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. 2013 Jul;21(7):607-22.
doi: 10.1016/j.jagp.2012.10.027. Epub 2013 Apr 18.

Subscale validation of the neuropsychiatric inventory questionnaire: comparison of Alzheimer's disease neuroimaging initiative and national Alzheimer's coordinating center cohorts

Paula T Trzepacz  1 , Andrew Saykin, Peng Yu, Phani Bhamditipati, Jia Sun, Ellen B Dennehy, Brian Willis, Jeffrey L Cummings; Alzheimer's Disease Neuroimaging Initiative
Affiliations

Subscale validation of the neuropsychiatric inventory questionnaire: comparison of Alzheimer's disease neuroimaging initiative and national Alzheimer's coordinating center cohorts

Paula T Trzepacz et al. Am J Geriatr Psychiatry. 2013 Jul.

Abstract

Objective: Neuropsychiatric symptoms are prevalent in mild cognitive impairment (MCI) and Alzheimer disease (AD) and commonly measured using the Neuropsychiatric Inventory (NPI). Based on existing exploratory literature, we report preliminary validation of three NPI Questionnaire (NPI-Q-10) subscales that measure clinically meaningful symptom clusters.

Methods: Cross-sectional results for three subscales (NPI-Q-4-Frontal, NPI-Q-4-Agitation/Aggression, NPI-Q-3-Mood) in amnestic MCI and AD dementia cases from the National Alzheimer's Coordinating Center (NACC) and Alzheimer's Disease Neuroimaging Initiative (ADNI) databases were analyzed using confirmatory unrotated principal component analysis.

Results: ADNI contributed 103 MCI, 90 MCI converters, and 112 AD dementia cases, whereas NACC contributed 1,042 MCI, 763 MCI converters, and 3,048 AD dementia cases. NACC had higher baseline mean age (75.7 versus 74.6), and more impaired mean scores (at month 24) on Mini-Mental State Exam (19.5 versus 22.4) and NPI-Q-10 (5.0 versus 4.3), and all NPI-Q subscales than ADNI. Medians were not different between cohorts for NPI-Q-4-Agitation/Aggression, and NPI-Q-3-Mood, however. Each item on all scales/subscales contributed variance in principal component analysis Pareto plots. All items in Factor (F) 1 for each scale/subscale projected in a positive direction on biplots (revealing coherence), whereas F2 and F3 items showed more spatial separation (revealing independence). There were remarkable similarities between cohorts for factor loadings and spatial patterns of item projections, although factor item identities varied somewhat, especially beyond F1.

Conclusion: The similar pattern of results across two cohorts support validity of these subscales, which are worthy of further psychometric evaluation in MCI and AD patients and preliminary application in clinical settings.

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Conflict of interest statement

Disclosures: Drs. Trzepacz, Dennehy, Yu and Willis, and Mr. Bhamditipati and Mr. Jia Sun are full-time salaried employees and minor shareholders of Eli Lilly and Company.

Dr. Saykin receives support from the NIH National Institute on Aging (R01 AG19771 as PI; P30 AG10133 Indiana ADC as Imaging Core leader; U01 AG024904 and RC2 AG036535 as ADNI Genetics Core leader; and U01 AG032984 Alzheimer's Disease Genetics Consortium as site PI).

Dr. Cummings has provided consultation to Abbott, Acadia, Acerra, ADAMAS, Anavex, Astellas, Avanir, Baxter, Bristol-Myers Squibb, Eisai, Elan, EnVivo, Forest, Genentech, GlaxoSmithKline, Janssen, Lilly, Lundbeck, Medivation, Medtronics, Merck, Neurokos, Novartis, Pfizer, Prana, QR, Sonexa, Takeda, and Toyama pharmaceutical companies and Bayer, Avid, GE, MedAvante, Neurotrax, and UBC Assessment Companies. Dr. Cummings owns stock in ADAMAS, Prana, Sonexa, MedAvante, Neurotrax, Neurokos, and QR pharma and owns the copyright of the Neuropsychiatric Inventory scale. He is a speaker/lecturer for Eisai, Forest, Janssen, Novartis, Pfizer, Lundbeck.

Figures

Figure 1
Figure 1
Boxplots are shown for groups for MMSE, NPI-Q-10 and NPI-Q subscales at the last visit in NACC and 24-month visit in ADNI cohorts. Group sizes varied. The thick black lines show the median; the box is draw between the quartiles (25%-75%); the whiskers extend to the most extreme data point which is no more than 1.5 times the interquartile range (IQR) from the box, which correspond to the ±2.698 multiple standard deviation.
Figure 2
Figure 2
Pareto plots of the percentage of variance contributed by each factor based on principal component analyses for the ADNI and NACC cohorts for the NPI-Q-10 and NPI-Q subscales.
Figure 3
Figure 3
Gabriel biplots are visual representations of the relationships between item factor loadings when plotted between pairs of factors because directionality offers additional information about scales and subscales. Biplots are shown for each of the NPI-Q-10 and NPI-Q subscales for the ADNI (left) and NACC (right) cohorts. Biplots are 2-dimensional graphic representations of items' factor loadings and display all of the combinations between pairs for the first three factors from PCA analyses. The top two rows of all figures plot item loading values for Factor 1 along the x-axis against those for either Factor 2 or 3 along the y axis. In the third row of all graphs, Factor 2 item values are plotted along the x axis and those for Factor 3 along the y axis. In all graphs of Factor 1's items with either Factor 2 or 3, all values point in a positive direction (ie, pointing within the right half of the circles). However, when Factors 2 and 3 are plotted with each other, the items point in both positive and negative directions. (Abbreviations for NPI-Q items are coded using letters listed in Table 2.)
Figure 3
Figure 3
Gabriel biplots are visual representations of the relationships between item factor loadings when plotted between pairs of factors because directionality offers additional information about scales and subscales. Biplots are shown for each of the NPI-Q-10 and NPI-Q subscales for the ADNI (left) and NACC (right) cohorts. Biplots are 2-dimensional graphic representations of items' factor loadings and display all of the combinations between pairs for the first three factors from PCA analyses. The top two rows of all figures plot item loading values for Factor 1 along the x-axis against those for either Factor 2 or 3 along the y axis. In the third row of all graphs, Factor 2 item values are plotted along the x axis and those for Factor 3 along the y axis. In all graphs of Factor 1's items with either Factor 2 or 3, all values point in a positive direction (ie, pointing within the right half of the circles). However, when Factors 2 and 3 are plotted with each other, the items point in both positive and negative directions. (Abbreviations for NPI-Q items are coded using letters listed in Table 2.)
Figure 3
Figure 3
Gabriel biplots are visual representations of the relationships between item factor loadings when plotted between pairs of factors because directionality offers additional information about scales and subscales. Biplots are shown for each of the NPI-Q-10 and NPI-Q subscales for the ADNI (left) and NACC (right) cohorts. Biplots are 2-dimensional graphic representations of items' factor loadings and display all of the combinations between pairs for the first three factors from PCA analyses. The top two rows of all figures plot item loading values for Factor 1 along the x-axis against those for either Factor 2 or 3 along the y axis. In the third row of all graphs, Factor 2 item values are plotted along the x axis and those for Factor 3 along the y axis. In all graphs of Factor 1's items with either Factor 2 or 3, all values point in a positive direction (ie, pointing within the right half of the circles). However, when Factors 2 and 3 are plotted with each other, the items point in both positive and negative directions. (Abbreviations for NPI-Q items are coded using letters listed in Table 2.)
Figure 3
Figure 3
Gabriel biplots are visual representations of the relationships between item factor loadings when plotted between pairs of factors because directionality offers additional information about scales and subscales. Biplots are shown for each of the NPI-Q-10 and NPI-Q subscales for the ADNI (left) and NACC (right) cohorts. Biplots are 2-dimensional graphic representations of items' factor loadings and display all of the combinations between pairs for the first three factors from PCA analyses. The top two rows of all figures plot item loading values for Factor 1 along the x-axis against those for either Factor 2 or 3 along the y axis. In the third row of all graphs, Factor 2 item values are plotted along the x axis and those for Factor 3 along the y axis. In all graphs of Factor 1's items with either Factor 2 or 3, all values point in a positive direction (ie, pointing within the right half of the circles). However, when Factors 2 and 3 are plotted with each other, the items point in both positive and negative directions. (Abbreviations for NPI-Q items are coded using letters listed in Table 2.)
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