Chemical Senses Vol. 29 No. 7 © Oxford University Press
2004; all rights reserved
Usefulness of the Odor Stick Identification Test for Japanese Patients with Olfactory Dysfunction
1 Department of Otorhinolaryngology, Hyogo College of Medicine, Nishinomiya City, Hyogo 663-8501, Japan, 2 Department of Otorhinolaryngology, Meiwa Hospital, 4-31 Agenaruo-cho, Nishinomiya-city, Hyogo 663-8186, Japan, 3 Department of Otorhinolaryngology, Hyogo Prefectural Kaibara Hospital, 1-5208 Kaibara, Kaibara-cho, Hikami-gunn, Hyogo 669-3395, Japan, 4 National Institute of Advanced Industrial Science and Technology, Neuroscience Research Institute, Central 6, 1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan and 5 Takasago International Corporation, Japan, Nissei Aroma Square 17F, 5-37-1 Kamata, Ota-ku, Tokyo 144-8721, Japan
Correspondence to be sent to: Yoshiteru Hashimoto, Department of Otolaryngology, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya City, Hyogo 663-8501, Japan. e-mail: y-h-1975{at}hyo-med.ac.jp
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Abstract |
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The odor stick identification test (OSIT) is a new test of olfactory function recently developed for Japanese people. The purpose of the present study was to evaluate this test in relation to T&T olfactometry and the cross-cultural smell identification test (CC-SIT) by applying to 110 Japanese patients with olfactory disturbance. The averaged recognition thresholds for five odorants in T&T olfactometry, the number of correct answers in the CC-SIT and the rates of identification of 13 odorants in the OSIT were compared. The visual analogue scale (VAS) was also used to evaluate symptoms. The rate of identification of OSIT showed high and significant correlation coefficients with the averaged recognition thresholds of T&T olfactometry (–0.766, P < 0.001), with the number of correct answers in CC-SIT (0.754, P < 0.001) and with the VAS score (0.591, P < 0.001). In addition, on the identification performance measured by OSIT, we found significant differences between all pairs of four degrees of olfactory dysfunction except for one pair. Thus, we conclude that OSIT is useful for evaluating olfactory dysfunction in Japanese people.
Key words: cross-cultural smell identification test, odor stick identification test, olfactory disturbance, T&, T olfactometry, visual analogue scale
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Introduction |
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T&T olfactometry (Zusho, 1983
)
is the standard test used for measuring olfactory dysfunction in Japan. This test enables
the measurement of olfactory detection and recognition thresholds and is the only method
currently covered by Japanese health insurance (Miwa et al., 2001;
Fujii et al., 2002a,b).
Unfortunately, this test kit has not been well accepted for medical use because it
requires a special large-scale deodorant device to avoid strong odor pollution and,
moreover, measurement is a time-consuming process. Several other procedures have been
presented and used worldwide to evaluate olfactory ability. The University of
Pennsylvania smell identification test (UPSIT;
Doty et al., 1984) and the
cross-cultural smell identification test (CC-SIT;
Doty et al., 1996) have been
introduced as smell identification tests in the United States and the
‘Sniffin’ sticks’ test has been used in Germany (Kobal et al., 1996). However, some odors included
in these tests are unfamiliar to the Japanese and consequently the olfactory ability of
Japanese subjects may not be measured correctly by these tests.
The odor stick identification test (OSIT) is a new type of smell identification test
recently developed for the Japanese and can present 13 odors, all of which are familiar
to the Japanese (Saito et al.,
2001, 2003). A significant correlation coefficient between the average
recognition thresholds for T&T olfactometry and the rate of identification with OSIT
has been reported in Japanese subjects with normal olfaction (Saito et al., 2001). However, the
clinical application of OSIT to patients with olfactory dysfunction has not yet been
described. The purpose of the present study was to clarify the clinical utility of the
OSIT for Japanese patients with olfactory dysfunction.
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Materials and methods |
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This study was performed on 110 consecutive patients with olfactory dysfunction at the Department of Otolaryngology, Hyogo College of Medicine, from March 2001 to June 2002. The patients consisted of 44 men and 66 women with a mean age of 58.6 years. The patients were examined with the OSIT, T&T olfactometry and CC-SIT. Symptoms of olfactory disturbance were evaluated with the visual analogue scale (VAS; McCormack et al., 1988
). The
causative diseases were chronic sinusitis in 38 cases, upper respiratory infection in 31
cases, nasal allergy in 10 cases, rhinitis with inflammation of the olfactory cleft in
six cases, head trauma in four cases, acute sinusitis in one case, subarachnoid
hemorrhage in one case and unknown etiology in 19 cases. Odor Stick Identification Test (OSIT)
This test includes 13 odorants: perfume, rose, milk, Japanese orange, curry, roasted garlic, putrid smell, fermented beans/sweat socks, gas for cooker, menthol, Indian ink, wood and Japanese cypress (hinoki). These odors were chosen from odors familiar to the Japanese. The odorant for each odor was selected from pure chemicals, essential oils, or mixed odorants produced by the Takasago International Corporation. These odorants were packed in microcapsules, which were mixed in paste. Each paste was hardened in the form of a lipstick, which was called the ‘odor stick’ (Figure 1). Each odor stick was painted in a 2 cm circle on a thin paraffin paper by the examiner. The examiner folded this paper in half and rubbed it to grind the microcapsules and then passed it to a patient. The patient next opened and sniffed the paper. The patient was then given six alternatives: four odor names, including one correct name in principle, ‘not detected’ and ‘unknown’; the odorant of fermented beans/sweat socks was an exception. First, we asked patients to choose a correct one out of the four odor names. We suggested that patients select ‘unknown’ or ‘not detected’, when it was difficult to select one from the four odor names. ‘Unknown’ indicates that the presented odorant was detected but not recognized. This procedure was repeated for each odorant. The original method proposed using an answer sheet showing the difference between four alternatives of odor names and the two other ones, ‘unknown’ and ‘not detected’, by drawing a broken line between four alternatives of odor names and others or by putting others in parentheses. In the present study, we did not draw a broken line, but explained the difference verbally.
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T&T olfactometry
T&T olfactometry is the standard Japanese olfactory test and is routinely
performed clinically (Zusho, 1983).
This test consists of five standard odors: (A) roses, (B) burning, (C) sweat, (D) fruits
and (E) vegetable chips. The concentration is prepared at eight degrees, except (B),
which is prepared at seven degrees (Zusho,
1983;
Fujii et al., 2002a,b). This
test measures the detection and recognition thresholds. It is possible to evaluate
subjects’ olfactory ability as the average score of five odorants. In this study,
the average recognition threshold was defined based on the result of T&T olfactometry
by the mean recognition thresholds for five odorants (Takagi, 1987).
Cross-cultural smell identification test (CC-SIT)
The cross-cultural smell identification test (CC-SIT) consists of twelve odorants,
based on items from the University of Pennsylvania smell identification test (UPSIT). The
12 items (odorants) were selected as multicultural odorants from the UPSIT. The
‘scratch-and-sniff’ technique employed was based on mechanical release of
micro-encapsulated odorants. Smell identification was based on a multiple choice test
from a list of four items (Doty et al.,
1996).
Visual analogue scale (VAS)
The visual analogue scale (VAS) has been used in psychological research since the
early twentieth century (Hayes and Patterson,
1921;
Freyd, 1923). In the present study, we
used VAS to measure the symptoms of olfactory dysfunction. VAS consists of a 10 cm line,
both ends of which have statements of the maximal and minimal extremes (McCormack et al., 1988). The subjects
were asked to indicate their feelings by marking the line at the appropriate point
between the two extreme statements, defined as ‘anosmia’ and
‘normal’ in this study. The scales were scored by measuring the distance from
the minimal endpoint to the mark, on a predetermined measurement interval. The most
commonly chosen interval was in millimeters with a 10 cm line, producing a 100 point
scale (McCormack et al.,
1988).
Procedure
OSIT was performed by either of two of the eight authors. T&T and VAS were performed by a well-trained assistant. The OSIT and CC-SIT did not require a deodorant device and did not cause odor pollution. On the other hand, a deodorant device was required for T&T olfactometry. About 10 min were required to examine olfaction with OSIT, 12 min with the CC-SIT and 25 min with T&T olfactometry.
Data analysis
We calculated Pearson’s correlation coefficients between the each pair among the OSIT identification rate, the average recognition threshold by T&T olfactometry, CC-SIT score and VAS score. We also evaluated OSIT identification rate and CC-SIT score according to the degree of olfactory disturbance measured by T&T olfactometry, with one-way analysis of variance (ANOVA) and the post-hoc Tukey–Kramer test. In all cases, P-values below 0.05 were regarded as statistically significant.
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Results |
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Correlation among the results of OSIT, T&T olfactometry and CC-SIT
The correlations were –0.766 between the identification rate of OSIT and the average recognition threshold by T&T olfactometry (P < 0.001, n = 110; Figure 2A), –0.673 between CC-SIT score and the average recognition threshold by T&T olfactometry (P < 0.001, n = 90; Figure 2B) and 0.754 between the identification rate of OSIT and CC-SIT score (P < 0.001, n = 90; Figure 2C). These findings suggested that the three tests were all significantly correlated.
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Correlation between the results of VAS and each test
The correlations were 0.591 between the identification rate of OSIT and VAS score (P < 0.001, n = 110; Figure 3A), –0.479 between the average recognition threshold by T&T olfactometry and VAS score (P < 0.001, n = 110; Figure 3B) and 0.555 between CC-SIT score and VAS score (P < 0.001, n = 90; Figure 3C).
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The relations of OSIT to the degree of olfactory dysfunction
The degree of olfactory acuity was determined, for each participant, based upon the average recognition thresholds of five odorants assessed by T&T olfactometry. The average thresholds of 1.1–2.5 were defined as the ‘mild’ degree of olfactory dysfunction, 2.6–4.0 as ‘moderate’, 4.1–5.5 as ‘serious’ and 5.6–5.8 as ‘anosmia’. ANOVA revealed a significant difference of the identification performance among the degrees of olfactory dysfunction in both OSIT [F(3, 102) = 105, P < 0.01] and CC-SIT [F(3, 84) = 87, P < 0.01; Figure 4A,B]. A Tukey–Kramer’s post-hoc test revealed significant differences between all pairs of four degrees of olfactory dysfunction except for one pair (‘mild’ and ‘moderate’) in the identification performance of OSIT (Figure 4A); however, a Tukey–Kramer’s post-hoc test could not reveal significant differences between ‘mild’ and ‘moderate’ and between ‘moderate’ and ‘serious’ in the CC-SIT score (Figure 4B).
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The rate of correct identification of each odorant in OSIT
We calculated the rate of identification of each odorant in the ‘mild’ and ‘moderate’ groups of the degree of olfactory dysfunction in order to examine the validity of odorants. The mean rate of identification of 13 odorants was 60.5% and the rates of identification of two odorants, Japanese orange and gas for cooker, were <45.4% (mean rate – SD; Figure 5).
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The rate of selected answers for each odorant in OSIT in the ‘mild’ and ‘moderate’ groups
The rates of selected answers for each odorant in OSIT in the ‘mild’ and ‘moderate’ groups are shown in Figure 6. The rates of ‘unknown’ responses for the two odorants (Japanese orange and gas for cooker) were 23.3 ± 0% (average ± SEM) and the rates for the other odorants were 10.9 ± 1.89%. The two odorants, whose correct answer rates in OSIT were lower than ‘the mean rate – SD’ in the ‘mild’ and ‘moderate’ groups, showed a higher rate of ‘unknown’ responses than that for any one of the other odorants; however, we did not apply statistics because of the small sample size of one group.
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Discussion |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionConclusionAcknowledgementsReferences |
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The only test of olfaction currently recognized by Japanese national health insurance is T&T olfactometry. However, this test has not been widely used in Japan for three main reasons. First, T&T olfactometry requires large-scale ventilation equipment to avoid strong odor pollution. Secondly, this test usually presents only five odors, which is insufficient to evaluate odor identification ability. Lastly, this test takes a relatively long time (
30 min). OSIT, on the other hand, does not require the use of
a deodorant device, examines 13 kinds of odorants familiar to the Japanese in their daily
life and only requires 10 min to perform. Therefore, we consider OSIT to be a more
efficient test for examining olfactory ability in routine daily clinical practice. OSIT is a smell identification test, while T&T olfactometry measures smell recognition threshold and detection threshold simultaneously. However, the high and significant correlation was observed between the identification rate of OSIT and the average recognition threshold by T&T olfactometry and between the rate of identification by OSIT and the VAS score. These results support the notion that OSIT well reflects subjective severity of olfactory disturbance.
There were significant differences among the each rate of identification by OSIT in the degrees of olfactory disturbance defined by T&T olfactometry without the one pair ‘mild’ and ‘moderate’ (Figure 4). A sample size of ‘mild’ was smaller than that of the other degrees, therefore, one needs to consider the significant difference between the ‘mild’ and ‘moderate’ with the larger sample size of ‘mild’. On the other hand, there were no significant differences not only between the ‘mild’ and ‘moderate’, but also between the ‘moderate’ and ‘serious’ olfactory disturbances in the CC-SIT score (Figure 4). We attribute this discrepancy to differences in used odorants and alternatives to be answered. Familiar odorants for Japanese are used in OSIT. As the alternatives to be answered, CC-SIT is a forced multiple choice test from a list of four items, while OSIT includes the additional choices of ‘not detected’ and ‘unknown’. Thus, OSIT can probably estimate the olfactory dysfunction of a patient more accurately than CC-SIT and can be used not only as a screening test for olfactory dysfunction, but also to measure the degree of olfactory ability.
The rates of identification in OSIT were approximately in accordance with the degree
of olfactory acuity (Figure
4). However, two particular odorants,
‘Japanese orange’ and ‘gas for cooker’, the rates of
identification were lower and the rates of ‘unknown’ response were higher
than that of any of the other 11 odorants (Figures
5 and
6). This may suggest that patients
tend to choose the ‘unknown’ response when it is difficult to select the
correct name of odorant. The subjective intensity of each odorant in OSIT was fitted
approximately from moderate to strong intensity and the percent correct of identification
was >80% in normal subjects, but the identification rate of ‘Japanese
orange’ was the lowest (Saito et
al., 1998, 2003). Although the 13 odorants in OSIT were familiar to the
Japanese, we think it was still difficult for patients with olfactory dysfunction to
identify these two odorants. In the case of ‘gas for cooker’, however, we
need to consider also the tendency of its odor to fade away immediately when the paraffin
paper is opened.
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Conclusion |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionConclusionAcknowledgementsReferences |
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OSIT was an easy, fast and compact olfactory test suitable for clinical use in screening for olfactory disturbance. OSIT could measure the degree of olfactory disturbance similar to T&T olfactometry. Patients with olfactory dysfunction may find it difficult to identify two odorants, ‘Japanese orange’ and ‘gas for cooker’. OSIT may be adapted for patients in other countries by choosing suitable, recognizable odors.
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Acknowledgements |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionConclusionAcknowledgementsReferences |
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The authors would like to express their sincere thanks to Ms Hosono for her help with T&T olfactometry.
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References |
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TopAbstractIntroductionMaterials and methodsResultsDiscussionConclusionAcknowledgementsReferences |
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Accepted June 11, 2004
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