A STUDY OF THE TEST-RETEST RELIABILITY OF 10 OLFACTORY TESTS

Ten tests of olfactory function (including tests of odor identificatio n, detection, discrimination, memory, and suprathreshold odor intensit y and pleasantness perception) were administered on two test occasions to 57 subjects ranging in age from 18 to 83 years. The stability of t he average test scores was determined across the two test sessions for 14 measures derived from these 10 tests and for subcomponents of the Japanese T&T olfactometer threshold test. In addition, the test-retest reliability (Pearson r) of each test measure was established. With th e exception of a response bias measure, the average test scores did no t differ significantly across the two test sessions. Statistically, th e reliability coefficients of the primary test measures fell into thre e general classes bound by the following r values: 0.43-0.53; 0.67-0.7 1; 0.76-0.90. Detection threshold values were more reliable than recog nition threshold values; those based upon a single ascending presentat ion series were much less reliable than those based upon a staircase p rocedure. The relationship between test length and reliability was exa mined for several of the tests and mathematically modeled. For example , within the staircase series incorporating the odorant phenyl ethyl a lcohol, reliability was related (R(2) = 0.984) to the number of revers als included in the threshold estimate by a function derived from the Spearman-Brown formula; namely, reliability = 0.455 # reversals/[1 0.455 (# reversals - 1)]. Reversal location, per se, had little influe nce on reliability. Overall, this study suggests that (i) considerable variation is present in the reliability of olfactory tests, (ii) reli ability is a function of test length, and (iii) caution is warranted i n comparing results from nominally different olfactory tests in applie d settings since the findings may, in some instances, simply reflect t he differential reliability of the tests.