A threshold-like measure for the assessment of olfactory sensitivity: the "random" procedure

Many tests of olfactory dysfunction are either too complex, too expensive, or too time-consuming to be of use in routine clinical testing. Thus, the p resent multicenter study was undertaken to investigate a new approach, the so-called "random" test. In this test different concentrations of citronell al and phenyl ethyl alcohol are applied according to a pre-established orde r; patients are asked to identify the odor if possible. The test score is t he sum of correctly identified odors. Test administration takes about 10 mi n. Two studies were performed. Basic characteristics of the test were explo red in experiment 1 in 176 healthy subjects (76 male, 100 female; age 12-85 years, mean age 30 years), namely test-retest reliability, correlation wit h other measures of olfactory sensitivity, and sensitivity of the test to d ifferences in age and gender. In the second experiment the test was tried i n 97 patients (45 male, 52 female; age 19-78 years, mean age 47 years) in a clinical environment to investigate its usefulness in diagnosing olfactory loss. The "random"-test was found (1) to exhibit a test-retest reliability similar to that reported for established measures of olfactory function (r = 0.71; P < 0.001), (2) to correlate with other measures of olfactory sens itivity (0.82 > r > 0.60; P < 0.001), (3) to differentiate between expected differences in olfactory sensitivity in relation to gender (t > 2.602, P < 0.011), and (4) to discriminate between different degrees of olfactory los s (F > 36.6, P < 0.001). Based on these data, and the fact that the new tes t requires little time and is easy to use, this approach can be expected to suit clinical needs.