Neuropsychological prediction of conversion to dementia from questionable dementia: statistically significant but not yet clinically useful

Abstract

Background: Verbal memory impairment, one of the earliest signs of Alzheimer's disease (AD), may help identify people with cognitive impairment, insufficient for a diagnosis of dementia (questionable dementia: QD), at risk of developing AD. Other cognitive parameters have been found that may indicate which people with QD will go on to develop dementia. Nevertheless, some researchers have reported only partial success in differentiating between mild AD and age related cognitive impairment. Objectives: To discover if there are early, pre-clinical cognitive markers that could help identify patients attending our memory clinic who were at risk of developing dementia. Methods: Multidisciplinary assessment of a consecutive sample of 195 patients with QD seen in a National Health Service hospital outpatient clinic; 135 seen for a mean follow up of 24.5 months. Results: Conversion rate to dementia was 27.4% (37 of 135). A diagnosis of probable or possible AD was made in 15.6% (21 of 135) of cases. Despite statistically significant differences in some cognitive tasks between those who did and those who did not go on to dement, Cox regression analyses failed to improve prediction rates markedly above base rates and were unstable. Conclusion: A large number of studies claim good prediction of conversion to dementia using cognitive test scores. Although this study produced similarly good sensitivity and specificity values, proper consideration of the statistical analyses and their clinical significance suggested that these prediction methods are currently too imprecise for clinical use. Use of cognitive indicators combined with neuroradiological, neuropathological, and genetic factors for predicting conversion to dementia might prove more reliable but may be beyond the scope of many geriatric services.

Predictive Accuracy of MCI Subtypes for Alzheimer’s Disease and Vascular Dementia in Subjects with Mild Cognitive Impairment: A 2-Year Follow-Up Study

“…Indeed, 'amnestic MCI' had a low sensitivity as a prognostic test for the development of AD, whereas 'multiple domain MCI' had a high sensitivity. Other investigators also found MCI or related concepts such as CIND to be valid with regard to the development of dementia (mostly AD) [5,[22][23][24]. The low positive predictive value of the MCI subtypes found in our study may be because of the small number of cases of dementia diagnosed and the short follow-up.…”

Reduced benefit from mnemonic strategies in early-stage Alzheimer’s disease: a brief testing-the-limits paradigm for clinical practice

“…Single group comparisons by means of the MannWhitney U test revealed that AD patients had significantly higher failure rates in the post-tests than both MD and healthy individuals, whereas the scores of the MD and the HC groups did not differ. As expected from literature [6,14,65,68], analysis of the pre-test performances showed significant differences in failure rates only between AD and HC subjects, but not between AD and MD patients ( Table 2).…”

Neuropsychological markers of dementia in patients with memory complaints

“…Therefore, from a clinical point of view it is really important to know which variables can help the prediction of the future of each individual patient. In this sense, despite the methodological accuracy of some studies, their results are not always specific and consistent; and these results have only a predictive value for these only studies, but they can not be generalized and they do not have a clinical use (Tian et al, 2003).…”