The Multiscent-20: A Digital Odour Identification Test Developed with Item Response Theory

Abstract Although validated and reliable psychophysical tests of olfactory function are available, an easy-to-use and feasible test has yet to be developed. This study aimed to design a digital odour identification test, evaluate its validity, establish a normative curve, and explore the impact of demographic factors. The odour identification test was presented with the Multiscent-20, a hand-held, tablet-like digital scent device that features an integrated odour digital delivery system. The identification performance on the 20 odours was assessed using item response theory (IRT). The normative curve was established by administering the test to a large sample of participants (n = 1,299). The mean identification score was 17.5 (SD = 2.1). The two-parameter logistic IRT model provided the best fit, revealing variation in item discrimination and difficulty parameters. Educational attainment influenced performance, with primary education associated with lower scores. Sex was marginally associated with performance, suggesting that men scored slightly lower than women. This study provides initial evidence supporting the validity of use of the Multiscent-20 as a digital odour identification test. The test's automation and portability enable the standardized delivery of olfactory stimuli and efficient automatic recording and scoring of responses.