Spinal Fluid Tests: Who Are They Really Good For?

Posted August 11, 2010

A NYT article about the value of using spinal fluid tests to determine the presence of Alzheimer’s disease is optimistic and hopeful but maybe too much so.

In an article published yesterday, Gina Kolata writes “Researchers are finding simple and accurate ways to detect Alzheimer’s long before there are definite symptoms. In addition to spinal fluid tests they also have new PET scans of the brain that show the telltale amyloid plaques that are a unique feature of the disease.” And “Although the latest PET scans for Alzheimer’s are not commercially available, the spinal fluid tests are. So the new results also give rise to a difficult question: Should doctors offer, or patients accept, commercially available spinal tap tests to find a disease that is yet untreatable?”

The article raises a variety of complex subjects around early diagnostics. We have blogged about “early detection” issues recently and discussed the popular media topic of “is it good to know what you have before you can cure it?” story. We have commended the research community for the development of new early detection techniques and new categories to describe pre-clinical, early signs and full involvement phases of Alzheimer’s disease FOR RESEARCH PURPOSES ONLY.

One researcher not connected with the study is quoted in the NYT article as saying: “This (spinal fluid test) is what everyone is looking for, the bull’s-eye of perfect predictive accuracy.”

Good sound bite; not an accurate interpretation of the data in the paper to which the NYT article refers.

The study in Tuesday’s Archives of Neurology includes a limited number of patients, and would have to be carried out long enough to check whether the subgroup of cognitively normal subjects who were positive for the test later get AD. Otherwise, it would be too early to use this test as a sole diagnostic for AD. At this point, the data would only warrant potential use of the spinal tap test as a “differential” diagnostic to help diagnose AD in a patient already presenting with dementia, similar to how APOE4 gene testing is used now.

The use of brain scans and other biomarkers or physical indications of the presence of AD pathology is critically important for research into how AD pathology originates, progresses and ultimately how it can be stopped; but the clinical use of these biomarkers with the general population to predict or determine the presence of Alzheimer’s is premature.

As we have written before in this blog:

“It is so easy — and we believe wrong — to hail a fundamental advance in research as having immediate clinical benefits when there are none at this moment. So, the net effect is to tarnish an excellent approach to useful research that will ultimately help to bring relief to patients and their families with sensational and exaggerated claims or suggested impact.”

Articles like this draw considerable media attention and can give the general public the wrong impression that there is a clear and clinically appropriate way to diagnose Alzheimer’s.  Instead, this good research should be heralded for its contribution to understanding the disease and the significant role it will play in determining the path to a cure.

This study is hopeful and optimistic but more for the research value than for immediate help for AD patients.

Read the full piece in the NYT>

ABC News agreed with us. See the segment here>