The term analyte is defined as a substance that a laboratory test seeks to detect (or analyze). I discovered many definitions for the term biomarker on the web but the one that I liked the most is the following: any molecular species found to provide correlation to a particular phenotype or perturbation of a biological system. Of particular interest to me was that many of the definitions for biomarker I encountered were specifically linked to the detection of cancer.
I believe that a common practice today is to use the term analyte for the detection of relatively simple elements or molecules such as serum chloride or liver enzymes and that the term biomarker has evolved out of genomic/proteomic science to describe new markers for specific diseases or groups of diseases. Although many biomarkers are used to diagnose malignant lesions, the term can equally apply to non-malignant diseases such as cardiovascular disease.
In the process of preparing this blognote on biomarkers, I came across a very interesting resource -- the Aetna Clinical Policy Bulletin on tumor markers dated March 1, 2005, that expresses Aetna's determination of whether certain services or supplies are medically necessary, experimental and investigational, or cosmetic. This document is extremely well written and worth reading if for no other reason than to understand the array of cancer biomarkers in clinical use today.
What I found very interesting in this document was that the use of cancer biomarkers was generally restricted to disease monitoring and follow-up for patients who already have been diagnosed with a tumor. For example, here is how the use of biomarkers for monitoring bladder tumors is described:
Aetna considers the bladder tumor antigen (BTA) Stat test, the nuclear matrix protein (NMP22) test, the fibrin/fibrinogen degradation products (Aura-Tek FDP) test, or the UroVysion fluorescent in situ hybridization (FISH) test medically necessary in any of the following conditions:
- Follow-up of treatment for bladder cancer; or
- Monitoring for eradication of bladder cancer; or
- Recurrences after eradication.
I have no argument with the science or business logic of this approach to cancer biomarkers. However, from a healthcare consumer's perspective, I would suggest that the underlying logic used by Aetna does not exactly make much sense. I think that consumers would argue that if a biomarker can efficiently detect recurrences of a tumor, it could also be used for wellness screening and the initial detection of cancer. This makes particular sense when the biomarker is used in concert with a physical examination and the ordering of appropriate imaging studies.
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