VALIDITY AND RELIABILITY OF THE ALZHEIMERS-DISEASE COOPERATIVE STUDY - CLINICAL GLOBAL IMPRESSION OF CHANGE

This article reports the development and psychometric properties of th e Alzheimer's Disease Cooperative Study-Clinical Global Impression of Change (ADCS-CGIC). At present, a number of unvalidated CGIC scales ar e used in clinical trials, with various methods for making ratings. Th e ADCS-CGIC was designed on the basis of a survey of ADCS clinicians a nd by adapting existing instruments. It includes an organized but unst ructured format, with which a clinician can address clinically relevan t change. The instrument's reliability and validity were assessed in a prospective trial of Alzheimer's disease (AD) and healthy subjects ov er a 12-month period. It showed good short-term reliability at 1 and 2 months, with 90 and 94% of AD subjects, respectively rated as having changed not at all or only minimally. The ADCS-CGIC's face validity wa s demonstrated by untreated AD subjects rated as having worsened over time at both 6 months (56% rated as having worsened) and 12 months (81 % rated as having worsened), whereas only 2% of control subjects showe d minimal worsening. As a measure of predictive validity, ADCS-CGIC ra tings at 12 months were significantly associated with change on four s everity scales. As with other measures, change ratings were sensitive to dementia severity. Moderately impaired subjects showed greater wors ening than other subjects. ADCS-CGIC ratings of greater worsening were made after the informant interview, regardless of whether informants or subjects were interviewed first. The ADCS-CGIC is a valid and relia ble instrument for use in clinical trials.