The effect of post-COVID-19 on gustatory and olfactory function: A preliminary case-controlled study

The aim of the study was to analyze objective and subjective olfactory/gustatory function in post-COVID-19 infection (PCI).

Patients with past PCR-confirmed COVID-19 infection and persistent olfactory/gustatory complaints were investigated. Olfactory threshold and identification, gustatory detection, identification, and magnitude scaling were tested.

A total of 42 PCI subjects were compared to 41 age- and gender-matched controls with no COVID-19 history. All PCI tested had mild COVID-19 disease. Mean interval between COVID-19 confirmations to testing was 7.4 ± 3.1 months. PCI subjects complained of combined dysfunction in 85.7%, isolated olfactory or gustatory dysfunction in 7.1% each. Combined complaints were significantly higher in PCI (p < 0.001). Objective testing showed significantly higher prevalence of dysfunction in PCI versus controls for hyposmia (73.8%, 12.2%), anosmia (11.9%, 0%), odor identification (68.5%, 83.0%), hypogeusia (23% and 2.4%, respectively), and impaired magnitude scaling, (p < 0.05). All PCI subjects with hypogeusia had abnormal gustatory magnitude scaling.

While most PCI subjects complained of combined gustatory and olfactory dysfunction, objective testing showed in the majority an isolated single sense dysfunction, with a low level of agreement between subjective and objective findings. Abnormal objective results for all olfactory and gustatory functions tested may suggest a central rather than peripheral mechanism, although concomitant mechanisms cannot be excluded.