Longitudinal study of CSF biomarkers in patients with Alzheimer's disease

Background

The CSF biomarkers tau and Aβ42 can identify patients with AD, even during the preclinical stages. However, previous studies on longitudinal changes of tau and Aβ42 in individual patients with AD and elderly controls report somewhat inconsistent results.

Methodology/Principal Findings

We investigated the levels of tau and Aβ42 at baseline and after 1 year in 100 patients with AD. In a second cohort of 45 AD patients we measured the CSF biomarkers at baseline and after 2 years. Moreover, in 34 healthy elderly controls the CSF biomarkers were followed for 4 years. The baseline levels of tau were increased with >60% in AD patients compared to controls (p<0.001), while baseline Aβ42 levels were decreased with >50% (p<0.001). In the AD group followed for 2 years, tau increased with 16% compared to the baseline levels (p<0.05). However, the levels of tau were stable over 4 years in the controls. The levels of Aβ42 did not change significantly over time in any of the groups. In the patients with AD, tau was moderately associated with worse cognitive performance already at baseline (p<0.05).

Conclusions/Significance

Tau and Aβ42 in CSF seem to reflect the underlying disease state in both early and late stages of AD. The slight increase in tau over time observed in the patients with AD is modest when compared to the relatively large difference in absolute tau levels between AD patients and controls. Therefore, these markers maintain their usefulness as state markers over time and might serve as surrogate markers for treatment efficacy in clinical trials.

Cube copying test in combination with rCBF or CSF A beta 42 predicts development of Alzheimer's disease

BACKGROUND/AIM

The aim was to identify subjects with incipient Alzheimer's disease (AD) among patients with mild cognitive impairment (MCI) using brief cognitive tests.

METHODS

A total of 147 MCI patients were followed for 4-6 years and the incidence of AD was 11.6%/year. At baseline, the cube copying test, clock drawing test, MMSE and measurements of regional cerebral blood flow (rCBF) and cerebrospinal fluid (CSF) beta-amyloid(1-42) (A beta (42)) were performed.

RESULTS

The cube copying test, but not the clock drawing test, could predict AD among MCI patients with an area under the receiver operating characteristic curve of 0.64 (p < 0.01). The relative risk for future AD was increased in MCI subjects with impaired cube copying test (sex- and age-adjusted hazard ratio = 1.8, p < 0.05) and the incidence of AD was 18.2% in this subgroup. Combining the cube copying test with either rCBF or CSF A beta(42) had additive effects on the risk assessment for future development of AD. MCI patients achieving high scores on both MMSE and cube copying test had a very low risk of developing AD (incidence of AD = 1.6%).

CONCLUSION

In conclusion, combinations of the cube copying test with MMSE, rCBF and CSF A beta (42) measurements can identify subgroups of MCI subjects with either substantially reduced or increased risk for future development of AD.

Cerebrospinal fluid biomarkers predict decline in subjective cognitive function over 3 years in healthy elderly

OBJECTIVE

To investigate whether cerebrospinal fluid (CSF) biomarkers can predict cognitive decline in healthy, elderly individuals as they have been shown to do in cognitively impaired patient samples.

METHODS

In this study, 57 controls were tested for CSF biomarkers at baseline and then cognitively followed over 3 years.

RESULTS

Low levels of baseline beta-amyloid 1-42 (Abeta42) were associated with development of subjective memory impairment affecting quality of life (memQoL), with a worse Mini Mental Status Examination score and with inability to live in regular housing at follow-up (p < 0.05). The combination of baseline Abeta42 and phosphorylated tau (P-tau) was found to predict development of pathological memQoL with a sensitivity of 71.4% and a specificity of 75.7 (<0.01).

CONCLUSION

Low Abeta42 and combined Abeta42 and P-tau predicted subjective cognitive decline in healthy individuals. In summary, this study shows that already in the clinically normal population Alzheimer-disease-related biological signs might be detectable.