| Authors | Patients with OD | Patients with OD + GD | Mode of collecting data | Objective assessment of OD | Onset of OD (days) | Duration of OD (days) | Recovery time (days) | Treatment given |
|---|---|---|---|---|---|---|---|---|
| Chiesa-Estomba et al48 | Anosmia: 621/751 (83.0%), total loss: 621 (83.0%), partial loss:130 (17.0%) | - | Questionnaire | - | - | - | Complete recovery-367 (49.0%) | Nasal/oral corticosteroids-9.0%/8.0%; nasal saline irrigation-20.0% |
| Karimi-Galougahi et al49 | Anosmia: 46 (60.5%), hyposmia: 30 (39.5%) | Questionnaire | Sudden onset-63.2%; before-24; concomitant-7; after-41 | Complete/partial recovery-30.3%/44.7% | ||||
| La Torre et al50 | Isolated anosmia: 1/30 (3.3%), cases:14 (46.7%), controls: 5 (6.7%) | Cases/controls-12 (40.0%)/3 (4.0%) | Interview | - | - | - | - | - |
| Kosugi et al51 | 145/253, anosmia: 126 (86.9%), hyposmia: 19 (13.1%) | - | Online questionnaire | - | - | 15 | Full recovery-72 (52.6%); partial-46 (33.6%); no-19 (13.9%) | - |
| Gorzkowski et al52 | Anosmia: 5/229 (3.6%), permanent: 136 (97.1%), fluctuating: 4 (2.8%), parosmia: 21(15.0%), phantosmia: 17 (12.1%) | 140/229 (61.1%) | Telephone | Questionnaire-complete smell loss (0)-90 (64.3%); profound smell loss (1-3)-31 (22.1%); moderate smell loss (4-7)-19 (13.6%); mild smell loss (8-9)-0 | Concomitant-14.2%; before-77.8%; after-4.3% | - | 26 (95.7%) | - |
| Lechien et al53 | 88/88, anosmia: 35 (40.0%), hyposmia: 31 (35.0%) | - | Questionnaire | SNOT-22: 33.6±18.2; sQOD-NS: 10.8±5.5 The mean Sniffin’-Sticks test-11.14±3.2 | Concomitant-29.7%; before-21.6%; after-44.6% | 14 (25.0%); 15-30 (10.2%); 31-45 (28.4%) | - | |
| Martin Sanz et al54 | 138/215 (64.1%), hyposmia: 64.1% | - | Questionnaire | VAS score 0-2: 78 (56.5%); 3-5: 33 (23.9%); 6-8: 20 (14.4%); 7 (5.1%) | - | 10.66±0.44 | 14.0-85.4% | |
| Mazzatenta et al55 | 61/100, hyposmic: 34.0%, Severe-hyposmic: 48.0%, anosmic: 13.0% | - | Interview | - | 7.65±5.18 | - | 14 | - |
| Meini et al56 | Anosmia/hyposmia: 29/100 | 28/100 | Interview | - | - | 18 | F-26 M-14 | - |
| Mishra et al57 | Anosmia: 11/74 (14.8%) | - | Questionnaire | - | - | 21 | - | |
| Moein et al58 | Anosmia: 28/100 (28.0%) | 18/100 (18.0%) | Questionnaire | UPSIT function scores-Normosmia (31-40) 4.0%; mild microsmia (28-30) 13.0%; moderate microsmia (24-27) 24.0%; severe microsmia (17-23) 41.0%; anosmia (6-16) 18.0% | within 28 | - | ||
| Mohamud et al59 | Anosmia: 24/60 (40.0%) | - | Medical records | - | Before-5.0%; concomitant-10.0%; after-18.3%; not remember-6.7% | - | <5: 25.0%; 5-10: 5.0%; unrecovered: 10.0% | - |
| Sayin et al60 | 65/128 (51.6%), anosmia: 8 (12.5%), hyposmia: 33 (51.6%), parosmia: 11 (17.2%) | 34/64 (53.1%) | Online questionnaire | VAS score for COVID positive group-5.48±2.18 | Before/after diagnosis: 53.1%/18.8% | - |
OD: olfactory dysfunction, COVID: coronavirus disease-2019, GD: gustatory dysfunction, CCCRC: connecticut chemosensory clinical research center, UPSIT: University of Pennsylvania smell identification test, VAS: visual analog scale