Blood Biomarker Associated with Risk of Alzheimer Disease

Increased levels in the blood of a specific biomarker are significantly associated with the prevalence and severity of Alzheimer disease (AD), but not with the risk of onset of new disease.

The protein clusterin, also known as apolipoprotein J, have been found to be increased in brain and cerebrospinal fluid of patients with AD, and have been suggested to be involved in the pathogenesis of AD.

Scientists at Erasmus University Medical Center (Rotterdam, The Netherlands) analyzed the plasma levels of clusterin measured at baseline from 1997 to 1999, in 60 individuals with prevalent AD, a random subgroup of 926 participants, and an additional 156 participants diagnosed with AD during the average 7.2 years of follow-up, until January 2007. Clusterin levels were analyzed via multiplex immunoassay on a human multianalyte profile at the Rules-Based Medicine's multiplexed biomarker testing laboratory, (Austin, TX, USA). The lowest detectable level was 1.3 μg/mL. The intra-assay variability was less than 4% and the interassay variability was less than 13%.

The scientists found that the likelihood of prevalent AD increased with increasing plasma levels of clusterin, with the odds increased by 63% for every standard deviation increase in clusterin levels, after adjusting for age, sex, education level, apolipoprotein E status, diabetes, smoking, coronary heart disease, and hypertension. Among patients with AD, higher clusterin levels were associated with more severe disease. There was no statistically significant association of plasma clusterin levels with new AD during total follow-up or with new AD within or after three years of baseline. The results for all-cause dementia and vascular dementia were similar.

The authors of study concluded that the data from the general population show that increased plasma-clusterin levels are associated with prevalent AD and are higher in more severe cases of AD. However, increased levels of clusterin do not precede development of AD and therefore are not a potential early marker of subclinical disease. The study was published in the April 2011 edition of the Journal of the American Medical Association (JAMA).

Related Links:
Erasmus University Medical Center
Rules-Based Medicine