Dawn of the Age of the Alzheimer's blood test

We've written periodically about the promise of blood tests to detect Alzheimer's disease, even in very early stages.  That promise is being fulfilled, but there are some rubs.

A few blood tests for beta amyloid have now been through clinical trials, and we even have at least one that detects tau protein of the type associated with Alzheimer's disease.  These tests are extremely helpful, because they will bypass the need for PET scans and MRIs that are currently used to identify biomarkers.  Recall that biomarker evidence is required for a reliable diagnosis of Alzheimer's disease.  As we said in Beating the Dementia Monster, my care team found a biomarker of atrophy of my brain in a series of MRIs, and they used this in my diagnosis.  

In the recent Alzheimer's Association International Congress (San Diego, July 31 -- August 4), the Alzheimer's Association Global Workgroup released their recommendations on the use of blood tests, noting that the tests aren't ready for prime time.  At least not as a standalone diagnostic tool.

So what's the problem?  Clinical trials have generally been carried out with homogeneous, largely white populations.  It's well known that Alzheimer's disease sometimes proceeds differently in different populations, creating uncertainty about how test results are to be interpreted.  Also, more needs to be known about how comorbidities and medications will influence test results.  So the Global Workgroup developed its recommended guidelines to account for these uncertainties.  It is expected that the guidelines will be adjusted on a regular basis as more is known about the tests.

For now, the guidelines would limit blood biomarker use to people with cognitive symptoms who are seen in specialist memory clinics and, ideally, receive follow-up with amyloid-PET or CSF to confirm they really do have amyloid plaques in the brain.  This is likely to be most common in clinical trials for new treatments.  They specifically recommend against using the tests in a primary care setting.  The guidelines also consider the relationship with comorbidities, especially kidney dysfunction. 

So far, I haven't seen anyone commenting on my concern.  What does this do to long-term care insurance?  When I signed up, I went through a pretty rigorous evaluation.  This was long before I had any suspicion I had Alzheimer's disease, but I could tell from the cognitive tests that they were interested in my memory and cognition.  Since blood tests appear to detect the disease in early stages, I'm thinking that, should insurance companies be permitted to use the tests to evaluate prospective policy holders, there are a lot of people who will have a very difficult time getting insured.