Informant characteristics influence Clinical Dementia Rating Sum of Boxes scores-based staging of Alzheimer's disease.

The Clinical Dementia Rating Sum of Boxes (CDR-SB) is a staging scale for Alzheimer's disease (AD)1 and is commonly used as an outcome in clinical trials2. It relies on information provided by the patient and an informant3. The CDR-SB should reflect only the patient's disease severity. However, we explored whether informant characteristics were associated with CDR-SB scores because that association might introduce bias in Alzheimer's disease research. We found that the CDR-SB was 0.20 higher when informants were female, 0.39 higher when the informant was a patient's child and 0.18 lower if the relationship was other than spouse or children. Regarding the frequency of contact, CDR-SB scores were 0.38 higher when contact was at least once a week, 0.65 higher when daily and 0.57 higher when living with the patient. Our analysis results suggest that informant characteristics can modify the CDR-SB scores and might introduce bias into Alzheimer's disease trials and research.