| 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 |
|---|---|---|---|---|---|---|---|---|
| Talavera et al61 | Anosmia: 146/576 (25.3%) | - | Questionnaire | - | - | - | - | - |
| Yan et al62 | Anosmia/hyposmia COVID-19 admitted: 7/169 (26.9%), COVID-19 positive ambulatory: 68/169 (66.7%) | - | Medical records | - | - | - | - | - |
| Lechien et al63 | 32/86 (38.6%) Total anosmia: 61.4%, partial loss: 38.6% | - | Questionnaire | - | - | 17 | - | - |
| Barillari et al64 | Anosmia/hyposmia: 207/294 | - | Online questionnaire | Mean SNOT score-2.39±1.61 of the 5 items (parosmia, hyposmia, anosmia, phantosmia, and GD) inserted | Before 11.6%; after 57.1%; concomitant 31.3% | - | Persistence of symptoms-31.4%; 1-4 (22.2%); 5-8 (15.4%); 9-15 (24.3%). | - |
| Kim et al65 | Hyposmia: 68/172 (39.5%) | - | Questionnaire | - | - | - | - | - |
| Leedman et al66 | Anosmia/hyposmia: 36/56 (64.3%) | - | Questionnaire | UPSIT function category score Normosmia-64.3%; Mild microsmia-14.3%; Moderate microsmia-14.3%; Severe microsmia-3.5%; Anosmia-3.5% | - | - | After 6 months of COVID-19: 11 (19.6%) | - |
| Kusnik et al67 | Anosmia/hyposmia: 25/43 | - | Questionnaire | - | - | 6 | - | - |
| Makaronidis et al68 | Anosmia: 38/467 (10.0%), partial loss: 358 (93.7%), complete loss: 92 (25.7%), parosmia: 113 (29.7%) | 83.7% (319/467) | Questionnaire | - | - | - | Full resolution-206 (57.7%); no/partial resolution-151 (42.3%) | - |
| Poerbonegoro et al69 | Anosmia/hyposmia: 34/51 (66.7%) | 19/34 (55.9%) | Interview and questionnaire | VAS scores-Severe (7-10) 20 (68.9%); Moderate (4-6) 8 (27.7%); Mild (0-3) 1 (3.4%) | Before diagnosis-21/29 (72.4%); after-8/29 (27.5%) | - | - | - |
| Bayrak et al70 | Anosmia/hyposmia 56/105 (53.3%) | - | Questionnaire | VAS score-1.64±2.56 (beginning of the study) and 6.19±3.12 at the end of the second month | - | - | 31 (55.0%)-one month; 16 (28.0%)-2 months; 28.8±21.0 days | - |
| Abdelmaksoud et al71 | Total 105/134 (78.4%) Anosmia 80 (59.7%) Hyposmia 25 (18.6%) | Questionnaire | - | - | - | 7 days-zinc therapy 18 days-not received zinc therapy | Zinc therapy | |
| Goyal et al72 | 200/574 (34.84%) Hyposmia/anosmia 73 (36.5%)/115 (57.5%) Parosmia 12 (6.0%) | 163/574 (28.4%) | Questionnaire | - | First symptom-49 (24.5%) Within 7 days-136 (68.0%); between 7-14 days-15 (7.5%) | After 1 week/2 weeks/1 month/2 months/no recovery-68 (34.0%)/74 (37.0%)/33 (16.5%)/18 (9.0%)/7 (3.5%) | - |
OD: olfactory dysfunction, GD: gustatory dysfunction, COVID: coronavirus disease, SNOT: sinonasal outcome test, UPSIT: University of Pennsylvania smell identification test, VAS: visual analog scale