Apparently Healthy, but Diagnosed With Alzheimer’s?

Determining whether someone has Alzheimer’s disease usually requires an extended diagnostic process. A doctor takes a patient’s medical history, discusses symptoms, administers verbal and visual cognitive tests.

The patient may undergo a PET scan, an M.R.I. or a spinal tap — tests that detect the presence of two proteins in the brain, amyloid plaques and tau tangles, both associated with Alzheimer’s.

All of that could change dramatically if new criteria proposed by an Alzheimer’s Association working group are widely adopted.

Its final recommendations, expected later this year, will accelerate a shift that is already underway: from defining the disease by symptoms and behavior to defining it purely biologically — with biomarkers, substances in the body that indicate disease.

The draft guidelines, Revised Criteria for Diagnosis and Staging of Alzheimer’s Disease, call for a simpler approach. That could mean a blood test to indicate the presence of amyloid. Such tests are already available in some clinics and doctors’ offices.

“Someone who has biomarker evidence of amyloid in the brain has the disease, whether they’re symptomatic or not,” said Dr. Clifford R. Jack Jr., the chair of the working group and an Alzheimer’s researcher at the Mayo Clinic.