An international team of scientists has developed a genetic test that can predict the age at which a person is likely to develop Alzheimer’s disease (AD).

The test allows the simultaneous analyses of multiple DNA sequences in order to provide a risk estimate. It uses information provided by the DNA analysis of over 70,000 AD patients and normal elderly individuals.

Validation of the test was published last week in PLOS Medicine.

“We combined genetic data from large, independent cohorts of patients with AD with epidemiological estimates to create the scoring, then replicated our findings on an independent sample and validated them with known biomarkers of Alzheimer’s pathology,” explained in a press release the co-first author Rahul S. Desikan, MD, PhD and clinical instructor in the UCSF Department of Radiology & Biomedical Imaging.

The team sought each individual genome, looking for what is called “single nucleotide polymorphisms (SNPs), DNA variations where only one nucleotide (A, T, G or C) differs. The goal was to identify specific differences between AD patients and normal elderly people.

This analysis allowed the researchers to discover thousands of SNPs associated with the disease. Out of them, the 31 strongest genetic markers were used for developing the tool.

The status of gene APOE, the most important genetic risk factor for AD, is among those markers. The E4 variant of this gene is associated with early onset of the disease.

That said, the test was able to predict the age of onset even among people who did not have the APOE E4 allele. Individuals with a high score developed AD 10 to 15 years earlier than individuals with a low score, according to the study.

Neuronal death slowly takes place in the brain several years prior to the first symptoms of AD. A fully validated test that predicts the risk of developing AD would not only allow early diagnostic and prognostic, but be useful in clinical trials, added M. Desikan.

To read the study, follow this link.