Table 3.

Overview of previous studies [9, 13–16, 35]

Study	Method of chemosensory assessment	Population, n (mean age, years)	Follow-up time, mean (days)	Olfactory function at follow-up	Gustatory function at follow-up
Chiesa-Estomba et al. [35]	Prospective, survey-based, telemedicine	751 (41)	47.7	Full recovery: 49%; improvement: 14%; no improvement: 37%
Vaira et al. [9]	Connecticut Chemosensory Clinical Research Center orthonasal olfaction test (hospitalized patients) or self-administered olfactory and gustatory psychophysical test (home-quarantined patients)	138 (51.2)	60	5.8% with severe dysfunction	4.3% with severe dysfunction
Amer et al. [13]	Prospective, questionnaire-based	96 (34.3)	30	Full recovery: 33.3%; improvement: 41.7%; no improvement: 25%
Brandão Neto et al. [14]	Prospective, interview-based	655 (37.7)	76	Full recovery: 53.8%; partial improvement: 44.7%; no improvement: 1.4%	Full recovery: 68.3%; partial improvement: 27.6%; no improvement: 4.1%
Otte et al. [16]	Olfaction was tested using Sniffin' Sticks (Burghart Messtechnik GmbH, Wedel, Germany), and gustation was tested using taste sprays	91 (43.01)	57.9	Hyposmia: 45.1%; normal range: 53.8%
Iannuzzi et al. [15]	Sniffin' Sticks (Burghart Messtechnik GmbH, Wedel, Germany)	30 (47.5)	˜55	27% remained hyposmic; no patients remained anosmic

Only studies that have looked into improvement and recovery from COVID-19-related chemosensory dysfunction with follow-up times of more than 1 month were included.