Alzheimer's Diagnostic Test, Misleading the Reader?

Contributed by: Dennis Fortier, President, Medical Care Corporation

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The popular press carries more stories like this in a given week than we could possibly highlight in this blog.

I am referring to this article describing a diagnostic test for Alzheimer's disease.  The test measures proteins in the spinal fluid and, according to the company with hopes of one day commercializing the test, it can diagnose Alzheimer's disease with 90% accuracy.  I believe that is a scientifically plausible claim and I suspect that careful measures of various biomarkers will achieve such accuracy in the very near future.

The potentially misleading element of this story comes from the following quote:

"Right now, diagnostic accuracy for Alzheimer's disease can be as low as 70 percent, meaning three out of 10 people who are diagnosed with this disease might not actually have Alzheimer's disease, but rather some other kind of dementia".

It is true that diagnostic accuracy for AD "can be" as low as 70 percent, if a physician does not follow published guidelines for working up a memory complaint.  However, when published guidelines are followed, then diagnostic accuracy is already better than the 90% target for which this new test is striving.

I think this test, and others, may pan out, but let's not mischaracterize the problem.  We need to help physicians update their knowledge to keep pace with the constant advances in medicine.  A new test, with inferior accuracy to the already achievable standard, is not a breakthrough, and the word "promising" probably does not belong in the story's headline.

Combining a Brain Scan with a Spinal Fluid Test

Contributed by: Dennis Fortier, President, Medical Care Corporation
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According to a study published in the latest issue of Archives of Neurology, researchers at University College London's Institute of Neurology have collected evidence of a correlation between two interesting brain pathologies. The research looked at low levels of beta-amyloid in the spinal fluid and, based on an MRI brain scan twelve months later, the rate of brain atrophy (or shrinkage).

The interest in this study stems from prior research showing that a low level of amyloid in the cerebral spinal fluid (CSF) is a common (but not certain) precursor to Alzheimer's disease. Furthermore, typical Alzheimer's pathology includes the death of brain cells leading to brain shrinkage. Therefore, noting that these two indicators seem to move in unfavorable directions, even before symptoms are present, might lead to methods for earlier detection and intervention.

In general, the expert research community supports the notion of combining indicators to detect early trends that should be carefully monitored. While this study is certainly noteworthy, coverage in the media, that has portrayed these findings as a method for detecting early stage Alzheimer's disease, is probably over-stated at this early point.
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