| 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 |
|---|---|---|---|---|---|---|---|---|
| Lechien et al34 | 357/417 (85.6%), anosmia: 284 (79.6%); hyposmia: 73 (20.4%); phantosmia: 12.6%; and parosmia: 32.4% | Anosmia-16 (37.2%) Hyposmia-4 (9.3%) | Questionnaire | - | 9.77±5.68, before: 11.8%, after: 65.4%, concomitant: 22.8% | - | Anosmia: 1-4 (33.0%), 5-8 (39.6%), 9-14 (24.2%), and >15 (3.3%) | Oral/nasal corticosteroids: 70.0/8.0%; nasal saline irrigation: 17.0%; other: 3.0% |
| Hopkin et al35 | Anosmia: 1796/2428 (74.4%) | - | - | <7 (n=1487; 61.0%) Before-14.9%; concomitant-39.3%; after-45.8% | - | - | Nasal steroids; 20 patients; only 3-oral steroids | |
| Jalessi et al36 | 22/100 (23.9%), anosmia:9 (40.9%); hyposmia: 13 (59.1%); hyperosmia: 2 | - | Questionnaire | - | First symptom-6.5% Time of onset-3.41±2.46 | 10.73±8.26 | 21 (95.4%) | - |
| Lechien et al37 | Anosmia: 16/16 | - | Questionnaire | The mean SNOT-22 score - 28.8±18.0; mean Sniffin’ Stick score-4.6±1.7 | At presentation-100% | - | 19.8±12.8 | - |
| Valeria Dell’Era et al38 | Anosmia: 14/355 (3.9%) | 249/355 (70.0%) | Medical records and interview | Baseline smell perception of 10 (range: 3-10) | First symptom-8.7% | - | 14.0-49.5% | - |
| Villarreal et al39 | Anosmia: 157/230 (68.0%) | - | Questionnaire | Average OD-8.2 in the modified VAS (range: 2-10) | - | 11 | >28.0-26.0% | - |
| Qiu et al40 | Anosmia: 61/394 (15.0%) | 93/394 (240.0%) | Medical records | Mild-54.0%; moderate-37.0%; severe-17.0% Mean VAS score-3.60±3.62 (IQR: 0-7) The mean scores of QOD-QoL 37.0%/23.0% | - | - | - | - |
| Tham et al41 | Anosmia: 126/1065 (11.8%) | 41/1065 (3.9%) | Questionnaire | - | - | 14 | - | - |
| Naeinia et al42 | 49/49, anosmia: 42 (85.7%); hyposmia: 7 (14.3%) | - | Questionnaire | - | Sudden onset-91.8% | - | - | - |
| Otte et al43 | 41/91 (45.0%), normosmic:49, hyposmic: 41 | 80/91 (90.9%) | Questionnaire | Odour T: 6.31±0.25; odour D: 11.63±0.26; odour I: 12.92±0.21; TDI score: 30.87±0.5 | 57.94±1.40 | - | - | - |
| Al-Ani et al44 | Anosmia: 7/141 (5.0%) | 12/141 (8.5%) | Medical records | - | - | 6.89±3.056 | 3-12 | - |
| Altin et al45 | Anosmia: 29/81 (35.8%) | 20 (24.7%) | Questionnaire | - | - | - | - | - |
| D’Ascanio et al46 | 26/43, partial hyposmia: 6 (23.0%); Total anosmia: 20 (77.0%) | - | Questionnaire | - | Concomitant-07; before-04 | 5 | 30 | - |
| Cazolla et al47 | 44/67 (65.7%), anosmia: 10 (22.7%); hyposmia: 34/67 | 6 (8.9%) | Questionnaire | VAS scores: severe-38.6%; moderate-29.6%; mild-9.1% | - | 10±6 | 35 (52.2%)-14 | - |
OD: olfactory dysfunction, GD: gustatory dysfunction, SNOT: sinonasal outcome test, IQR: interquartile range, VAS: visual analog scale, T: threshold, D: discrimination, I: identification