Wouters_2016_Int.J.Methods.Psychiatr.Res_25_190

Computerized Adaptive Testing (CAT) of cognitive function, selects for every individual patient, only items of appropriate difficulty to estimate his or her level of cognitive impairment. Therefore, CAT has the potential to combine brevity with precision. We retrospectively examined the evaluation of treatment effects of cholinesterase inhibitors by CAT using longitudinal data from 643 patients from a Dutch teaching hospital who were diagnosed with Alzheimer disease or Lewy Body disease. The Cambridge Cognitive Examination (CAMCOG) was administered before treatment initiation and after intervals of six months of treatment. A previously validated CAT was simulated using 47 CAMCOG items. Results demonstrated that the CAT required a median number of 17 items (inter-quartile range 16-20), or a corresponding 64% test reduction, to estimate patients' global cognitive impairment levels. At the same time, intraclass correlations between global cognitive impairment levels as estimated by CAT or based on all 47 CAMCOG items, ranged from 0.93 at baseline to 0.91-0.94 at follow-up measurements. Slightly more people had substantial decline on the original CAMCOG (N = 31/285, 11%) than on the CAT (N = 17/285, 6%). We conclude that CAT saves time, does not lose much precision, and therefore deserves a role in the evaluation of treatment effects in dementia. Copyright (c) 2015 John Wiley & Sons, Ltd.