Characteristics of Biomarkers

An important consideration in the use of biomarkers is the practicality of subsequent analysis, which is likely to be far more successful and robust if based on an uncomplicated physiological or biochemical assay that can be carried out with minimal training and preexisting equipment (Figure 2). Nonetheless, the need for specialist techniques or expertise should not exclude a potential biomarker, especially where it contributes to advancing therapies for a serious or unmet medical need. Other practical considerations include the need for assays to be transferrable across international boundaries, supported by low background and variability of the measured parameter coupled with a robust increase or decrease signifying the biological endpoint of interest. Indeed, lower and upper limits for normal values would be better if minimally influenced by age, gender, or race within the human population. Similarly, a biomarker of drug-.nduced toxicity would be better if it were largely unaffected by disease states expected in the patient population of interest or, indeed, any co-medication that might be present or recently administered. However, this is often not the case, and the best that can be expected is some understanding of these relationships to mitigate against difficult or erroneous interpretation. In addition, an ideal biomarker should exhibit

Figure 2 Technical aspects of biomarker utility. Biomarkers must be sufficiently robust biologically and technically to transfer across patient groups and across international boundaries. This is illustrated by the different variables that need to be overcome or accommodated in the assay.

sufficient sensitivity (not too many false negatives) and specificity (not too many false positives) to underpin clinical decisions.

As well as the technical aspects of biomarker assays, there are additional practical considerations to enhance appropriateness and usability. First, a biomarker needs to be accessible and ideally could be noninvasive. If this is not possible, a biomarker could be measurable in blood and other body fluids obtained with minimal additional impact on the subject. If this cannot be achieved, biomarkers may be detectable with increasing impact on the patient via a peripheral or central biopsy. Finally, biomarker research for the advancement of medical knowledge can be conducted after autopsy. Examples of noninvasive methods would include standard physiological measures of cardiovascular parameters such as blood pressure, heart rate, and electrocardiogram, or could be ophthalmological. Fluids could include feces, saliva, and urine, in addition to standard blood sampling. Skin and hair follicles would be examples of peripheral biopsy and muscle and liver needle samples provide the most common route of more invasive biopsy.

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Project Management Made Easy

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