CHICAGO — A simple blood test could soon allow clinicians to diagnose Alzheimer's disease accurately.
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 this, the test could be on the market by mid-fall, Dr. Louis Kirby said at the International Conference on Alzheimer's Disease.
An easy blood test that would diagnose early Alzheimer's could have enormous impact, said Dr. Kirby, whose company, Provista Life Sciences, owns the patent.
The test, to be marketed as LymPro, assumes that lymphocytes mirror a unique neuronal cell-cycle dysregulation seen in Alzheimer's patients, Dr. Kirby said at the meeting presented by the Alzheimer's Association. “Normally, neurons divide and mature, and then remain active for decades without dividing again. A great deal of relatively new research suggests 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 then unable to redifferentiate. Researchers have concluded that the neurons then either die or produce Alzheimer's pathology (research summary—Biochim. Biophys. Acta 2007;1772:413-21).
Research also suggests that peripheral lymphocytes in Alzheimer's patients display a similar cell-cycle defect when exposed to a mitogenic stimulus, Dr. Kirby said. 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. In fact, this study found that the expression of CD-69 inversely correlated with the level of dementia as measured by the Mini-Mental State Examination score (Neuroreport 2001;12:3969-72).
Dr. Thomas Arendt, of the University of Leipzig (Germany), was the lead investigator on many of these studies. He developed the LymPro test and has licensed the technology to Dr. Kirby's Arizona-based company.
Dr. Kirby's 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 between controls, Alzheimer's, and Parkinson's patients based on variations in the CD-69 levels, Dr. Kirby said. The test had 91% sensitivity and a 92% specificity, with an overall accuracy of nearly 97%.
And, Dr. Kirby said, since the blood test score correlated with the level of dementia on 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.”