Characterization of the Sniff magnitude test

Objective: To evaluate the potential utility of the Sniff Magnitude Test (SMT) as a clinical measure of olfactory function. Design: Between-subject designs were used to compare the SMT and University of Pennsylvania Smell Identification Test (UPSIT) in study participants from a broad range of ages. Subjects: A total of 361 individuals from retirement communities and an urban university and patients from an otolaryngology clinic. Intervention: Study participants completed the SMT and UPSIT using standard procedures. Main Outcome Measures: The UPSIT was scored using standard procedures to calculate the number of correctly identified odors; a score that can range from 0 to 40 correct. The measure of olfactory function generated by the SMT is the "sniff magnitude ratio," defined as the mean sniff magnitude generated by the odor stimuli divided by the mean sniff magnitude to nonodorized air blanks. Results: The SMT generally showed good agreement with UPSIT diagnostic categories, although SMT scores were only modestly elevated in the mild and modest hyposmia range of the UPSIT. Age-related decline in olfactory ability was evident on the UPSIT at younger ages than that seen with the SMT. As predicted, otolaryngology patients with olfactory complaints were found to be impaired on both the UPSIT and SMT. Conclusions: The SMT provides a novel method for evaluating the sense of smell that shows good general agreement with the UPSIT. Its minimal dependence on language and cognitive abilities provides some advantages over odor identification tests. There is some indication that the UPSIT may be more sensitive to olfactory (and/or nonolfactory) deficits. We conclude that sniffing behavior can be exploited for the clinical evaluation of olfaction. A comparison of performance on odor identification and sniffing tests may provide novel insight into the nature of olfactory problems in a variety of patient populations.