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Olfactory thresholds of the U.S. Population of home-dwelling older adults: development and validation of a short, reliable measure.

Kern DW, Schumm LP, Wroblewski KE, Pinto JM, Hummel T, McClintock MK - PLoS ONE (2015)

Bottom Line: Simulated subjects were assigned n-butanol thresholds drawn from the estimated normosmic distribution and based on these and the model, we simulated administration of both the staircase and constant stimuli methods.Our results replicate both the correlation between the two methods and their reliability as previously reported by studies using human subjects.Thus, testing with a fast, 6-item constant stimuli protocol is informative, and permits olfactory testing in previously inaccessible research settings.

View Article: PubMed Central - PubMed

Affiliation: Institute for Mind and Biology and Department of Comparative Human Development, The University of Chicago, Chicago, IL, United States of America.

ABSTRACT
Current methods of olfactory sensitivity testing are logistically challenging and therefore infeasible for use in in-home surveys and other field settings. We developed a fast, easy and reliable method of assessing olfactory thresholds, and used it in the first study of olfactory sensitivity in a nationally representative sample of U.S. home-dwelling older adults. We validated our method via computer simulation together with a model estimated from 590 normosmics. Simulated subjects were assigned n-butanol thresholds drawn from the estimated normosmic distribution and based on these and the model, we simulated administration of both the staircase and constant stimuli methods. Our results replicate both the correlation between the two methods and their reliability as previously reported by studies using human subjects. Further simulations evaluated the reliability of different constant stimuli protocols, varying both the range of dilutions and number of stimuli (6-16). Six appropriately chosen dilutions were sufficient for good reliability (0.67) in normosmic subjects. Finally, we applied our method to design a 5-minute, in-home assessment of older adults (National Social Life, Health and Aging Project, or NSHAP), which had comparable reliability (0.56), despite many subjects having estimated thresholds above the strongest dilution. Thus, testing with a fast, 6-item constant stimuli protocol is informative, and permits olfactory testing in previously inaccessible research settings.

No MeSH data available.


Histogram and Bland-Altman plot.A. Histogram of 590 normosmic staircase-estimated thresholds (as determined by the mean of the last 4 reversals), together with a normal density curve with the same mean and standard deviation (solid black). In addition, the distribution of estimated thresholds from the fitted model is also plotted (dashed grey).B. Corresponding Bland-Altman plot comparing staircase-estimated thresholds and model-estimated thresholds among the 590 normosmics together with a LOWESS smoother.
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pone.0118589.g001: Histogram and Bland-Altman plot.A. Histogram of 590 normosmic staircase-estimated thresholds (as determined by the mean of the last 4 reversals), together with a normal density curve with the same mean and standard deviation (solid black). In addition, the distribution of estimated thresholds from the fitted model is also plotted (dashed grey).B. Corresponding Bland-Altman plot comparing staircase-estimated thresholds and model-estimated thresholds among the 590 normosmics together with a LOWESS smoother.

Mentions: Among the normosmic sample, the estimated slope parameter (β) was 1.12 (SE = 0.06), and the mean and variance of the αi were estimated as 10.5 (SE = 0.55) and 16.6 (SE = 2.0), respectively. Fig. 1A shows a histogram of the 590 staircase-estimated thresholds determined from the average of the last four reversals, together with a Normal density curve with the same mean and standard deviation (solid black). In addition, the distribution of thresholds (obtained by dividing αi by β̂) estimated from the IRT model is also plotted (grey dashed). The means of the two distributions are nearly identical, demonstrating excellent correspondence between the model-estimated thresholds and threshold estimates obtained using the staircase method, thereby validating the model. As expected, the variance of the model-estimated distribution is slightly greater, because the staircase method does not permit threshold estimates outside of the range of dilutions administered (1–16).


Olfactory thresholds of the U.S. Population of home-dwelling older adults: development and validation of a short, reliable measure.

Kern DW, Schumm LP, Wroblewski KE, Pinto JM, Hummel T, McClintock MK - PLoS ONE (2015)

Histogram and Bland-Altman plot.A. Histogram of 590 normosmic staircase-estimated thresholds (as determined by the mean of the last 4 reversals), together with a normal density curve with the same mean and standard deviation (solid black). In addition, the distribution of estimated thresholds from the fitted model is also plotted (dashed grey).B. Corresponding Bland-Altman plot comparing staircase-estimated thresholds and model-estimated thresholds among the 590 normosmics together with a LOWESS smoother.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4359123&req=5

pone.0118589.g001: Histogram and Bland-Altman plot.A. Histogram of 590 normosmic staircase-estimated thresholds (as determined by the mean of the last 4 reversals), together with a normal density curve with the same mean and standard deviation (solid black). In addition, the distribution of estimated thresholds from the fitted model is also plotted (dashed grey).B. Corresponding Bland-Altman plot comparing staircase-estimated thresholds and model-estimated thresholds among the 590 normosmics together with a LOWESS smoother.
Mentions: Among the normosmic sample, the estimated slope parameter (β) was 1.12 (SE = 0.06), and the mean and variance of the αi were estimated as 10.5 (SE = 0.55) and 16.6 (SE = 2.0), respectively. Fig. 1A shows a histogram of the 590 staircase-estimated thresholds determined from the average of the last four reversals, together with a Normal density curve with the same mean and standard deviation (solid black). In addition, the distribution of thresholds (obtained by dividing αi by β̂) estimated from the IRT model is also plotted (grey dashed). The means of the two distributions are nearly identical, demonstrating excellent correspondence between the model-estimated thresholds and threshold estimates obtained using the staircase method, thereby validating the model. As expected, the variance of the model-estimated distribution is slightly greater, because the staircase method does not permit threshold estimates outside of the range of dilutions administered (1–16).

Bottom Line: Simulated subjects were assigned n-butanol thresholds drawn from the estimated normosmic distribution and based on these and the model, we simulated administration of both the staircase and constant stimuli methods.Our results replicate both the correlation between the two methods and their reliability as previously reported by studies using human subjects.Thus, testing with a fast, 6-item constant stimuli protocol is informative, and permits olfactory testing in previously inaccessible research settings.

View Article: PubMed Central - PubMed

Affiliation: Institute for Mind and Biology and Department of Comparative Human Development, The University of Chicago, Chicago, IL, United States of America.

ABSTRACT
Current methods of olfactory sensitivity testing are logistically challenging and therefore infeasible for use in in-home surveys and other field settings. We developed a fast, easy and reliable method of assessing olfactory thresholds, and used it in the first study of olfactory sensitivity in a nationally representative sample of U.S. home-dwelling older adults. We validated our method via computer simulation together with a model estimated from 590 normosmics. Simulated subjects were assigned n-butanol thresholds drawn from the estimated normosmic distribution and based on these and the model, we simulated administration of both the staircase and constant stimuli methods. Our results replicate both the correlation between the two methods and their reliability as previously reported by studies using human subjects. Further simulations evaluated the reliability of different constant stimuli protocols, varying both the range of dilutions and number of stimuli (6-16). Six appropriately chosen dilutions were sufficient for good reliability (0.67) in normosmic subjects. Finally, we applied our method to design a 5-minute, in-home assessment of older adults (National Social Life, Health and Aging Project, or NSHAP), which had comparable reliability (0.56), despite many subjects having estimated thresholds above the strongest dilution. Thus, testing with a fast, 6-item constant stimuli protocol is informative, and permits olfactory testing in previously inaccessible research settings.

No MeSH data available.