| 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 |
|---|---|---|---|---|---|---|---|---|
| Soh et al73 | Anosmia-59/1938 (3.0%) Symptomatic-34 (4.4%) Asymptomatic-25 (2.1%) | - | Questionnaire | - | - | - | - | - |
| Cousyn et al74 | 95/98 (97%) Hyposmia-9/95 (96.9%); anosmia-86/95 (90.5%); parosmia-6/95 (6.3%); phantosmia-15/95 (15.8%) | Telephone | - | 2 days before COVID-19 diagnosis | - | 20 days | - | |
| Bakhshaee et al75 | 173/502 (37.9%) Anosmia-108 (22.0%) Hyposmia-94 (19.1%) Parasmia-17 (3.7%) Hyperosmia-5 (1.1%) | Medical records | VAS scores-2.5±2.5; 8.3±2.1; and 9.4±1.6 at the first evaluation, in 2 weeks, and after 1 month of follow-up (p<0.001) | Sudden-71 (60.2%); gradual-47 (39.8%); concomitant-72 (51.1%) | - | After 2 weeks in 18 (25.3%) anosmic and 37 (46.8%) hyposmic | - | |
| Sayin et al76 | 03/52 Hyposmia-18 (85.78%); anosmia-3 (14.28%) | 18/52 | Questionnaire | - | Before ICU stay-15 (68.2%) | - | - | - |
| Printza et al77 | Anosmia/hyposmia-57/140 (41%) | 48/140 (34.0%) | Telephone | VAS scores-mild-3 (5.0%); moderate-12 (21.0%); severe-11 (19.0%); extremely severe (anosmia)-31 (54.0%) | First symptom-15 (26.0%) | 11.5±13.3 days | Recovery-50 (88.0%)-61 days Median recovery time-10 days | - |
| Kumar et al78 | 12/141 Hyposmia-16/141 Anosmia-18/141 | 28/141(19.8%) | Questionnaire | - | First symptom-13.5% | 2-15 days | Within 7 days; After 15 days-3 patients | - |
| Kant et al79 | Anosmia/hyposmia 1756/8238 (21.3%) | - | Questionnaire | - | 2.9±2.3 days after the onset of COVID-19 | 9.4±2.7 days | Improved 2-5 days-78.1% Within 14 days-16.2%; after 14 days-3.2% | - |
| Chaturvedi et al80 | Anosmia/hyposmia 130/277 (47.7%) | 153/277 (55.0%) | Telephone | - | With other symptoms-58.2% | - | 5-10 days (64.1%); <5 days-34.8% >14 days-11.1% | - |
| Parente-Arias et al81 | 8/151 (8.1%) Anosmia-75/151 (49.7%) Hyposmia-26 (17.2%) Isolated anosmia-2 (1.3%) | 99/151 (65.6%) | Telephone | - | Same day-19/75 (25.3%) | 4.4±0.6 days | First 2 months (85.3%) | - |
| Mubaraki et al82 | 541/1022 (53.0%) Anosmia-32.7%; hyposmia-20.3% | - | Telephone | - | - | Anosmia/hyposmia-12.1±10.3/8.7±8.3 | - | - |
| D Silva et al83 | 45/166 (53.0%) Hyposmia-45 (53.0%) | - | Online questionnaire | 8.3±4.7 days | ||||
| Bhatta et al84 | 112/188 (60.6%) Hyposmia-36.1%; anosmia-20.2%; parosmia-4.2% | - | Questionnaire | - | - | Hyposmia/anosmia/parosmia-8/5/2 days | After 4 months Anosmia-97.4%; hyposmia-95.6%; parosmia-100% | - |
| Hameed et al85 | 4/35 Anosmia-4 Anosmia and hypogeusia-2 | 2/35 | Questionnaire | - | - | 7-14 days | - | - |
| Savtale et al86 | Anosmia/hyposmia-90/180 (55.5%) | - | Verbal survey | - | - | 20.5 days | - | - |
OD: olfactory dysfunction, GD: gustatory dysfunction, COVID: coronavirus disease, VAS: visual analog scale, ICU: intensive care unit