Assessment of the influence of cognition and cognitive processing speed on three tests of olfaction.

The extent to which measures of working memory, cognitive speed, and verbal retrieval are associated with performance on tests of olfaction was evaluated in a sample of 138 older adults. Structural equation modeling techniques indicated that verbal retrieval difficulties significantly affect performance on the University of Pennsylvania Smell Identification Test (UPSIT). Further, poor working memory and slow cognitive speed significantly affect performance on the UPSIT and the phenyl ethyl alcohol threshold test. The Sniff Magnitude Test was not influenced by any of the cognitive variables. Odor threshold and identification tasks may overestimate olfactory loss when cognitive impairment is not taken into account.

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.

Neuronal chloride accumulation in olfactory epithelium of mice lacking NKCC1.

When stimulated with odorants, olfactory receptor neurons (ORNs) produce a depolarizing receptor current. In isolated ORNs, much of this current is caused by an efflux of Cl-. This implies that the neurons have one or more mechanisms for accumulating cytoplasmic Cl- at rest. Whether odors activate an efflux of Cl- in intact olfactory epithelium, where the ionic environment is poorly characterized, has not been previously determined. In mouse olfactory epithelium, we found that >80% of the summated electrical response to odors is blocked by niflumic acid or flufenamic acid, each of which inhibits Ca2+-activated Cl- channels in ORNs. This indicates that ORNs accumulate Cl- in situ. Recent evidence has shown that NKCC1, a Na+-K+-2Cl- cotransporter, contributes to Cl- accumulation in mammalian ORNs. However, we find that the epithelial response to odors is only reduced by 39% in mice carrying a null mutation in Nkcc1. As in the wild-type, most of the response is blocked by niflumic acid or flufenamic acid, indicating that the underlying current is carried by Cl-. We conclude that ORNs effectively accumulate Cl- in situ even in the absence of NKCC1. The Cl- -transport mechanism underlying this accumulation has not yet been identified.

A comparison of the sniff magnitude test and the University of Pennsylvania Smell Identification Test in children and nonnative English speakers.

The sniff magnitude test (SMT) is a reliable and rapid clinical test of olfactory function that is minimally dependent on cognitive and linguistic abilities. In this study, we compared performance on the SMT and University of Pennsylvania Smell Identification Test (UPSIT) in samples of children and nonnative English speakers. Previous research has shown that these populations perform poorly on the UPSIT as compared with young, healthy U.S. adults. Such performance differences may reflect variations in memory/cognition and language/culture rather than olfactory abilities. The UPSIT scores of children and of Indian and Chinese graduate students were found to be lower than those of young U.S. adults. By contrast, these groups did not perform more poorly than U.S. adults did on the SMT. The results are consistent with findings from our studies, with the elderly showing that performance on the UPSIT, but not the SMT, is significantly correlated with measures of memory, language and other cognitive abilities. The findings highlight the utility of the SMT when evaluating the olfactory ability of the very young, older adults and people with diverse linguistic and cultural backgrounds.

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.