Prevalence and reversibility of smell dysfunction measured psychophysically in a cohort of COVID-19 patients.

ABSTRACT

BACKGROUND: Considerable evidence suggests that smell dysfunction is common in coronavirus disease-2019 (COVID-19). Unfortunately, extant data on prevalence and reversibility over time are highly variable, coming mainly from self-report surveys prone to multiple biases. Thus, validated psychophysical olfactory testing is sorely needed to establish such parameters. METHODS: One hundred severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2)-positive patients were administered the 40-item University of Pennsylvania Smell Identification Test (UPSIT) in the hospital near the end of the acute phase of the disease. Eighty-two were retested 1 or 4 weeks later at home. The data were analyzed using analysis of variance and mixed-effect regression models. RESULTS: Initial UPSIT scores were indicative of severe microsmia, with 96% exhibiting measurable dysfunction; 18% were anosmic. The scores improved upon retest (initial test mean, 21.97; 95% confidence interval [CI], 20.84-23.09; retest mean, 31.13; 95% CI, 30.16-32.10; p < 0.0001); no patient remained anosmic. After 5 weeks from COVID-19 symptom onset, the test scores of 63% of the retested patients were normal. However, the mean UPSIT score at that time continued to remain below that of age- and sex-matched healthy controls (p < 0.001). Such scores were related to time since symptom onset, sex, and age. CONCLUSION: Smell loss was extremely common in the acute phase of a cohort of 100 COVID-19 patients when objectively measured. About one third of cases continued to exhibit dysfunction 6 to 8 weeks after symptom onset. These findings have direct implications for the use of olfactory testing in identifying SARS-CoV-2 carriers and for counseling such individuals with regard to their smell dysfunction and its reversibility.