Olfactory function trends in COVID-19 patients: a prospective cohort study.

Background: One of the most common symptoms in COVID-19 patients is olfactory and taste dysfunction.
Aims/objectives: This study aimed to evaluate the olfactory threshold, and identification using objective tests in the Iranian population.
Material and Methods: The present study was a prospective cohort study conducted in 2020-2021 on clinically recovering COVID-19 patients. Olfactory function was evaluated at the baseline, 4-6 weeks, and 12 weeks later. Olfactory threshold assessment was performed using the Saba Sabalan kit. The Iranian version of the Pennsylvania Smell Identification Test (IR-SIT) was used for olfactory identification. The olfactory threshold was categorized as poor (<8) and good olfaction (≥8).
Results: In the present study, 111 patients were examined, including 55 men and 56 women (mean age 41.4 and 53.4 years, respectively). The mean olfactory threshold was better for men (7.2) than for women (6.6). Analysis showed age to have a negative relationship with good olfaction at baseline (OR = 0.93, p  = .05). Using IR-SIT, only 29.7% had normal olfactory function. Using linear regression, smoking was found to be significantly related to baseline IR-SIT score (adjusted Beta <0.001, p  = .03).
Conclusions and Significance: Objective tests are appropriate methods for assessing olfactory dysfunction in COVID-19 patients. Further studies are recommended.