Clinical Implications of Psychophysical Olfactory Testing: Assessment, Diagnosis, and Treatment Outcome

Abstract

Purpose of ReviewOlfactory dysfunction dramatically impairs quality of life with a prevalence of 20% in the general adult population. Psychophysical olfactory testing has been widely used to evaluate the ability to smell due to its validated utility and feasibility in clinic. This review summarizes the current literature regarding psychophysical olfactory testing and the clinical relevance of the olfactory testing with different components. Furthermore, the review highlights the diagnosis and treatment value of olfactory subtests in patients with olfactory dysfunction.Recent FindingsWith the accumulation of studies of psychophysical olfactory testing in olfactory disorders, the clinical relevance of olfactory testing with different components is expanding. Different olfactory domains present with distinct olfactory processing and cortical activity. Psychophysical assessment of olfaction with three domains reveals different levels of olfactory processing and might assist with analyzing the pathophysiologic mechanism of the various olfactory disorders. Furthermore, olfactory thresholds provided the largest amount of non-redundant information to the olfactory diagnosis. Sinonasal olfactory dysfunction and non-sinonasal-related olfactory dysfunction are emerging classifications of smell disorders with certain characteristics of olfactory impairment and different responses to the therapy including steroids, sinus surgery, and olfactory training.SummaryThese recent advancements should promote the understanding of psychophysical olfactory testing, the association between individual subcomponents and neurophysiological processes, and pave the way for precision assessment and treatment of the olfactory dysfunction.

What about using sniffin’ sticks 12 items test to screen post-COVID-19 olfactory disorders?

“…The most used in Europe is the Sniffin’ sticks test® (SST) [ 12 , 16 ] that includes an odor Threshold detection (T), an odor Discrimination (D), and an odor Identification (I) tests. However, these psychophysical tests are expensive and take a long time (between 30 and 60 min)) [ 10 , 11 ], thus making their daily clinical use difficult. It therefore seems important to look for other olfactory tests that are faster (≤ 5 min) and accessible to specialists, but also to general practitioners.…”

“…Although there are different ways to assess a patient's ortho and retro-olfaction [10,11], only 50% of ENTs assess the olfactory disorders on an anamnesis, and 10% assess through psychophysical tests [12]. Olfaction is most often evaluated by subjective self/hetero questionnaires with a significant variability of the results and a probable underestimation [12], given the poorer olfactory perception before 20 years and after 50 [13,14] olfactory tests, with assessment of odor threshold, odor discrimination, and odor identification, are the gold standard [12] and allow to specify the olfactory disorder [15].…”

What About Using Sniffin’ Sticks 12 Screening Test to Identify Post-Covid-19 Olfactory Disorders?

“…Although there are different ways to assess a patient’s ortho and retro-olfaction (17,18) , only 50% of ENTs assess the olfactory disorders on an anamnesis, and 10% assess through psychophysical tests (19) . Olfaction is most often evaluated by subjective self / hetero questionnaires with a significant variability of the results and a probable underestimation, (19,20) given the poorer olfactory perception before 20 years and after 50 (21,22) .…”

“…The most used in Europe is the Sniffin ‘stick test® (SST) (19,21,24–26) that include an odor Threshold detection (T), an odor Discrimination (D) and an odor Identification (I) tests. However, these psychophysical tests are expensive and take a long time (between 30 and 60 minutes)) (17,18) , thus making their daily clinical use difficult. It therefore seems important to look for other olfactory tests that are faster (≤5 minutes) and accessible to specialists, but also to general practitioners.…”

Normative data of olfactory abilities using cultural adaption Sniffin’ sticks smell test in different age groups

“…To date, many psychophysical and electrophysiological tests have been developed to quantify olfactory function in clinical settings. 8 Psychophysical tests are much more popular, as they have more practical and less technical issues than electrophysiological testing. The Sniffin’ sticks smell test is a psychophysical test developed by Hummel in 1997 and validated in several European countries.…”