Article Figures & Data
Figures
- Figure 1
- Preferred reporting items for systematic reviews and meta-analyses (PRISMA) flowchart.
- Figure 2
- Classification of the type of studies included in the systematic review (n=84).
Tables
Studies Study design Study location Study duration Total number of patients with COVID-19 Age (years) Male/female COVID status Kaye et al9 Pilot US Mar 2020 to Apr 2020 237 39.6±14.6 M:46 RT-PCR confirmed F:54 Klopfensteina et al20 Retrospective France Mar 2020 114 47±16 M:33.0% RT-PCR confirmed F:670% Agrawal et al21 Retrospective US Apr 2020 42 65.5 M:75.0% RT-PCR confirmed F:250% Gilania et al22 Retrospective Iran Mar 2020 to Apr 2020 8 Range: 22-44 M:25.0% RT-PCR confirmed (05/08) F:75.0% Vaira et al23 Cohort Italy Mar 2020 to Apr 2020 72 49.2 M:37.0% RT-PCR confirmed F:630% Menni et al24 Cross-sectional UK Mar 2020 1702 M:179 (+) RT-PCR confirmed (n=579) 40.79 (+) F:400 (+) 41.22 (-) M:297 (-) F:826 (-) Hopkin et al25 Observational cohort UK Mar 2020 382 40-49 M:25.4% RT-PCR confirmed (80%) F:74.6% Moein et al26 Case control Iran Mar 2020 120 (60 cases - 60 controls) 46.55 M:66.0% RT-PCR confirmed (n=60) F:340% Speth et al27 Prospective US Mar 2020 to Apr 2020 103 46.8 M:48.5% RT-PCR confirmed F:51.5% Coelho et al28 Longitudinal (cohort) US Apr 2020 220 42.8 M:21.8% RT-PCR confirmed (n=93; 42.3%) F:78.2% Roland et al29 Cohort study US Mar 2020 to Apr 2020 620 M:35.0% (+) RT-PCR confirmed (n=145) 40 (+) F:65.0% (+) 38 (-) M:22.0% (-) F:78.0% (-) Zayet et al30 Retrospective France Mar 2020 217 39.8 M:16.8% RT-PCR confirmed (n=95) F:83.2% Boscolo–Rizzo et al31 Cross-sectional Italy Mar 2020 to Apr 2020 214 - - RT-PCR confirmed (n=54) Lee et al32 Prospective cohort Korea Mar 2020 3191 46 M:37.3% RT-PCR confirmed F:62.7% Vaira et al33 Multicentre cohort Italy - 345 48.5 M:42.3% RT-PCR confirmed F:7.7% Lechien et al34 Prospective (questionnaire based survey) France - 417 36.9±11.4 M:36.9% RT-PCR confirmed F:63.1% Hopkin et al35 Online survey UK Apr 2020 2428 30-39 (median) M:27.0% RT-PCR confirmed (n=80) F:73.0% Jalessi et al36 Prospective descriptive Iran Feb 2020 to Mar 2020 100 52.94 M:67.4% RT-PCR confirmed F:32.6% Lechien et al37 Cross-sectional Spain - 16 36.0±10.1 M:50.0% RT-PCR confirmed F:50.0% Valeria et al38 Cross-sectional Italy Mar 2020 355 50 (40-59.5) M:54.0% RT-PCR confirmed F:46.0% Villarreal et al39 Descriptive observational single-centre Spain Apr 2020 230 43 (18-62) (median) M:15.0% RT-PCR confirmed F:85.0% Qiu et al40 Cross-sectional China Germany France Mar 2020 to Apr 2020 394 39 M:57.0% RT-PCR confirmed F:43.0% Tham et al41 Retrospective and cross-sectional Singapore Mar 2020 to Apr 2020 1065 34 (median) M:87.6% RT-PCR confirmed F:12.4% Naeinia et al42 Cross-sectional Iran Apr 2020 to May 2020 49 45±12.2 M:44.9% RT-PCR confirmed (n=49) F:55.1% Otte et al43 Cross-sectional Germany - 91 43.01±12.69 M:50.5% RT-PCR confirmed F:49.5% Al-Ani et al44 Retrospective Qatar May 2020 to June 2020 141 35.91±10.069 M:50.3% RT-PCR confirmed F:49.6% Altin et al45 Prospective Istanbul Mar 2020 to Apr 2020 81 54.16±16.98 M:50.6% RT-PCR confirmed F:49.4% D’Ascanio et al46 Prospective case-control US Feb 2020 to Apr 2020 43 58.1 M:67.0% RT-PCR confirmed F:33.0% Cazolla et al47 Prospective US Mar 2020 to May 2020 67 65±13.1 M:67.2% RT-PCR confirmed F:32.8% Chiesa-Estomba et al48 Prospective Belgium Mar 2020 751 41±13 M:36.4% RT-PCR confirmed F:63.6% Karimi-Galougahi et al49 Prospective cross-sectional Iran March 2020 76 38.5±10.6 M:40.8% RT-PCR confirmed F:59.2% La Torre et al50 Case control Italy March 2020 30 cases - 75 controls 43.6 M:30.7% RT-PCR confirmed (n=30) F:69.3% Kosugi et al51 Cross-sectional Brazil Mar 2020 to Apr 2020 253 36 (median) M:40.9% RT-PCR confirmed (n=145) F:59.1% Gorzkowski et al52 Cross-sectional France March 2020 229 39.7±13.7 M:35.8% RT-PCR confirmed F:64.2% Lechien et al53 Cross-sectional Australia Mar 2020 to May 2020 88 42.6±11.2 M:33.0% RT-PCR confirmed F:67.0% Martin Sanz et al54 Case-control Spain Mar 2020 to Apr 2020 Cases: 215 (60.6%) 42.9±0.67 M:9.2% RT-PCR confirmed (n=215; 60.6%) Controls: 140 (39.4%) F:80.8% Mazzatenta et al55 Cross-sectional Italy - 100 63±15 M:70.0% RT-PCR confirmed F:30.0% Meini et al202056 Cross-sectional Italy April 2020 100 65 M:60.0% RT-PCR confirmed F:40.0% Mishra et al57 Cross-sectional India - 74 17.2 M:43 RT-PCR confirmed F:31 Moein et al58 Cohort study Iran Mar 2020 to May 2020 100 45.40 (11.80; 23-76) M:67.0% RT-PCR confirmed F:33.0% Mohamud et al59 Retrospective double centre Somalia Apr 2020 60 45.7 (13.5) M:70.0% RT-PCR confirmed F:30.0% Sayin et al60 Cross-sectional Turkey - 128 (64 [+] and 64 [-]) 38.63±10.08 M:37.5% RT-PCR confirmed F:62.5% Talavera et al61 Retrospective cohort Spain Mar 2020 to Apr 2020 576 67.2 M:56.7% RT-PCR confirmed F:43.3% Yan et al62 Retrospective California Mar 2020 to Apr 2020 169 53.5 (40-65) M:34.6% RT-PCR confirmed F:65.4% Lechien et al63 Cross-sectional France - 86 41.7±11.8 M:34.9% RT-PCR confirmed F:65.1% Barillari et al64 Cross-sectional Italy Apr 2020 294 42.1±12.3 M:50.0% RT-PCR confirmed (n=179) F:50.0% Kim et al65 Cross-sectional Korea Mar 2020 172 26 (median) M:38.4% RT-PCR confirmed F:61.6% Leedman et al66 Cross-sectional Australia Nov 2020 to Dec 2020 56 55.34±16.81 M:46.4% RT-PCR confirmed F:54.6% Kusnik et al67 Cross-sectional Germany Mar 2020 to July 2020 43 (+) 41.2±16.2 (+) M:44.0% RT-PCR confirmed (n=43) 668 (-) 40.9±14.5 (-) F:66.0% Makaronidis et al68 Community based cohort UK Apr 2020 to May 2020 467 39.67±12.12 M:28.8% RT-PCR confirmed F:70.9% Poerbonegoro et al69 Cross-sectional Indonesia Nov 2020 to Dec 2020 51 30.04±1.39 M:54.9% RT-PCR confirmed F:45.1% Bayrak et al70 Cross-sectional Turkey - 105 55.9±17.6 M:50.5% RT-PCR confirmed F:49.5% Abdelmaksoud et al71 Prospective Egypt May 2020 to Aug 2020 134 47.8±15.8 M:58.2% RT-PCR confirmed F:42.8% Goyal et al72 Prospective cohort India Sep 2020 to Jan 2021 574 46.60 M:2.1% RT-PCR confirmed F:1.0% Soh et al73 Cross-sectional Singapore May 2020 to July 2020 1983 25 (median) - RT-PCR confirmed Cousyn et al74 Prospective cohort France Mar 2020 to Apr 2020 98 34.5 (27.9-47.9) M:24.5% Positive RT-PCR tests (n=96) or positive SARS-CoV-2 antibody tests (n=2) F:75.5% Bakhshaee et al75 Longitudinal Iran Mar 2020 to Apr 2020. 502 46.8±18.5 M:47.6% RT-PCR confirmed F:52.4% Sayin et al76 Cross-sectional Turkey Mar 2020 to May 2020 52 61.32±12.53 M:69.2% RT-PCR confirmed F:30.8% Printza et al77 Cross-sectional Greece Mar 2020 to Apr 2020 140 51.6±6.8 M:62.0% RT-PCR confirmed F:38.0% Kumar et al78 Prospective India May 2020 to Aug 2020 141 15.2 M:58.9% RT-PCR confirmed F:41.1% Kant et al79 Retrospective Turkey Mar 2020 to Oct 2020 8238 51.3±18.5 M:60.8% RT-PCR confirmed F:39.2% Chaturvedi et al80 Retrospective India Mar 2021 277 51.47±14.15 M:70.8% RT-PCR confirmed F:29.2% Parente-Arias et al81 Observational cohort Spain Mar 2020 151 41±12.15 M:35.1% RT-PCR confirmed F:64.9% Mubaraki et al82 Retrospective KSA May 2020 to Jul 2020 1022 15-39 M:60.9% RT-PCR confirmed F:39.1% D Silva et al83 Cross-sectional Brazil Apr 2020 166 44.7±11.6 M:65.0% RT-PCR confirmed (n=85) F:35.0% Bhatta et al84 Multicentric prospective India, Nepal, Maldives Apr 2020 to Jan 2021 188 33.1±1.7 M:54.2% RT-PCR confirmed F:45.8% Hameed et al85 Descriptive observational cross-sectional Iraq Mar 2020 to Apr 2020 35 11-60 - RT-PCR confirmed Savtale et al86 Cross-sectional India Oct 2020 180 37.8±12.5 M:33.4% RT-PCR confirmed F:66.6% Horvath et al87 Retrospective Australia Feb 2020 to Apr 2020 102 45 M:40.0% RT-PCR confirmed F:60.0% Shaikh et al88 Retrospective India Aug 2020 to Sep 2020 1070 50-59 M: 1.8 RT-PCR confirmed F:1.0 Khan et al89 Cross-sectional India Mar 2021 to Jun 2021 224 35.4±15.5 M:54.9% RT-PCR confirmed F:46.1% Lee et al90 Cross-sectional Israel and Canada Mar 2020 to Jun 2020 350 47.0 M:42.6% RT-PCR confirmed F:56.9% Others:0.6% Koul et al91 Cross-sectional India May 2020 to Aug 2020 300 37 M:74.0% RT-PCR confirmed F:26.0% Kandemirli et al92 Prospective Turkey May 2020 to Jun 2020 23 29 (median) M:39.1% RT-PCR confirmed F:60.9% Altundag et al93 Cross-sectional Turkey Mar 2020 135 39.8±11.3 M:54.8% RT-PCR confirmed F:46.2% Dev et al94 Case control India May 2020 to Jun 2020 Cases: 55 Controls: 55 36 M:58.0% RT-PCR confirmed F:42.0% Korkmaz et al95 Prospective Germany - 116 57.24±14.32 M:50.0% RT-PCR confirmed F:50.0% Babaei et al96 Retrospective Iran Dec 2020 to Mar 2021 235 43.95±15.27 - RT-PCR confirmed Nouchi et al97 Cross-sectional France Mar 2020 to Mar 2020 390 66 (median) M:64.0% RT-PCR confirmed F:36.0% Polat et al98 Cross-sectional Istanbul - 217 41.74 M:59.4% RT-PCR confirmed F:40.6% Renaud et al99 Cohort France Apr 2020 97 38.8 M:30.9% RT-PCR confirmed F:69.1% Rizzo et al100 Prospective UK - 202 57 (median) M:45.4% RT-PCR confirmed F:54.6% Thakur et al101 Prospective India Sep 2020 to Oct 2020 250 21-80 M:57.6% RT-PCR confirmed F:42.4% Teaima et al102 Prospective Egypt Aug 2020 to Oct 2020 1031 18-69 M:31.8% RT-PCR confirmed F:68.2% COVID-19: coronavirus disease - 2019, US: the United States of America, UK: the United Kingdom, KSA: Kingdom of Saudi Arabia, M: male, F: female, RT-PCR: reverse transcription-polymerase chain reaction test, (+): positive COVID-19, (-): negative COVID-19
- Table 2
- Details of olfactory dysfunction experienced by the coronavirus disease-19 positive individuals (n=84).
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 Kaye et al9 Anosmia: 173/237 (73%) - COVID-19 Anosmia reporting tool - Before: 73.0% Concomitant: 40.0% After: 27.0% 7.2±3.1 Complete recovery: 85.0% (within 10) - Klopfensteina et al20 Anosmia: 54/114 46/114 (with hypogeusia) Medical records - 4.4 8.9 7-13 (35.0%) 4-6 (30.0%) 1-3 (16.0%) 14-20 (14.0%) 21-27 (5.0%) - Agrawal et al21 - 03/42 Medical records - - - - Gilania et al22 Anosmia: 8/8 (100%) 1/8 (12.5%) (with ageusia) Medical records - After 4: 1 Sudden onset: 2 After 2: 5 - - - Vaira et al23 Mild hyposmia (70-80): 22 (30.6%) Moderate hyposmia (50-60): 33 (45.8%) Severe hyposmia (20-40): 3 (4.2%) Anosmia (0-10): 2 (2.8%) 30/72 (41.7%) Telephone CCCRC scoring system - - Within 5: 35.8% After 5: 30.2% No recovery: 34% - Menni et al24 - 342/1702 (59.0%) COVID RADAR symptom tracker app - - - - - Hopkin et al25 Anosmia: 330/382 (74.4%) Very severe: 17.3% - Email - 7 (60.0%) 7-14 21 (71.0%) - Moein et al26 Anosmia: 7/60 (12.0%) 20/60 (17.0%) Questionnaire Mean UPSIT score: (34.10, p<0.001) Anosmia: 35/60 (58.0%) Severely microsmic: 20/60 (33.0%) Moderate microsmia: 16/60 (27.0%) Mild microsmia: 8/60 (13.0%) Normosmia: 1/60 (2.0%) - - - - Speth et al27 62/103 (61.2%) Anosmia:63, Hyposmia: 14 - Telephone Mild VAS scores: 6.3% Moderate: 12.7%; severe: 81.0% 1-8.7% Mean onset: 3.4 0-12 - - Coelho et al28 22/220 (26.5%), Anosmia: 116 (56.3%) 54 (65.1%) Web-based survey - - - - - Roland et al29 Anosmia/hyposmia: 137/145 COVID - Questionnaire - - - - - Zayet et al30 Anosmia in COVID-19: 137 (63.2%)negative: 217 (14.8%) COVID-19 positive/negative-54.7%/9.0% Medical records - - - - - Boscolo-Rizzo et al31 - COVID-19: 63.0% Negative: 15.0% Telephone - - - - - Lee et al32 Anosmia: 135/3191 (27.7%) 254/3191 (52.0%) Telephone - - 7 21 - Vaira et al33 Anosmia: 22/345 (6.4%) 203 (58.8%) Telephone UPSIT function scores Hyposmia: mild-76 (22.0%), moderate-59 (17.1%), severe-45 (13.0%); and ansomia: 61 (17.7%) 14.8 ≤7: 191 (74.6%) >7: 65 (25.4%) Olfactory recovery: 70 (31.1%); normal: 21 (30%), mild hyposmia: 39 (55.7%), and moderate hyposmia: 10 (14.2%) - 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
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%) - Email - <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
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
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
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
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 Horvath et al87 66/102 (65.0%) Hyposmia-23.0%; anosmia42.0% 75/102 (74.0%) Online questionnaire - - - - - Shaikh et al88 34/1070 Hyposmia-3.2% Anosmia-7.3% 150 (14.0%) Questionnaire - - - - - Khan et al89 Anosmia/hyposmia 19/224 (8.4%) 64/224 (28.6%) Questionnaire UPSIT function scores normal-142 (63.4%); mild hyposmia 39 (17.4%); moderate hyposmia 18 (8.0%); severe hyposmia 13 (5.8%); anosmia 12 (5.4%) Within 5 days-(58/102 (56.8%) First sign-10.1% Sudden in onset-7.1% - - - Lee et al90 Anosmia-89/350 (25.4%) Hyposmia-56/350 (16.0%) - Telephone - First symptom-10% - 4 weeks (90.4%) - Koul et al91 83/231 (55.33%) Anosmia-57.3%; hyposmia-28.7% 46/231 (30.7%) Questionnaire - - - 1 month (78.0%) - Kandemirli et al92 Anosmia-23/23 - Questionnaire Sniffin’ Sticks test Threshold-1 (1±2.25); discrimination-2 (0±3); identification-3 (0±4); TDI-4 (1±8.5) Sudden onset-4/23; after-12 concomitant-07 - - - Altundag et al93 Anosmia/hyposmia-80/135 (59.3%) - Telephone VAS scores-Group 1-8.4±1.9; Group 2-7.6±2; Group 3-6.2±2.6 - 7.8±3.1 (2-15) days Group 1/2/3-28.6%/50.0%/66.7% - Dev et al94 Anosmia-53/55 (96.0%) 39 (71.0%) Medical records Mean VAS scores 5.52±2.08 7 days - 30 days Korkmaz et al95 Anosmia/hyposmia-43/116 (37.9%) - Questionnaire - - - - - Babaei et al96 Anosmia-207/235 (88.5%)-4 weeks and 219 (93.2%)-8 weeks - Interview - First symptom-23 (9.8%); Onset (mean)-3.88 day - 19.42±8.81 days - Nouchi et al97 Hyposmia 129/390 (33.0%) 106 (27.0%) Telephone - - - Persistent hyposmia-34.0% - Polat et al98 Anosmia 72/217 (33.2%) - Interview - 3 (1-13) days - 13 (3-30) days - Renaud et al99 43/51 (84.3%) Anosmia 23 (45.1%) Hyposmia 27 (52.9%) Parosmia 14 (27.5%) Phantosmia 13 (25.5%) - Questionnaire CCCRC-QOD scores ranges 0-10/11-25/26-50/51-75/76-90/91-95/96-t-5 (9.8%)/3 (5.8%)/9 (17.7%)/9 (17.7%)/13 (25.5%)/5 (9.8%)/7 (13.7%) Identification test-5 (9.8%)/5 (9.8%)/6 (11.8%)/7 (13.7%)/9 (17.7%)/9 (17.7%)/10 (19.5%)/ - - After 4 months-<15/16-30/30-60/60-90-11(47.8%)/5 (21.7%)/6 (26.1%)/1 (4.4%) - Rizzo et al100 110/202 (60.1%) Normosmia 58 (28-34) Microsmia 77 (16-27) Anosmia-10 (5-15) - Telephone CAUPSIT score-25.5; mildly microsmic-54(37.2%); moderately microsmic 16 (11.0%); severely microsmic-7 (4.8%); anosmic 10 (6.9%) - - Complete resolution/partial/no improvement 85 (77.3%)/22 (20.0%)/3 (2.7%) - OD: olfactory dysfunction, GD: gustatory dysfunction, UPSIT: University of Pennsylvania smell identification test, TDI: olfactory test, VAS: visual analog scale, CCCRC-QOD: connecticut chemosensory clinical research center - questionnaire of olfactory disorders, CAUPSIT: culturally adapted University of Pennsylvania smell identification test
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 Thakur et al101 Anosmia/hyposmia-179/250 (71.6%) - Oral questionnaire - Before-44(17.6%); after-77 (30.8%); concomitant-58(23.2%) Recovery time-1-4/5-8/9-14/more than 15 days-17 (6.8%)/87 (34.8%)/103(41.2%)/43 (17.2%) - Teaima et al102 Anosmia-67.9%; hyposmia-30.0%; phantosmia-18.0%; parosmia-28.4% Anosmia & ageusia-50.2%; hyposmia & hypogeusia-23.3% Questionnaire - After COVID symptoms-43.5% Sudden onset-80.4% After 6 months-complete/partial/no recovery-66.0%/22.1%/11.9% - OD: olfactory dysfunction, GD: gustatory dysfunction, COVID: coronavirus disease
Olfactory dysfunction category Number of studies n (%) out of 33,231patients Anosmia 29 6929 (20.8) Hyposmia 4 1676 (5.0) Anosmia or hyposmia 17 2953 (8.9) Parosmia 9 613 (1.8) Phantosmia 4 262 (0.8) Hyperosmia 2 7 (0.02) Values are presented as numbers and precentages (%).
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