%) | Proposed Etiology of Olfactory Impairments |
|---|---|---|---|---|---|---|---|
| Beltrán-Corbellini et al [31] | Spain | 79 | Smell and taste disorder | Questionnaire | 25/79 (31%) | 31/79 (39%) | Damage of the olfactory sensory epithelium |
| Bénézit et al [23] | France | 68 | Hyposmia and hypogeusia | Questionnaire | 31/68 (45%) | Not reported | Pathology at the olfactory mucosa |
| Burrer et al [9] | USA | 4707 | COVID-19 in healthcare workers | Consultation | 750/4707 (16%) | Not reported | Nil |
| Giacomelli et al [27] | Italy | 59 | Olfactory and taste disorders | Questionnaire | 14/59 (24%) | 19/59 (32%) | Transneural penetration through the olfactory bulb |
| Heidari et al [33] | Iran | 23 | Anosmia | Consultation | 23/23 (100%) | 15/23 (65%) | Nil |
| Klopfenstein et al [20] | France | 114 | Anosmia | Consultation | 54/114 (47%) | 36/54 (67%) | Nil |
| Lechien et al [7] | Europe (Belgium, France, Italy, Spain) | 417 | Olfactory and gustatory dysfunctions | Questionnaire | 357/417 (86%) | 263/417 (63%) | Viral invasion through ACE2 receptor to olfactory bulb or related regions of CNS |
| Lytras et al [28] | Greece | 40 | Prevalence of COVID-19 in repatriation flights to Greece | Consultation | 2/5 (40%) | Not reported | Nil |
| Mao et al [8] | China | 214 | Neurologic manifestation | Consultation | 11/214 (5%) | 127/214 (59%) | Retrograde neuronal invasion |
| Marzano et al [24] | Italy | 22 | COVID-19 associated skin manifestation | Consultation | 4/22 (18%) | 6/22 (27%) | Nil |
| Moein et al [21] | Iran | 60 | Olfactory dysfunction | UPSIT | 59/60 (98%) | 20/60 (33%) | Damage of the olfactory epithelium |
| Monti et al [26] | Italy | 4 | Clinical characteristics of immunosuppressed patients with chronic arthritis | Consultation | 3/4 (75%) | 4/4 (100%) | Nil |
| Spinato et al [32] | Italy | 202 | Alterations in smell or taste | Questionnaire | 130/202 (64%) | 105/202 (52%) | Nil |
| Toscano et al [29] | Italy | 5 | Guillain-Barré syndrome associated with SARS-CoV-2 | Consultation | 2/5 (40%) | 1/5 (20%) | Nil |
| Wolfel et al [30] | Germany | 9 | Virologic manifestations | Self-reported through consultation | 3/9 (33%) | Not reported | Not suggested |
| Yan et al [4] | USA | 59 | Chemosensory dysfunction | Questionnaire | 40/59 (68%) | 29/59 (49%) | Pathology at the olfactory epithelium |
| Zayet et al [25] | France | 62 | Anosmia and dysgeusia | Consultation | 32/62 (52%) | 38/62 (61%) | Nil |
Abbreviations: CNS, central nervous system; COVID-19, coronavirus disease 2019; SARS-COV-2, severe acute respiratory syndrome coronavirus 2; UPSIT, University of Pennsylvania Smell Identification Test.