Validity and Reliability of Persian Smell Identification Test

Smell Identification Tests (SIT) are routinely utilized for the clinical evaluation of olfactory function. Since Iran consists of various ethnic subgroups, the reliability and validity of this test as a national SIT are required to be evaluated across the country.   This cross-sectional study evaluated the cultural adaptation of SIT administered to 420 healthy volunteers from 6 various ethnic subgroups (i.e., Fars, Turk, Kurd, Lor, Baluch, and Arab) living in 7 cities (one city for each subgroup, and Tehran [capital of Iran] with mixed ethnicities). The SIT consists of pens pre-filled with 24 odorants. The correct identification response rate was evaluated in all and each subgroup. The test was performed twice on 60 participants with a 2-week interval to assess its reliability. The SIT was further administered to 150 cases with documented abnormal olfactory function to evaluate its validity.   The correct identification response rate was estimated at 70% for all odorants in all and each subgroup. The mean odor identification score was 21.41±1.37 (score range: 17- 24) with no significant difference among various subgroups. Moreover, the test-retest correlation coefficient was obtained at 0.77. The mean odor identification score in patients with olfactory impairment was 10.69±3.76, which was significantly different from that in healthy participants (P<0.001). The best cut-point for the beginning of olfactory impairment was 17.5 (95% CI: 9-100, Sensitivity=99, Specificity=81). Females obtained higher scores of odor identification, compared to males (P=0.025).   The results indicated the reliability and validity of the SIT, which can be used nationally for the assessment of olfactory function in various ethnic subgroups across the country.