Table III.

Features of the studies using imaging techniques.

Source		Year	Country	Study population	Methods	Prevalence	Recovery time	Topic	STROBE score*
1	Altundag A 71	2020	Turkey, USA	91 cases: 24 cases COVID-19 patients, 38 patients with PIOD, and a control group of 29 patients	CT scan, MRI	COVID-19 patients: 100% anosmic	N/A	Radiological study	22
2	Kandemirli SG 72	2021	Turkey, USA	23 COVID-19 patients	Sniffin’ sticks, CT scan, MRI	COVID-19 patients: 100% anosmic	N/A	Radiological study	20
3	Lechien JR 73	2020	Multicentric	16 COVID-19 patients	Validated questionnaire, Sniffin’ sticks, olfactory cleft examination, CT scan	COVID-19 patients: 100% anosmic	N/A	Radiological study	22
4	Tekcan Sanli DE 74	2021	Turkey, USA	50 COVID-19 patients	Sniffin’ sticks, CT scan.	N/A	N/A	Radiological study	21
5	Yildirim D 75	2021	Turkey, USA	31 COVID-19 patients, 97 patients with PIOD	Olfactory bulb MRI, DTI, and olfactory fMRI	COVID-19 patients: 100% anosmic; PIOD patients: 18.6% hyposmic, 81.4% anosmic	N/A	Radiological study	21

PIOD: indicates post-infectious olfactory disorder; CT: computed tomography; MRI: magnetic resonance imaging; N/A: not applicable.

*Scores interval from 0 to 22, with higher scores showing better study quality ¹².