Fast Olfactory Threshold Determination Using an Ascending Limits Procedure
The Sniffin’ Sticks test battery is currently considered the best alternative for the measurement of olfactory threshold, discrimination and identification capabilities. These tests still suffer from limitations, however. Most noticeably, the olfactory threshold test is an intensive task which requires participants to smell a large number of olfactory stimuli. This proves especially problematic when measuring olfactory performance of elderly patients or screening research subjects, as sensory adaptation plays an important role in olfactory perception.
In the current study, we have determined that the cause of this limitation lies with the test’s single-staircase procedure (SSP). Consequentially, we have devised an alternative ascending limits procedure (ALP). We here compared data obtained using both procedures, following a within-subject design with 40 participants. Olfactory threshold scores as well as number of trials required to complete the two procedures were investigated.
The results show that the ALP provides reliable and correct olfactory threshold ratings, as the values showed a good correlation with those obtained using the SSP and mean values did not differ significantly. Task duration, however, did show a highly significant difference, completing the SSP required participants to complete over 40% more trials compared to the ALP.
The here presented methodological improvement can save time and, more importantly, reduce participants’ cognitive and sensory strain, which is not only more comfortable, but also limits the influence of adaptation, making any measured data more reliable.
Improving standard screening methods can directly enhance the reliability of any future study using this procedure.
KeywordsSniffin’ Sticks TDI Psychophysics n-butanol Threshold
Compliance with Ethical Standards
The project was funded by a grant from the Interdisciplinary Centre for Clinical Research within the Faculty of Medicine at the RWTH Aachen University (IZKF Project N7-9).
Conflict of Interest
The authors declare that they have no conflicts of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
The study was approved by the ethics board of the Medical Faculty of the University Hospital, RWTH Aachen University.
Informed consent was obtained from all individual participants included in the study.
- Doty RL (1991) Olfactory system. Smell and taste in health and disease. Raven Press, New YorkGoogle Scholar
- Fechner TG (1860) Elemente der Psychophysik vol 1. Breitkopf und Härtel, LeipzigGoogle Scholar
- Jacob TJ, Fraser C, Wang L, Walker V, O’Connor S (2003) Psychophysical evaluation of responses to pleasant and mal-odour stimulation in human subjects: adaptation, dose response and gender differences. International Journal of Psychophysiology: Official Journal of the International Organization of Psychophysiology 48(1):67–80. https://doi.org/10.1016/S0167-8760(03)00020-5 CrossRefGoogle Scholar
- Kobal G, Hummel T, Sekinger B, Barz S, Roscher S, Wolf S (1996) “Sniffin’sticks”: screening of olfactory performance. Rhinology 34(4):222–226Google Scholar
- Wetherill G, Levitt H (1965) Sequential estimation of points on a psychometric function. Br J Math Stat Psychol 18(1):1–10. https://doi.org/10.1111/j.2044-8317.1965.tb00689.x CrossRefGoogle Scholar
- Zernecke FT, Haegler K, Albrecht J, Bruckmann H, Wiesmann M (2011) Correlation analyses of detection thresholds of four different odorants. Rhinology 49:331–336Google Scholar
- Zernecke et al (2010) Comparison of two different odorants in an olfactory detection threshold test of the Sniffin’Sticks. Rhinology 48:368–373Google Scholar