Comparison of two olfactory tests in young children: A study of crayon sniffing (C-Sniff) and short U-Sniff (qU-Sniff)

This study aimed to evaluate and compare the feasibility and reliability of two olfactory tests for toddlers aged 30 to 48 months: the established short Universal Sniff (qU-Sniff) and the novel Crayon-Sniff (C-Sniff). The study included 168 toddlers aged 30 to 48 months. A primary analysis comparing the two tests regarding feasibility (completion time, dropout rates) and the influence of potential factors (age, gender, test sequence) was conducted on all participants (N = 168). The sequence of the two tests was randomized to control for order effects. Additionally, test-retest reliability was assessed in a subgroup of 56 children (the oldest age group), resulting in 224 total measurement sets for the study. Mean identification scores were comparable between the qU-Sniff (M = 1.75) and the C-Sniff (M = 1.88), p = 0.8. The C-Sniff required a significantly longer completion time (mean 352 s) than the qU-Sniff (mean 161 s, p < 0.0001). While overall dropout rates did not differ significantly between tests, younger children (30–36 months) exhibited significantly higher dropout rates for both the qU-Sniff and C-Sniff compared to older children. The order in which the tests were administered had a significant effect on completion times, but not on test scores or dropout rates. Both the qU-Sniff (ICC = 0.52) and C-Sniff (ICC = 0.539) demonstrated moderate test-retest reliability. There was no significant difference in scores between genders, and the amount of time spent in daycare had no significant effect on test performance. Both the qU-Sniff and C-Sniff are moderately reliable tools for assessing olfaction in toddlers. However, the C-Sniff is significantly more time-consuming. Future studies should consider the age-related challenges and the significant sequence effects on test duration.