Sensitivity to change of composite and frequency scores of the neuropsychiatric inventory in mild cognitive impairment

Abstract

Background: The most appropriate means of capturing data from the Neuropsychiatric Inventory (NPI) must be understood to optimize use of this instrument in clinical trials. The utility of the composite score (frequency times severity) was recently demonstrated in mild and moderate dementia. Determination of frequency compared to composite scores in mild cognitive impairment (MCI) warrants investigation.

Methods: We used the NPI data from a randomized, placebo-controlled, multi-center, 24-week, clinical trial involving 160 patients who were diagnosed with amnestic MCI and had clinically significant neuropsychiatric symptoms (NPS). We calculated standardized changes for both frequency and composite scores.

Results: There were improvements in NPI composite scores in both active drug- and placebo-treated patients, with significant superiority of active drug. Standardized changes in severity and composite scores tended to be larger than those in the frequency scores, whereas discrimination between treatment groups was similar for all three scores.

Conclusions: Our findings support the hypothesis that in MCI, as in dementia, the NPI frequency score is not more sensitive to treatment-related change than the composite score. As the severity score adds information, the use of the composite score has better performance characteristics.