: development of a rapid test to screen for smell loss.

Background: Commercially available smell tests are primarily used in research or in-depth clinical evaluations, but are too costly and lengthy for population surveillance in health emergencies like COVID-19. We developed the . test which rapidly evaluates three olfactory functions (detection, intensity, and identification). We tested whether self-administering the . test discriminates between individuals with smell loss or average smell ability (normosmics), and provides comparable performance as the validated and standardized NIH Toolbox Odor Identification Test in normosmics.

Methods: Using Bayesian linear models and prognostic classification algorithms, we compared the . performance of a group of self-reported anosmics (N=111, 47±13yo, F=71%,) and normosmics (N=154, 47±14yo, F=74%), as well as individuals reporting other smell disorders (e.g., hyposmia, parosmia; N=42, 55±10yo, F=67%).

Results: Ninety-four percent of normosmics met our . accuracy criteria, while only 10% of anosmics and 64% of individuals with other smell disorders did. Overall performance on . predicted belonging to the normosmic group better than identification or detection alone (vs. anosmic: AUC=0.95, Sensitivity=0.72, Specificity=0.94). Odor intensity provided the best single-feature predictor to classify normosmics. Among normosmics, 92% met the accuracy criteria at both . and the NIH Toolbox Odor Identification Test.

Conclusions: . is a practical test able to discriminate individuals with smell loss and is likely to be useful in many clinical situations, including COVID-19 symptom screening.