As every disease area pins its hopes on blood biomarkers, it is instructive to see what these tests are actually being used for in Alzheimer’s.

It strikes me that the current usage of blood biomarkers in dementia will be a crutch that is immensely helpful for patients and clinicians to take patient’s future risk of dementia seriously. Patients can easily initiate conversations about it; tests become a re-imburseable expense and so forth.

From a technological standpoint, we are not doing a more precise job of measuring dementia risk, and we are nowhere closer to capturing a more narrow biological process that better differentiates heterogeneous paths to developing dementia. The scope of equivalence between blood-biomarker based decisions and PET imaging based decisions is still narrow. The utility is primarily in cost-reduction without reducing accuracy, which is a big deal in terms of accessibility.

In the long run, we don’t yet know the price we will pay in terms of causal specificity for substituting the tissue of interest with blood and how that intersects with a wide swarth of the general population being measured instead of a targeted population.

The recommendations in the new CPG — both of which apply only to patients with cognitive impairment being seen in specialized care for memory disorders — are:

• BBM tests with ≥90% sensitivity and ≥75% specificity can be used as a triaging test, in which a negative result rules out Alzheimer’s pathology with high probability. A positive result should also be confirmed with another method, such as a cerebral spinal fluid (CSF) or amyloid positron emission tomography (PET) test.

• BBM tests with ≥90% for both sensitivity and specificity can serve as a substitute for PET amyloid imaging or CSF Alzheimer’s biomarker testing.

“Not all BBM tests have been validated to the same standard or tested broadly across patient populations and clinical settings, yet patients and clinicians may assume these tests are interchangeable,” said alz.org/press/spokespeo…, Alzheimer’s Association vice president of scientific engagement and a co-author of the guideline. “This guideline helps clinicians apply these tools responsibly, avoid overuse or inappropriate use, and ensure that patients have access to the latest scientific advancements.”