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Characterization of the Sniff Magnitude Test ORIGINAL ARTICLE Characterization of the Sniff Magnitude Test Robert A. Frank, PhD; Robert C. Gesteland, PhD; Jason Bailie, BS; Konstantin Rybalsky, BS; Allen Seiden, MD; Mario F. Dulay, PhD Objective: To evaluate the potential utility of the Sniff Results: The SMT generally showed good agreement with Magnitude Test (SMT) as a clinical measure of olfactory UPSIT diagnostic categories, although SMT scores were function. only modestly elevated in the mild and modest hypo- smia range of the UPSIT. Age-related decline in olfac- Design: Between-subject designs were used to com- tory ability was evident on the UPSIT at younger ages than pare the SMT and University of Pennsylvania Smell Iden- that seen with the SMT. As predicted, otolaryngology pa- tification Test (UPSIT) in study participants from a broad tients with olfactory complaints were found to be im- range of ages. paired on both the UPSIT and SMT. Subjects: A total of 361 individuals from retirement com- Conclusions: The SMT provides a novel method for munities and an urban university and patients from an evaluating the sense of smell that shows good general otolaryngology clinic. agreement with the UPSIT. Its minimal dependence on language and cognitive abilities provides some advan- Intervention: Study participants completed the SMT and UPSIT using standard procedures. tages over odor identification tests. There is some indi- cation that the UPSIT may be more sensitive to olfac- Main Outcome Measures: The UPSIT was scored us- tory (and/or nonolfactory) deficits. We conclude that ing standard procedures to calculate the number of cor- sniffing behavior can be exploited for the clinical evalu- rectly identified odors; a score that can range from 0 to ation of olfaction. A comparison of performance on odor 40 correct. The measure of olfactory function generated identification and sniffing tests may provide novel in- by the SMT is the “sniff magnitude ratio,” defined as sight into the nature of olfactory problems in a variety the mean sniff magnitude generated by the odor stimuli of patient populations. divided by the mean sniff magnitude to nonodorized air blanks. Arch Otolaryngol Head Neck Surg. 2006;132:532-536 T IS ESTIMATED THAT SOME FORM available,1 so accurate assessment is of olfactory disorder afflicts at needed. least 1% of the general adult The most common clinical methods of population and 50% or more of olfactory evaluation are based on odor de- people older than 65 years.1 Ol- tection and identification.8-11 These meth- Ifactory disorders can be traced to a di- ods have been used productively to char- verse set of causes that include upper res- acterize olfactory disorders in a variety of piratory tract infections, nasal and sinus patient populations, but they have some disease, developmental disorders, endo- drawbacks. Odor detection thresholds are crine problems, head trauma, and neuro- only moderately reliable, are time consum- psychiatric diseases.1-3 Anosmia (loss of the ing, involve complex series of odor presen- sense of smell) and hyposmia (a dimin- tation, and demand focused attention to an ished sense of smell) have been noted as ephemeral stimulus. Odor identification Author Affiliations: early symptoms of Alzheimer disease and tests require patients to sniff odorant CompuSniff, LLC (Drs Frank idiopathic Parkinson disease.4,5 These facts samples and then identify or label them. The and Gesteland), and support the routine testing of olfactory interpretation of these tests can become Departments of Psychology abilities in older adults, especially in light problematic when evaluating children, (Drs Frank and Dulay and of the finding that people are poor judges people with impaired cognitive function, Messrs Bailie and Rybalsky), 6,7 Cell Biology (Dr Gesteland), of their own olfactory abilities. In addi- and individuals from diverse cultural and 12-14 and Otolaryngology tion, effective treatments for conductive linguistic backgrounds. (Dr Seiden), University of olfactory loss (ie, loss associated with poor The Sniff Magnitude Test (SMT) (Com- Cincinnati, Cincinnati, Ohio. airflow to the olfactory epithelium) are puSniff, LLC, Cincinnati, Ohio) was de- (REPRINTED) ARCH OTOLARYNGOL HEAD NECK SURG/ VOL 132, MAY 2006 WWW.ARCHOTO.COM 532 ©2006 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/25/2021 veloped to complement odor detection and identifica- tion tests by overcoming some of the limitations of the High Sniff to Air Only more traditional tests. The SMT is based on a well- Sniff to Odor established reduction in sniff magnitude that normally occurs in response to an odor. A number of studies have demonstrated that sniff vigor and duration play an im- portant role in modulating odor perception.15,16 Laing17 reported that sniff volume is reduced as odorant concen- Sniff Pressure tration increases, an observation subsequently verified by Low investigators from several laboratories.18-21 Given the simple, rapid nature of the sniff response, it may be buffered from 0 variations in age, language, culture, and cognitive ability. 0 1.0 2.0 If odorant-induced modulation of sniffing can be used as Time, s a measure of the early events in olfactory processing, its combination with tests that rely on cognitive abilities (eg, Figure 1. Depiction of hypothetical sniff pressure measurements to odor identification tests) may provide a powerful ap- nonodorized air (solid line) and an odor stimulus (dotted line). Note that proach to differentiating between olfactory deficits caused sniffs produce negative pressure so that high pressure refers to high by loss of primary sensory input into the olfactory system negative pressure. and dysfunction of higher-order processing associated with troposmia, phantosmia, or olfactory agnosia. OLFACTORY TESTS The SMT is based on the reduction in sniffing that nor- mally occurs when an odor is encountered. Sniffs to University of Pennsylvania Smell Identification Test stimuli composed of nothing but nonodorized air are longer and more vigorous compared with sniffs to odor- The UPSIT10 is the most widely used olfactory test in the world, ized air, and this difference can be used as an indicator having been administered to nearly 100 000 persons in the last of smell function (Figure 1). When a patient’s sense of decade. In this test, the patient is required to identify, in a 4-al- smell is impaired, this normal, odor-induced decrease in ternative multiple-choice format, each of 40 odorants pre- sniffing is reduced or eliminated. sented on microencapsulated “scratch and sniff” labels. The de- Initial studies demonstrated the feasibility of the SMT pendent measure is the number of items correctly answered. and some of its advantages. For example, it was shown The UPSIT was completed in the presence of a research assis- that the odor-induced sniff suppression is not affected tant who answered questions and offered help as requested. The by deficits in memory or attention in older adults and UPSIT was scored using standard procedures to calculate the that the SMT scores of children (who do poorly on odor number of correctly identified odors, this being a score that can identification tests) did not differ from those of adults.14,22,23 range from 0 to 40 correct. The present investigation had 2 main goals. One was to Sniff Magnitude Test more fully characterize the SMT in a sample of people that was diverse by age and olfactory abilities. The Uni- The SMT was administered as described previously.14 The SMT versity of Pennsylvania Smell Identification Test (UPSIT) device and a photograph of a person prepared to sniff are shown also was administered to allow for a comparison with the in Figure 2. The odor canisters contain either no odor (ie, they SMT. Good general agreement between the SMT and serve as nonodorized air blanks) or they contain 5.0 mL of an UPSIT was expected for the adults tested in this study. odor stimulus diluted in mineral oil. During testing, the par- The second goal was to demonstrate that a sample of pa- ticipant wears a bilateral nasal cannula of the type used to pro- tients with olfactory complaints would produce abnor- vide oxygen to patients with limited respiratory capacity (as mal results on the SMT. shown in Figure 2). A participant’s sniff creates a negative pres- sure that is sensed by a pressure transducer connected to the cannula and an analog-to-digital processing board located within METHOD a controller device. The digitized output signal of the board is sent to a laptop computer. Within milliseconds of detecting a SUBJECTS sniff, the computer opens the lid of the testing canister, thereby exposing the participant to any odor stimulus within the can- A sample of 361 individuals with a range of olfactory abilities ister. This all occurs very rapidly (within 15 milliseconds) once was recruited. Recruitment sites included local retirement com- a sufficient sniff pressure is achieved, and sniff pressure mea- munities, students and employees at the University of Cincin- surements are recorded by the computer every 10 millisec- nati (Cincinnati, Ohio), and patients from an otolaryngology onds until the transducer detects a return to ambient air pres- clinic in Cincinnati. Participants were recruited through ad- sure. Thus, data from a single sniff are recorded on each trial. vertisements in local newspapers and bulletin boards and Four stimulus canisters were used in the present study: 1 through physician referrals. The ears, nose, and throat (ENT) was a no-odor stimulus (air blank); 1 contained 5.0 mL of a patients included individuals with specific olfactory com- mixture composed of 1.0 mL of liquid methylthiobutyrate (MTB, plaints as well as other patients with problems such as chronic also known as S-methylthiobutanoate, 98% purity) in 99 mL sinusitis, rhinitis, nasal polyps, and other conditions rou- of mineral oil (1.0% vol/vol); 1 contained 5.0 mL of a mixture tinely encountered by an ENT physician.
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