Psychophysical Tests

Despite the fact that a wide range of psychophysical olfactory tests are available for accurately assessing olfactory function, most are of unknown reliability and validity, cumbersome, and suffer for lack of normative data. Fortunately, during the last few years a handful of standardized and practical psychophysical tests have been developed, including several brief self-administered screening tests (e. g., 59,60,61 and 62). The most widely used of these tests is the UPSIT, known commercially as the Smell Identification Test (Sensonics, Inc., Haddonfield, NJ) (59,60) (Fig. 22.3). This test, which is available in English, Spanish, French, and German language versions, has been administered to nearly 200,000 patients since its invention in the early 1980s. The UPSIT can be self-administered in 10 to 15 minutes by most patients in the waiting room and scored in less than a minute by nonmedical personnel. This test consists of four booklets containing 10 odorants apiece. The stimuli are embedded in 10- to 50-pm diameter microencapsulated crystals located on "scratch and sniff” strips on the bottom of the pages of the test booklets. Above each strip is a multiple choice question with four response alternatives. The patient is required to choose an answer, even if none seems appropriate or no odor is perceived (i. e., the test is forced choice). This encourages the patient to carefully sample all of the stimuli and provides a means for detecting malingering; because chance performance is 10 of 40, very low scores reflect avoidance, and hence recognition, of the correct answer. Norms based on the administration of this test to nearly 4,000 people are provided and an individual's percentile rank established relative to persons of the same age and gender. This test also makes it possible to classify an individual's function, on an absolute basis, into one of six categories: normosmia, mild microsmia, moderate microsmia, severe microsmia, anosmia, and probable malingering. The reliability of this test is very high (test-retest Pearson r = 0.94).

FIGURE 22.3. University of Pennsylvania Smell Identification Test (UPSIT; commercially known as the Smell Identification Test™ or SIT, Sensonics, Inc., Haddon Heights, NJ). This 40-item microencapsulated odor ("scratch and sniff”) test consists of four test booklets, each containing 10 odorants with four-alternative response answers to each. Norms for this test are based on nearly 4,000 subjects spanning the entire age range. (Photo courtesy of Sensonics, Inc., Haddon Heights, NJ.)

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