Self-reported olfactory and gustatory dysfunction and psychophysical testing in screening for COVID-19: A systematic review and meta-analysis

Background: A substantial proportion of coronavirus disease-2019 (COVID-19) patients demonstrate olfactory and gustatory dysfunction (OGD). Self-reporting for OGD is widely used as a predictor of COVID-19. Although psychophysical assessment is currently under investigation in this role, the sensitivity of these screening tests for COVID-19 remains unclear. In this systematic review we assess the sensitivity of self-reporting and psychophysical tests for OGD.

Methods: A systematic search was performed on PubMed, EMBASE, and ClinicalTrials.gov from inception until February 16, 2021. Studies of suspected COVID-19 patients with reported smell or taste alterations were included. Data were pooled for meta-analysis. Sensitivity, specificity, and diagnostic odds ratio (DOR) were reported in the outcomes.

Results: In the 50 included studies (42,902 patients), self-reported olfactory dysfunction showed a sensitivity of 43.9% (95% confidence interval [CI], 37.8%-50.2%), a specificity of 91.8% (95% CI, 89.0%-93.9%), and a DOR of 8.74 (95% CI, 6.67-11.46) for predicting COVID-19 infection. Self-reported gustatory dysfunction yielded a sensitivity of 44.9% (95% CI, 36.4%-53.8%), a specificity of 91.5% (95% CI, 87.7%-94.3%), and a DOR of 8.83 (95% CI, 6.48-12.01). Olfactory psychophysical tests analysis revealed a sensitivity of 52.8% (95% CI, 25.5%-78.6%), a specificity of 88.0% (95% CI, 53.7%-97.9%), and a DOR of 8.18 (95% CI, 3.65-18.36). One study used an identification test for gustatory sensations assessment.

Conclusion: Although demonstrating high specificity and DOR values, neither self-reported OGD nor unvalidated and limited psychophysical tests were sufficiently sensitive in screening for COVID-19. They were not suitable adjuncts in ruling out the disease.