How Well Do the ADAS-cog and its Subscales Measure Cognitive Dysfunction in Alzheimer’s Disease?

Abstract

Background/Aims: The Alzheimer’s Disease Assessment Scale-cognitive (ADAS-cog) is regularly used to assess cognitive dysfunction in Alzheimer’s disease (AD) clinical trials. Yet, little is known about how the instrument and its subscales measure cognition across the spectrum of AD. The current investigation used item response theory (IRT) analyses to assess the measurement properties of the ADAS-cog across the range of cognitive dysfunction in AD. Methods: We used IRT-based analyses to establish the relationship between cognitive dysfunction and the probability of obtaining observed scores on each subscale and the test as a whole. Data were obtained from 1,087 patients with AD and amnestic mild cognitive impairment. Results: Results showed that the ADAS-cog and its subscales provide maximum information at moderate levels of cognitive dysfunction. Raw score differences toward the lower and higher ends of the scale corresponded to large differences in cognitive dysfunction, whereas raw score differences toward the middle of the scale corresponded to smaller differences. Conclusions: The utility of the ADAS-cog and its subscales is optimal in the moderate range of cognitive dysfunction, but raw score differences in that region correspond to relatively small differences in cognitive dysfunction. Implications for tracking and staging dementia and for clinical trials are discussed.

Efficacy of a medical food on cognition in Alzheimer's Disease: Results from secondary analyses of a randomized, controlled trial

“…these observations are in line with recent publications that bring into question the sensitivity of adascog in mild cognitive impairment and mild ad (17)(18)(19). this may be due to the poor psychometric properties of the adascog measure, such as inadequate assessment of cognitive domains such as attention, working memory and executive function (19,20) and the presence of floor effects (17). Furthermore, several recent studies have reported slower rates of placebo decline in ad patients than traditionally assumed by older models and clinical trials (12,(21)(22)(23); they have also shown that baseline adas-cog significantly affects the rate of ad progression (23,24).…”

“…Within the group of patients with higher adas-cog scores at baseline, souvenaid significantly improved adas-cog scores compared with the control group. these observations are in line with recent publications that bring into question the sensitivity of adascog in mild cognitive impairment and mild ad (17)(18)(19). this may be due to the poor psychometric properties of the adascog measure, such as inadequate assessment of cognitive domains such as attention, working memory and executive function (19,20) and the presence of floor effects (17).…”

A phase 2 randomized trial of ELND005, scyllo-inositol, in mild to moderate Alzheimer disease

“…19,35 The ADAS-Cog is most sensitive to change in patients with moderate disease. 36,37 Since the NTB captures changes in delayed memory and executive function which are not well-covered by the ADAS-Cog, our findings support the choice of the NTB for studies in mild AD.…”

Measuring Therapeutic Efficacy in Patients with Alzheimer’s Disease: Role of Instruments

“…Considering the difference in underlying neural networks, it is likely that sensitivity to change on enhancement of neurotransmission is different for these aspects even though they are summarized as ‘cognition’. It has already been reported that the ADAS-cog and its subscales provide maximum information at moderate levels of cognitive dysfunction [3]. Raw score differences toward the lower and higher ends of the scale corresponded to large differences in cognitive dysfunction, whereas raw score differences toward the middle of the scale corresponded to smaller differences [3].…”

“…It has already been reported that the ADAS-cog and its subscales provide maximum information at moderate levels of cognitive dysfunction [3]. Raw score differences toward the lower and higher ends of the scale corresponded to large differences in cognitive dysfunction, whereas raw score differences toward the middle of the scale corresponded to smaller differences [3]. In fact, in more severe stages of disease the ADAS-cog loses its sensitivity of change so much that the severe impairment battery was developed to assess patients who are unable to complete tests such as the ADAS-cog [24].…”