Assessment of the Sniff Magnitude Test as a clinical test of olfactory function

Olfactory threshold and odor identification tasks currently serve as the standard approaches to the clinical assessment of olfactory function. Although these methods can be used effectively with the average patient, they suffer from some limitations when used to evaluate children, people with cognitive impairment, or people from diverse cultural backgrounds. A novel approach to the clinical evaluation of olfactory function, the Sniff Magnitude Test, attempts to minimize the cognitive demands of an olfactory test and thereby overcome some of the limitations of alternative tests. This is achieved by measuring the reflex-like reduction in sniffing that occurs when a malodor is encountered. The reliability and the validity of the Sniff Magnitude Test were assessed by testing people on two occasions using the University of Pennsylvania Smell Identification Test (UPSIT), a butanol threshold task, the Alcohol Sniff Test, and the Sniff Magnitude Test. The test-retest reliability of the Sniff Magnitude Test was r=.80, higher than the butanol thresholds and Alcohol Sniff Test but somewhat lower than the UPSIT. Performance on the Sniff Magnitude Test (the sniff magnitude to a malodor relative to nonodorized air) was correlated between r=-.61 and r=-.66 with the other measures of olfactory function. This range of correlations was comparable to that observed between the butanol threshold, the UPSIT, and the Alcohol Sniff Test. Finally, evidence for the advantages of the Sniff Magnitude Test, as compared to the UPSIT, was provided by a study with young children. It is concluded that the Sniff Magnitude Test has significant potential as a clinical measure of olfactory function, and that further testing and development of this method are warranted.