Reliability of olfactory threshold testing depends on the diversity of odor compounds

Multiple-compound mixtures of odorants are likely to produce significantly more reliable and favorable results of olfactory sensitivity testing. Within the current study we aimed to investigate this hypothesis and determine the optimal number of odor compounds within a testing stimulus. One-hundred individuals volunteered to participate in the study procedure wherein their olfactory threshold was measured with stimuli varying in the number of compounds during two sessions. We found that molecularly varied stimuli made olfactory threshold assessments relatively independent from an individual variability in sensitivity to specific odorants. Nevertheless, this was only true in certain conditions - depending on the number of components and quality of the odorants. On this basis we outline future directions for studies aimed to advance assessments of olfactory threshold by discussing the relationships between chemical and physical properties of odorants and results of the threshold assessment they produce.