Blood test may identify Alzheimer's disease

A simple blood test could soon allow clinicians — even primary care physicians — to diagnose Alzheimer’s disease accurately if a final validation study succeeds as optimistic researchers hope.

In an initial study of 88 patients, the test findings agreed with expert clinical diagnosis more than 90% of the time and had an overall accuracy of 97%. If the validation study confirms these results, the test could be on the market by mid-fall, said at the International Conference on Alzheimer’s Disease.

An easy blood test for early Alzheimer’s could have enormous impact. “Primary care physicians see the vast majority of patients with memory complaints, yet they are much less well-equipped [than are neurologists] to make an accurate diagnosis of Alzheimer’s. The introduction of this test will give them the tools they need to help these patients as early as possible.”

The test, to be marketed as LymPro, assumes that lymphocytes mirror a unique neuronal cell-cycle dysregulation seen in Alzheimer’s patients, said at the meeting presented by the Alzheimer’s Association. “Normally, neurons divide and mature, and then remain active for decades without dividing again.” Recent research “suggest that in Alzheimer’s disease, neurons prepare to reenter the cell division process in an abnormal fashion.” Neurons that undergo this change proceed almost to mitosis but are unable to redifferentiate. The neurons then die or produce Alzheimer’s pathology.

Peripheral lymphocytes in Alzheimer’s patients display a similar cell-cycle defect when exposed to a mitogenic stimulus. A 2001 study found that these lymphocytes were less able to express CD-69, a marker of white cell growth and proliferation, than lymphocytes from control patients. The expression of CD-69 inversely correlated with the level of dementia as measured by the Mini-Mental State Examination score.

The University of Leipzig, Germany, was lead investigator on many of these studies. Developed the Lympro test and has licensed the technology to Arizona-based company.

Initial study included 88 patients: 32 with probable Alzheimer’s disease, 26 with Parkinson’s dementia, and 30 cognitively intact controls. All diagnoses were based on clinical testing and observation by dementia experts.

After applying a mitogenic stimulus to the peripheral lymphocytes in each blood sample, researchers could reliably differentiate with controls. Alzheimer’s, and Parkinson’s patients based on variations in the CD-69 levels. The test had 91% sensitivity and 92% specificity, with an overall accuracy of nearly 97%.

The blood test score correlated with the level of dementia as rated by the Mini-Mental State Examination. “We have confidence that we should be able to dial back the diagnosis into the mild cognitive impairment stage, and — hopefully — even into the preclinical state.”

This level of disease prediction would require much more research, but he insisted that the possibility of extremely early diagnosis remains a strong one.