Predicting Conversion to Alzheimer Disease Using Standardized Clinical Information

OBJECTIVE: To identify aspects of a standardized clinical assessment that can predict which individuals within the category of "questionable" Alzheimer disease (AD) have a high likelihood of converting to AD over time. DESIGN: Detailed semistructured interviews were performed at baseline and annually for 3 years. SETTING: University-based gerontology research program. PATIENTS: The patient population consisted of 165 individuals 65 years and older: 42 of the participants had a Clinical Dementia Rating (CDR) of normal cognition (CDR rating, 0.0) and 123 had a rating of questionable AD (CDR rating, 0.5). After 3 years of follow-up, 23 of the 123 subjects with questionable AD were diagnosed with probable AD. MAIN OUTCOME MEASURES: The interview was used to generate a summary measure based on the sum of 6 CDR categories, known as the Total Box Score. The responses to 32 selected questions from the interview also were examined. RESULTS: Likelihood of progression to AD during the follow-up period was strongly related to the Total Box Score. For example, more than 50% of individuals with a Total Box Score of 2.0 or higher at baseline developed AD during the follow-up interval, whereas about 10% of individuals with a Total Box Score of 1.0 or lower developed AD during this same period. Selected questions from the standardized clinical interview also were highly predictive of subsequent conversion to AD among the study population. Eight selected questions from the clinical interview at baseline, combined with the CDR Total Box Score, identified 88.6% of such individuals accurately (questionable group, 82/91; converter group, 19/23). CONCLUSIONS: A standardized clinical assessment can be used to identify the subgroup of individuals within the category of questionable AD who have a high likelihood of converting to AD over time. Subjects who met the criteria for questionable AD had a variety of trajectories during a 3-year follow-up, suggesting that diverse factors may influence the functional changes observed in this population.