Table 4.
Summary of smell-related outcomes assessed via anamnestic data collection, simple surveys and/or non-validated questionnaires
| Study authors | Patient age (years) | Setting | Olfactory evaluation(s) | Evaluation time point | Evaluation results | Olfactory dysfunction onset |
|---|---|---|---|---|---|---|
| Aggarwal et al.16 | Mean 65.5 | In-patients in single hospital | Electronic medical record database | N/A | Anosmia 3 (19%), dysgeusia 3 (19%) | N/A |
| Beltrán-Corbellini et al.17 | Average 61.6 ± 17.4 | In-patients in multiple (n = 2) tertiary care hospitals | Non-validated questionnaire | N/A | Anosmia 14 (17.7%), ageusia 14 (17.7%) | 22 (27.8%) had acute onset of olfactory &/or taste dysfunction; first symptom in 11 (13.9%) |
| Giacomelli et al.19 | Median 60; IQR 50–74 | In-patients in single tertiary care hospitals | Non-validated questionnaire (single question) | Median of 15 days after first symptoms onset | Anosmia 7 (11.9%), hyposmia 7 (11.9%) | N/A |
| Kai Chua et al.21 | N/A | Patients referred to single tertiary care hospital with acute respiratory symptoms | Non-validated questionnaire | N/A | Hyposmia 3 (9.6%), anosmia 4 (12.9%) | N/A |
| Kim et al.22 | Median 26; IQR 22–47 | Community designated for isolation of Covid-19 patients | Non-validated questionnaire survey | N/A | Of 68 individuals with hyposmia, 61 had accompanying symptoms such as hypogeusia, nasal congestion or rhinorrhoea | N/A |
| Klopfenstein et al.23 | Average 47 ± 16 (for patients with olfactory disorders only) | In-patients & out-patients in single hospital | Non-validated questionnaire (single question) | Prevalence over whole disease course | Anosmia 54 (47.4%) | Olfactory dysfunction was never first symptom; onset 4.4 days after |
| Lechien et al.27 | Mean 39.17 ± 12.09 | In-patients & out-patients | Non-validated standardised questionnaire | N/A | Loss of smell 70.2%, nasal obstruction 67.8%, rhinorrhoea 60.1%, gustatory dysfunction 54.2% | Loss of smell persisted at least 7 days after disease in 37.5% of cured patients. Mean duration of olfaction dysfunction was 8.41 ± 5.05 days |
| Lee et al.28 | Average 36.5 (range, 24.5–54.0) | Out-patients awaiting hospitalisation or facility isolation | Single question | Early stage of disease | Anosmia & ageusia in 254 of 488 (52.0%), ageusia only in 99 (20.3%), anosmia only in 135 (27.7%) | Early stage of Covid-19 |
| Luers et al.30 | Average 38 ± 13 (range, 21–87) for overall population | Out-patients in single teaching hospital | Single question | Average of 13 ± 3 days after first symptoms; 7 ± 1 after positive swab | Olfactory dysfunction 53 (73.61%) | N/A |
| Menni et al.31 | Average of 41.25 ± 12.18 in UK cohort & 44.65 ± 14.31 in US cohort | Out-patients | Self-reported symptoms – ‘COVID RADAR Symptom Tracker app’ (question on symptoms) | N/A | 64.8% in UK & 67.5% in USA had subjective olfactory &/or taste dysfunction | N/A |
| Noh et al.33 | Mean 38.0 | Patients in residential treatment centre | Single questions | N/A | 52 (26.1%) anosmia, 45 (22.6%) ageusia | Duration of anosmia ranged 2–28 days (median, 7 days) |
| Paderno et al.35 | Mean 55 ± 15 | In-patients & out-patients | Non-validated, survey-based questionnaire focusing on olfactory & gustatory dysfunctions | Mean lag time between swab & survey was 11 ± 8 days | Subjective olfactory dysfunction in 44% in hospitalised group & in 72% in home-quarantined group | Mean lag time between symptom onset & survey was 18 ± 7 days |
| Speth et al.36 | Mean 46.8 ± 15.9 | In-patients & out-patients | Non-validated standardised questionnaire | N/A | 14.6% hyposmia, 46.6% anosmia | Olfactory dysfunction was experienced on 1st day of disease by 8.7% |
| Tostmann et al.38 | N/A | Healthcare workers in single teaching hospital | Non-validated questionnaire | N/A | 37 (46.8%) subjective olfactory dysfunction | N/A |
| Trubiano et al.39 | Median 55 (IQR 46, 63.5) | Patients previously assessed in single hospital | Hospital dataset | N/A | 7 (25%) anosmia (with or without ageusia); 7 (25%) ageusia (with or without anosmia); 3 (10.7%) anosmia & ageusia | N/A |
| Wee et al.44 | N/A | In-patients & out-patients in single hospital | Non-validated questionnaire including self-reported olfactory & gustatory dysfunctions | N/A | N/A | |
| Yan et al.2 | N/A | Out-patients & in-patients in single hospital | Single question | Prevalence over whole disease course | Olfactory dysfunction in 40 | 22% reported anosmia as first symptom |
| Yan et al.45 | Median 53.5 & IQR 40–65 for in-patients; median 43 & IQR 34–54 for out-patients | Out-patients & in-patients in single hospital | Single question | Prevalence over whole disease course | olfactory dysfunction in 75 | N/A |
| Zayet et al.46 | Mean 39.8 ± 12.2 (range, 18–73) | Out-patient in single hospital | Non-validated standardised questionnaire | N/A | Dysgeusia & anosmia in 52 (54.7%), dysgeusia &/or anosmia in 70 (73.7%) | N/A |
N/A = not applicable; IQR = interquartile range; Covid-19 = coronavirus disease 2019