A group of experts is proposing wider criteria for diagnosing Alzheimer's disease, so that the illness can be pinpointed earlier to allow more patients to try drug treatments and take part in clinical trials.
Alzheimer's, the most common form of dementia, is a fatal brain disease that can only be fully confirmed through post-mortem examination. It's typically diagnosed in living patients by examining a patient's history of memory loss, and then eliminating other possible causes.
But in a paper published this week in The Lancet Neurology, the International Working Group for New Research and Criteria for the Diagnosis of Alzheimer's Disease propose that Alzheimer's be defined as a "clinical-biological syndrome."
That would allow doctors to diagnose the illness based on biomarkers, from MRI or PET brain scans or cerebrospinal fluid analysis, even if patients didn't have clinical symptoms of dementia.
Under their proposed definition, a patient would have at least one positive biomarker along with "episodic memory impairment," which is the declining ability to recall memories of recent experiences.
The working group, led by Bruno Dubois, Salpêtrière Hospital, Paris, France, notes that the earliest stages of Alzheimer's can begin about 10 years before actual dementia sets in. That early stage is widely seen as the best time to intervene in Alzheimer's with medications that could slow the disease.
"…There is no longer a reason to wait until patients have developed full-blown dementia or to exclude from diagnosis and treatment a large number of patients who lack functional disability yet express the disease," they write in the Lancet position paper.
Several large clinical trials of potential Alzheimer's drugs have failed in recent years, but many experts say that may be because they were tested in people whose brains had already been too damaged by the disease. Some worry that these failures may dissuade drug companies and government institutions from investing further in research.
Lon Schneider from the University of Southern California Alzheimer's Disease Research Center in Los Angeles, writes in an accompanying comment that widening the definition of the disease to include the predementia phase would encourage further research.
"The simplicity of these criteria will be appealing to clinical trialists because they provide a broad range of diagnoses for Alzheimer's disease that can potentially be included in product labelling," Schneider writes.
But he adds: "field trials are needed to establish whether the diagnostic criteria will work effectively in clinical or research situations," since some biomarkers are also associated with other neurodegenerative and vascular diseases.
