Diagnostic Biomarkers
A biomarker is considered an objective measure that can reflect what is happening in an organism. They can be measured in different matrices or sample types and would be used as an indication of an existing disease. Biomarkers are crucial for the development of medical therapeutics and they can be broadly used within research and clinical practice. Understanding their applications could result in benefits for patients.
As mentioned by Robert Califf in his 2018 minireview: “Biomarkers are critical to the rational development of medical diagnostics and therapeutics, but significant confusion persists regarding fundamental definitions and concepts involved in their use in research and clinical practice. Clarification of the definitions of different biomarker classes and a better understanding of their appropriate application could yield substantial benefits”. Hence the classification into different groups: diagnostic, monitoring, pharmacodynamic/response, predictive, prognostic, safety, and susceptibility/risk.
Specifically, diagnostic biomarkers are used to detect or confirm a disease or condition in an individual. In the clinics, these biomarkers would be used to identify patients with a specific disease and classify the disease. For the detection of these molecules, accurate and sensitive medical devices and tools are required.
For the detection and measurement of diagnostic biomarkers, it is important to keep in mind the complexity of the molecule that is to be analyzed. Defining the right method for analysis in the most accurate way will result in a reliable, precise, and repeatable measurement. Part of the process requires the validation of the method which will ensure the accuracy of the results supporting the value of the biomarker.
Another aspect to consider would be the validation and inclusion of appropriate standards that would help define the presence or absence of the disease or condition. Standards might be defined by health organizations (international or national). Biomarkers with no defined standards might be complicated to compare among assays and the readouts could be more unpredictable. Hence, the definition of thresholds within the clinics becomes of great use for defining the clinical application of the biomarker.
For biomarker qualification, demonstration of both analytical validation (as it relates to the accurate and precise measurement of the biomarker) and clinical validation (as it relates to the correct interpretation of the biomarker measurement for a specific context of use) are necessary.
As mentioned by Steven P. Piccoli et al in their 2019 publication, “For biomarker qualification, demonstration of both analytical validation (as it relates to the accurate and precise measurement of the biomarker) and clinical validation (as it relates to the correct interpretation of the biomarker measurement for a specific context of use) are necessary”.
Important to keep in mind that analytical validation is the process of establishing that the performance of a test, tool, or instrument is acceptable in terms of its sensitivity, specificity, accuracy, precision, and other relevant performance characteristics using a specified technical protocol, which may include specimen collection, handling, and storage procedures.
