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Equating scores of the University of Pennsylvania smell identification test and sniffin' sticks test in patients with Parkinson's disease

Lawton, Michael, Hu, Michele T.M., Baig, Fahd, Ruffmann, Claudio, Barron, Eilidh, Swallow, Diane M.A., Malek, Naveed, Grosset, Katherine A., Bajaj, Nin, Barker, Roger A., Williams, Nigel Melville ORCID:, Burn, David J., Foltynie, Thomas, Morris, Huw R., Wood, Nicholas W., May, Margaret T., Grosset, Donald G. and Ben-Shlomo, Yoav 2016. Equating scores of the University of Pennsylvania smell identification test and sniffin' sticks test in patients with Parkinson's disease. Parkinsonism & Related Disorders 33 , pp. 96-101. 10.1016/j.parkreldis.2016.09.023

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Background Impaired olfaction is an important feature in Parkinson's disease (PD) and other neurological diseases. A variety of smell identification tests exist such as “Sniffin’ Sticks” and the University of Pennsylvania Smell Identification Test (UPSIT). An important part of research is being able to replicate findings or combining studies in a meta-analysis. This is difficult if olfaction has been measured using different metrics. We present conversion methods between the: UPSIT, Sniffin’ 16, and Brief-SIT (B-SIT); and Sniffin’ 12 and Sniffin’ 16 odour identification tests. Methods We used two incident cohorts of patients with PD who were tested with either the Sniffin’ 16 (n = 1131) or UPSIT (n = 980) and a validation dataset of 128 individuals who took both tests. We used the equipercentile and Item Response Theory (IRT) methods to equate the olfaction scales. Results The equipercentile conversion suggested some bias between UPSIT and Sniffin’ 16 tests across the two groups. The IRT method shows very good characteristics between the true and converted Sniffin’ 16 (delta mean = 0.14, median = 0) based on UPSIT. The equipercentile conversion between the Sniffin’ 12 and 16 item worked well (delta mean = 0.01, median = 0). The UPSIT to B-SIT conversion showed evidence of bias but amongst PD cases worked well (mean delta = −0.08, median = 0). Conclusion We have demonstrated that one can convert UPSIT to B-SIT or Sniffin’ 16, and Sniffin’ 12 to 16 scores in a valid way. This can facilitate direct comparison between tests aiding future collaborative analyses and evidence synthesis.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Medicine
MRC Centre for Neuropsychiatric Genetics and Genomics (CNGG)
Neuroscience and Mental Health Research Institute (NMHRI)
Subjects: R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Uncontrolled Keywords: Olfaction; Sniffin’ Sticks; University of Pennsylvania Smell Identification Test; Equating; Item Response Theory
Publisher: Elsevier
ISSN: 1353-8020
Date of First Compliant Deposit: 10 November 2016
Date of Acceptance: 23 September 2016
Last Modified: 05 May 2023 05:53

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