Using SCENTinel® to predict SARS-CoV-2 infection: insights from a community sample during dominance of Delta and Omicron variants

Abstract

Introduction: Based on a large body of previous research suggesting that smell loss was a predictor of COVID-19, we investigated the ability of SCENTinel®, a newly validated rapid olfactory test that assesses odor detection, intensity, and identification, to predict SARS-CoV-2 infection in a community sample.

Methods: Between April 5, 2021, and July 5, 2022, 1,979 individuals took one SCENTinel® test, completed at least one physician-ordered SARS-CoV-2 PCR test, and endorsed a list of self-reported symptoms.

Results: Among the of SCENTinel® subtests, the self-rated odor intensity score, especially when dichotomized using a previously established threshold, was the strongest predictor of SARS-CoV-2 infection. SCENTinel® had high specificity and negative predictive value, indicating that those who passed SCENTinel® likely did not have a SARS-CoV-2 infection. Predictability of the SCENTinel® performance was stronger when the SARS-CoV-2 Delta variant was dominant rather than when the SARS-CoV-2 Omicron variant was dominant. Additionally, SCENTinel® predicted SARS-CoV-2 positivity better than using a self-reported symptom checklist alone.

Discussion: These results indicate that SCENTinel® is a rapid assessment tool that can be used for population-level screening to monitor abrupt changes in olfactory function, and to evaluate spread of viral infections like SARS-CoV-2 that often have smell loss as a symptom.

Keywords: COVID; anosmia; hyposmia; olfaction; pandemic; prediction; testing.

Figure 1

Exclusion criteria used to determine final sample size. EDW, Electronic data warehouse.

Figure 2

Overall SCENTinel® fail rate by SARS-CoV-2 positivity rate for each SARS-CoV-2 variant. The left axis represents our sample’s biweekly C19+ rate (solid line) and SCENTinel® failure rate (dashed line). The right axis and colored bars represent the proportion of each variant in Northwestern Medical hospital samples available via the Global Initiative on Sharing Avian Influenza Data repository.

Figure 3

Heat map of correlations between C19+ and SCENTinel® test components for Delta-dominant period. All correlations greater than ±0.1 are significant at p < 0.05. All N = 693, except for the second identification attempt (Identification 2; N = 134).

Figure 4

SCENTinel® odor intensity ratings between C19+ and C19− participants during the Delta-dominant period. SARS-CoV-2 positive: mean (solid line) = 49.11, SD (dashed lines) = 35.31; SARS-CoV-2 negative: mean = 80.74, SD = 15.90; Cohen’s d = 1.16.