Olfactory testing with Sniffin' Sticks and University of Pennsylvania Smell Identification Test in Singapore

Sniffin' sticks (SS) and the University of Pennsylvania smell identification test (UPSIT) are widely used olfactory tests, but have not yet been validated in Singapore. The primary objective of our study was to compare the performance of the unmodified SS and UPSIT in healthy adults in Singapore. The clinical implication was illustrated with a group of patients with olfactory impairment.

The SS and UPSIT were prospectively administered to healthy adults at a tertiary otolaryngology clinic from 15 May 2023 to 31 July 2023. Primary outcome measures were identification scores, 10 th percentile scores, diagnosed olfactory function, and number of unfamiliar test odours. A retrospective review of patients with olfactory impairment was then performed. We compare their diagnosed olfactory function before and after benchmarking against heathy participants' scores.

Fifty healthy participants (mean age 34 ± 9.4 years) were recruited. With SS, the mean score was 12 ± 2.5 (out of 16) and the 10 th percentile score was 10. With UPSIT, the mean score was 29.6 ± 5.8 (out of 40) and the 10 th percentile score was 25.5. The SS and UPSIT categorised 22 (44.0%) and 46 (92.0%) healthy participants as having hyposmia/anosmia, respectively. Agreement between both tests was minimal (weighted Cohen's kappa -0.020, 95% CI -0.240 to 0.101, P = 0.626). Many test odours were unfamiliar (43.8% in SS vs. 47.5% in UPSIT). Seventy-one patients with olfactory impairment were then analysed. After adjustment, 13.9% (5/36) and 25.7% (9/35) of patients who underwent SS and UPSIT, respectively, had changes in diagnosed olfactory function.

Our findings show that olfactory identification tests must be adapted and validated for the Singapore population to ensure meaningful interpretation of results.