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Self-rated smell ability enables highly specific predictors of COVID-19 status: a case control study in Israel


Karni, N. ; Klein, H. ; Asseo, K. ; Benjamini, Y. ; Israel, S. ; Nimri, M. ; Olstein, K. ; Nir-Paz, R. ; Hershko, A. ; Muszkat, M. ; et al. Self-rated smell ability enables highly specific predictors of COVID-19 status: a case control study in Israel. Open Forum Infect Dis 2020.

Date Published:



Clinical diagnosis of COVID-19 is essential for detection and prevention of COVID-19. Sudden onset of taste and smell loss is a hallmark of COVID-19, and optimal ways for including these symptoms in the screening of patients and distinguishing COVID-19 from other acute viral diseases, should be established.We performed a case-control study on patients that were PCR-tested for COVID-19 (112 positive and 112 negative participants), recruited during the first wave (March 2020 – May 2020) of COVID-19 pandemic in Israel. Patients reported over by phone their symptoms and medical history and rated their olfactory and gustatory abilities before and during their illness on a 1-10 scale.Changes in smell and taste occurred in 68% (95% CI 60%-76%) and 72% (64%-80%), of positive patients, with 24 (11-53 range) and 12 (6-23) respective odds ratios. The ability to smell was decreased by 0.5±1.5 in negatives, and by 4.5±3.6 in positives. A penalized logistic regression classifier based on 5 symptoms has 66% sensitivity, 97% specificity and an area under the ROC curve of 0.83 (AUC) on a hold-out set. A classifier based on degree of smell change only is almost as good, with 66% sensitivity, 97% specificity and 0.81 AUC. The predictive positive value (PPV) of this classifier is 0.68 and negative predictive value (NPV) is 0.97.Self-reported quantitative olfactory changes, either alone or combined with other symptoms, provide a specific tool for clinical diagnosis of COVID-19. A simple calculator for prioritizing COVID-19 laboratory testing is presented here.