Values of the Minimal Clinically Important Difference for the Neuropsychiatric Inventory Questionnaire in Individuals with Dementia.
OBJECTIVES
To estimate the minimal clinically important difference (MCID) for the Neuropsychiatric Inventory Questionnaire (NPI-Q), a widely used measure of behavioral and psychological symptoms of dementia (BPSDs) and associated caregiver stress.


DESIGN
Ten registered nurses rated the severity of BPSDs and caregiver distress using the NPI-Q during six monthly assessments and an external reference, a 7-point Likert-type global rating of BPSDs change during five monthly assessments from the second to the sixth month. An anchor-based (global ratings of change) approach and a distribution-based (standard error of measurement) approach were used to determine the MCID for the NPI-Q severity and distress subscales.


SETTING
Long-term care facility.


PARTICIPANTS
Nonbedridden residents with dementia (n = 45) and registered nurses (n = 10).


MEASUREMENTS
NPI-Q (severity and caregiver distress subscales) and global ratings of changes in BPSDs on a 7-point Likert-type scale.


RESULTS
The NPI-Q MCID ranges were 2.77 to 3.18 for severity and 3.10 to 3.95 for distress. Residents in the highest NPI-Q tertile at baseline had higher MCID severity (3.62) and distress (5.08) scores than those in the lowest tertile (severity (2.40), distress (3.10)).


CONCLUSION
This study provides an estimate of the MCID for severity and distress subscales of the NPI-Q, which can help clinicians and researchers determine whether NPI-Q change scores within a group of individuals with dementia are beyond measurement error and are clinically important.