With recent changes in Korea from the ancient agricultural life to an urban culture, the effect on quality of life of smell is also changing. Olfaction as an important function for sensing the world can be reduced by problems such as infection, trauma, or neurodegenerative diseases. Therefore, tests that can accurately assess olfactory function are needed [1]. Olfactory function can be assessed through examination such as olfactory threshold, olfactory discrimination, and olfactory identification test [2]. Of these, olfactory identification test has advantages in that the test is easy for both examiner and subjects, can be performed in a relatively short time, and can be useful in early diagnosis of illnesses such as Alzheimer's disease or Parkinson's disease [3,4]. To improve the accuracy of the identification test, each culture should develop the test to match the environment of their culture.

T & T olfactometer test, developed in Japan, has odor items that are easily recognizable to many people [5], and University of Pennsylvania smell identification test (UPSIT) has items that are easily recognizable to people of various groups in the United States [6]. The supplemental cross-cultural smell identification test (CC-SIT) was introduced that chose the 12 odor items that show a high detection rate in a different culture [7]. Sniffin' stick test, developed by Kobal [8], chose items that are familiar to Germans, and is used for olfactory assessment in many countries of Europe. Scandinavian odor-identification test (SOIT) was developed with familiar items for Scandinavian cultures independently, although they share the European cultural area [9]. In Korea, we developed Korean version of Sniffin' sticks (KVSS) to evaluate olfactory function by modifying the Sniffin' Stick test with odors familiar to Koreans [10]. Recently developed odor stick identification test for Japanese (OSIT-J) asks not only for the correct answer but for the distracters on the basis of familiarity [11]. To compare with other culture areas, the choice of the distracters is important as well as the correct answers.

Thus the items of olfactory identification test should be as familiar as possible to the subjects. CCSIT, widely used in Korea, did not include Koreans during its development. The identification test of KVSS, created by using odors familiar to Koreans, contained unfamiliar items such as lime, coconut, and blackberry, making it difficult to assure the accuracy of the test.

Accordingly, the authors modified distracters based upon research about familiar olfactory impressions for Koreans, and then compared the results of the identification test with the previously used one.

Choosing odorants for an olfactory test has several limitations when used in different nations or cultural areas [12]. In this study, we compared the results of olfactory identification test by changing not only the items but the distracters into those which are familiar to subjects.

After changing the distracters, the identification rates of licorice, apple, and rosin increased from 16%, 28%, 51% to 36%, 66%, 70%, respectively. This shows the same results as Shu's, who noted that his identification rate increased from 52%, 62% to 79%, 100%, respectively by substituting familiar items for leather, cinnamon, and licorice [13] (Table 1). Nordin developed a test suitable for people of Scandinavian, SOIT, which had commonly used odor items and the examples through the Confusion matrix [9]. By comparing the Japanese and American OSIT-J, there is an obvious contrast in the familiarity of odorants and there was also a significant difference in analysis of distracters. Therefore in order to increase the accuracy of the olfactory test, replacement of the less familiar distracters is necessary. In comparison with Japanese and American with OSIT-J, different familiarity to the odor items and the analysis of distracters were noted. Hence the accuracy of the olfactory test can be increased by replacing the distracters which have low familiarity [13]. We investigated odorants familiar to Koreans and those having low differences of recognition between ages or occupation, and raised the accuracy by adding them to KVSS-II odor items. On the other hand, the similarity of the correct answer is also an important factor for influencing the correct answer rate. But we focused on familarity of distracters in this study. So we discarded the distracters which had extremely low or high similarity with the odorant for increasing familiarity of distracters.

With increasing age, olfactory function tends to decrease even with more familiar distracters, compared with subjects in their 20s to 40s. The older subjects' scores of olfactory identification test were statistically significantly different from the younger age groups (P<0.05) (Table 2, Fig. 2). The modified KVSS II identification test well reflected the effect of age on olfactory function, a result similar to the original version of KVSS II identification test.

The scores of the original version of olfactory test which has distracters with lower familiarity underestimated olfactory function. The correlation of the relationship between subjective olfactory function and the score of olfactory function test was improved by replacing the distracters (Figs. 3, 4). In the case of CCSIT which was made for UPSIT multiculturalism, there are some items of low familiarity even though Japanese people participated in the development of the test, since the scores were not very high for middle aged subjects with normal olfactory identification test [14], a result similar to the authors' findings.

The items on olfactory identification tests undergo various influences by their cultures and changing the distracters by familiarity lead to a more valid test. Thus the identification olfactory test in KVSS-II which is used widely in Korea would be more accurate by changing to more familiar items to Koreans.

In conclusions, we suggest that the olfactory function will give more precise results if some items replace others more familiar to people to raise the accuracy of the olfactory identification test, and with this, we can improve our own test.