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.