Olfactory function and viral recovery in COVID-19

Olfactory and taste disorders were reported in up to 30%-80% of COVID-19 patients. The purpose of our study was to objectively assess smell impairment in COVID-19 patients and to correlate olfactory function with viral recovery.

Between 15 and 30 April 2020, hospitalized patients with confirmed SARS-CoV-2 infection underwent an objective assessment of olfactory function with the Smell Identification subtest of the Sniffin' Sticks Test (SI-SST). Association between viral recovery and SI-SST performance was evaluated.

51 patients were enrolled (49% males, mean age 66.2 ± 14.6 years). At the time of test administration, 45% were clinically recovered and 39% were virus-free. Objective hyposmia/anosmia was found in 45% of the patients. Subjective olfactory disorders showed no association with the clinical or viral recovery status of the patients. On the contrary, none of the patients with anosmia and the 5% of hyposmic patients at test had viral recovery. The relative risk for hyposmic patients to be still positive at swab test was 10.323 (95% CI 1.483-71.869, p < .0001). Logistic regression analysis showed an independent and significant correlation between viral clearance and SI-SST scores (OR = 2.242; 95% CI 1.322-3.802, p < .003). ROC curve analysis confirmed that a SI-SST > 10.5 predicts viral clearance with 79% sensitivity and 87% specificity (AUC = 0.883).

Hyposmia is part of COVID-19 symptoms; however, only objectively assessed olfactory function is associated with viral recovery. SI-SST is an easy and safe instrument, and further large multicentric studies should assess its value to predict infection and recovery.