High Test-Retest Reliability of the Extended Version of the "Sniffin' Sticks" Test

Abstract

The "Sniffin' Sticks" test kit is a validated and commonly used tool for assessment of olfactory function in subjects with normal sense of smell and in individuals with smell loss. That test incorporates subtests for odor threshold, discrimination, and identification. To gain higher subtest reproducibility, tests on odor discrimination and odor identification were extended using 32 instead of the usually applied 16 single trials each. In developing the extended Sniffin' Sticks test, a number of preliminary experiments were performed in 46 healthy, normosmic individuals 1) to evaluate intensity and familiarity of the additionally selected odors, 2) to select distractors for the discrimination and identification test, and 3) to evaluate the test-retest reliability of each subtest. Furthermore, the extended test was applied to 126 patients with olfactory loss and 71 normosmic individuals. Follow-up investigation could be performed in 69 controls within an average interval of 4 days. Results revealed significant differences between patients and healthy subjects. Estimated intensity and familiarity of the newly selected 16 items of the discrimination test did not differ significantly from the 16 standard items. Test-retest reliability was found to be r = 0.80 (odor discrimination), r = 0.88 (odor identification), and r = 0.92 (odor threshold). In conclusion, the extended test kit allows a precise evaluation of olfactory function, especially when different olfactory tasks are assessed using individual subtests. Furthermore, the high test-retest reliability of both the 16 and the 32-item tests allows the evaluation of even relatively small changes of olfactory function over time by means of either test.

High false positive rates in common sensory threshold tests

“…The reliability of human sensory threshold tests for olfaction and gustation is often low (Doty et al, 1995;Lawless, Thomas, & Johnston, 1995;Stevens et al, 1995;Stevens & Dadarwala, 1993). While some studies indicate test-retest correlation coefficients of staircase methods for olfactory thresholds above 0.8 (Lotsch et al, 2004;Doty et al, 1995;Haehner et al, 2009), others demonstrate coefficients in the range of 0.6-0.7, with even lower correlations over longer periods of time (Linschoten et al, 2001). Taste thresholds often show test-retest coefficients around 0.6 or less (McMahon et al, 2001;Stevens et al, 1995;Linschoten et al, 2001).…”

“…Typical methods for dealing with the false thresholds have included correcting for the proportion of expected "guessers," which can be done at each concentration step or across the ranges of concentrations; or fitting psychometric functions to the data, which assumes a certain rate of false positives. Experiments comparing methods of threshold testing acknowledge that multiple tests, or even multiple methods, will give the most reliable data regarding an individual's true range of sensitivity, as the variance both among and within subjects in these datasets are high (Boesveldt, de Muinck Keizer, Knol, Wolters, & Berendse, 2009;Doty, McKeown, Lee, & Shaman, 1995;Doty, Smith, McKeown, & Raj, 1994;Haehner et al, 2009;Lotsch, Lange, & Hummel, 2004;Stevens, Cruz, Hoffman, & Patterson, 1995;. However, comparative data among a variety of testing methods are limited, and most naturally data arise from actual experiments designed to test specific stimuli.…”

High toluene exposure risk increases risk of olfactory dysfunction in furniture workers

“…Potential hazard level: the score for toluene exposure had been predetermined from hazard rating tables, giving a score of 3. (14) Exposure level: the score was calculated by comparing the mean weekly exposure level (E) with the permissible exposure limit (PEL) for toluene of 50 ppm or 18 mg/m 3 . (18) The value for E was obtained by multiplying duration of exposure (D) with the exposure frequency (F), and the measured toluene level (M) and dividing the product by total working hours per week (W).…”

“…The olfactory threshold value was estimated as the mean of the last 4 staircase reversal points, with scores of 1 to 16. (14,16) Determination of odor discrimination (D) was performed using 3 pens, with 2 pens containing the same odorant and 1 pen containing a different odorant. The testing used the technique of 3-alternative forced-choice, in which the subject had to identify the one pen that had a different odor.…”

“…The total score ranged from 0 to 16 for a set of 16 pens containing odorants. (14,16) In the testing for odor threshold and odor discrimination, the subject was blindfolded to prevent visual identification of the pens. (15) The odor identification (I) test used 16 odorants with the multiple forced-choice design method.…”