The Biomarker Discovery Experiment

There are two main points we have to keep in mind before starting a biomarker discovery experiment. 

Example Let us look at one example of this process currently used in medicine the example that we will use is the control of diabetes in patients. For a number of reasons glucose and not insulin concentration is used to monitor this disease. The effect of a small amount of the hormone insulin can cause a big change in the concentration of glucose in the blood, which is easily monitored and provides an effective biomarker for monitoring control of this condition for both types of the diabetes (types I and II) (Chart 1). 

This is a complicated question but one that must be thought about. The number of single biomarker assays that are failing in the market is high, and the FDA in the United States has not approved a single biomarker assay in the last year. The reason for this is that in most cases the single biomarker assay cannot show the level of sensitivity and specificity necessary to be an effective diagnostic. 

The examples of this in the market place are several. CA-125 for ovarian cancer and CA15.3 for breast cancer cannot be used as screening tools only as a way of monitoring treatment [8-11]. The PSA test that is used as a screening tool shows sensitivity and specificity of 66%, and thus about one third of the cancers are missed and one third of patients go for unnecessary prostate biopsies. When 

Chart 1. This is a schematic of the way the diagnostic for diabetes functions moving from the cause of the disease to the use of the biomarker glucose. 

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The important messages to remember from this chapter are to think carefully about the discovery experiment first. Put together a solid team with the skills necessary to accomplish the project. Think carefully about the question that is being asked Is it reasonable and achievable Plan the project well and listen to potential problems and challenges so that the question can be answered satisfactorily. Focus on the question being asked and do not get sidetracked until there is an answer to the initial question there is always an opportunity to investigate the data further after the question has been answered. Simplify each step in the biomarker discovery experiment as much as possible so that the data analysis results are as clear as possible. 

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