DAD-6: A 6-ltem version of the Disability Assessment for Dementia scale which may differentiate Alzheimer's disease and mild cognitive impairment from controls

BACKGROUND

The need to detect early changes in instrumental activities of daily life led us to modify the Disability Assessment for Dementia Scale (DAD) by focusing on executive components of 6 instrumental items (DAD-6).

AIM

To evaluate the relevance of the DAD-6 for detecting early impairment in a nondemented population.

METHODS

The DAD-6 was administered to informants of 84 patients: 31 with mild dementia (MD), 53 with mild cognitive impairment (MCI) and 55 healthy controls.

RESULTS

DAD-6 scores gradually decreased with increasing severity of the cognitive status [18 in healthy controls vs. 15.1 ± 3.2 in MCI versus 9.6 ± 3.5 in MD, p < 0.0001). Receiver-operating characteristic curve analyses yielded an optimal cut score of 14 to distinguish MCI from MD with a sensitivity of 0.83 (95% confidence interval 0.74-0.92) and a specificity of 0.84 (0.71-0.94), and a cut score of 15 to distinguish single-domain MCI from multi-domain MCI with a sensitivity of 0.96 (0.90-0.99) and a specificity of 0.54 (0.33-0.75).

CONCLUSION

The DAD-6 reliably detects early loss of autonomy due to cognitive impairment.

Relevance of 10-min delayed recall in dementia screening

Within the context of early diagnosis of Alzheimer's disease (AD), there is a growing interest in neuropsychological screening tests. Amongst these tests, we focused on the largely used Memory Impairment Screen (MIS). The objective of the present work was to show that adding a 10-min delayed recall to the MIS, improves the test psychometric characteristics in order to detect dementia in the earliest stages. A prospective study was carried out on a cohort of 270 consecutive elderly ambulatory subjects attending the Broca Hospital Memory Clinic: normal controls (n = 67), mild cognitive impairment subjects (n = 98) and mildly demented patients [n = 105, Mini Mental State Examination (MMSE) = 23 +/- 4]. This study consisted in testing the advantage of the 10-min delayed recall entitled MIS-D compared with the MIS. At a cut-off score of 6, the MIS-D revealed satisfying psychometric characteristics with a sensitivity of 81% and a specificity of 91%, whilst the MIS alone indicated a sensitivity of 60% and a specificity of 88% in detecting dementia. In demented patients with MMSE score > or =26, MIS-D properties still remained satisfying (sensitivity: 75%, specificity: 92%). MIS-D is a more relevant screening test than MIS alone at very early stages of dementia.

Accidental MCI in healthy subjects: a prospective longitudinal study

A study was realized on 130 healthy and autonomous volunteers (60-80 years old) who met specific medical and functional inclusion criteria. A comprehensive battery of neuropsychological tests was performed at baseline (M0), 6 and 12 months (M6, M12). At M0 the results indicated that 65% were cognitively normal on each of all the neuropsychological tests, whereas 35% presented a cognitive deficit on one or more tests. At M12, 52% of the subjects who had a cognitive deficit at M0 remained impaired, whereas 48% normalized their scores: they performed as well as the subjects classified normal at M0. The results also indicated that the subjects who remained impaired at M12, had at M0 low scores on three tests or more, whereas the ones who normalized their scores had one or two failed tests. This study focuses on the risk of false positive cases and shows that low scores can be accidental. The authors propose decision rules allowing to reduce the risk of false positive cases. The observation of accidental impairment invites to be cautious and makes this 1-year follow-up study particularly relevant, since a 1-year follow-up is generally needed to diagnose very mild dementia.

The apolipoprotein E epsilon4 allele and the response to tacrine therapy in Alzheimer's disease

The objective of our study was to evaluate the effects of the apolipoprotein E (ApoE) phenotype and gender on the response to tacrine treatment in Alzheimer's disease (AD). ApoE phenotyping was performed on 76 patients treated with tacrine for AD. This group comprised 33 ApoE epsilon4 allele carriers (epsilon4+) and 43 non-epsilon4 carriers (epsilon4-). Patients were treated blindly in relation to the ApoE phenotype, with incremental tacrine dosages ranging from 40 mg/day up to the highest dosage (160 mg) tolerated without side-effects. At least 6 weeks elapsed between each increase. Changes in the scores for the Alzheimer Disease Assessment Scale-Cognitive Component (ADAS-Cog) between baseline and each increment in dosage were assessed in the epsilon4- and epsilon4+ groups. The cut-off point for being considered as responsive to tacrine treatment was a 4-point decrease in the ADAS-Cog score. There was no tendency for the epsilon4- carriers to respond better than the epsilon4+ carriers. When patients were stratified by gender, no differences were found between the effects of the treatment on men and women. Consequently, these results do not support the hypothesis that the ApoE phenotype and gender are predictors of the response to tacrine in AD patients.

Apolipoprotein E phenotypes in demented and cognitively impaired patients with and without cerebrovascular disease

Controversy exists regarding the apolipoprotein E (ApoE) epsilon4 allele association with vascular dementia (VaD), ranging from increased epsilon4 frequency, similar to that found for Alzheimer's disease (AD), to no association between the epsilon4 allele and VaD. To clarify further the relationship between ApoE alleles polymorphism and cerebrovascular disease (CVD) in demented and cognitively impaired patients, we examined the ApoE phenotypes in a sample of 280 patients: 155 with AD, 21 with VaD, 32 with mixed dementia (MD), 45 with mild cognitive impairment (MCI) but without CVD, and 27 in which vascular disease was the most probable cause of cognitive decline [vascular mild cognitive impairment (VMCI)]. Our results show that the frequency of the ApoE epsilon4 allele in patients over 70 years old with clinically diagnosed VaD and VMCI does not differ significantly from that of controls. In contrast, ApoE epsilon4 allele-bearing individuals had greater risk of having late-onset AD (OR = 8.8; 95% CI 3.7-21.0), or non-vascular cognitive impairment (OR = 7.0; 95% CI 2.5-19.0).

[Critical review of psychometric tests]

In this paper, a critical review of psychometric tests is proposed. The first part describes several aspects of modern, theoretical psychometry and the influence of cognitive psychology. The second part focuses on application of tests to dementia and preliminary results of a longitudinal study of cognitive evolution of patients with mild dementia. Based on this longitudinal study, the batteries of tests to be used for diagnosis, or experimental research, or clinical trials are described. The authors underline the fact that tests are not "good" or "bad" in themselves, and suggest a number of rules for selecting inclusion, evaluation and improvement criteria, related to drug treatment.