A "biomarker" (biological marker) is an indicator of a bodily function that can be objectively measured. A wide range of possible biomarkers for IBS have been considered but at the present only gut, transit measured using radio-isotope markers meet the criteria of reproducibility and availability. While barostat studies perform reasonably in expert centers, to do them reproducibly requires considerable effort and standardization. This makes them unsuitable for widespread use. However radio-isotope tests are expensive and of limited availability so the search for other more convenient markers including blood and stool tests is still an important goal for the future.
Biomarkers for precision medicine are part of a potentially new set of clinical tools. In the case of metastatic colorectal cancer (mCRC), only two predictive biomarkers have so far been identified and clinically. In this case, the lack of data beyond retrospective studies and successful approaching biomarkers has been the main cause of severe clinical need for clinical trials.
The field of biomarker research is also expanding to include a combinatorial approach to multi-omic sources. The combination of groups of biomarkers from different omic data makes it possible to develop panels that respond to the treatment of multiple biomarkers at the same time. One such area is the multi-omic biomarkers in the research expansion of mitochondrial DNA. Mitochondrial DNA mutations have been shown to correlate with risk, progression, and response to treatment of squamous cell carcinoma in the head and neck. In this example, a relatively low-cost sequencing pipeline has been shown to be capable of detecting low-frequency mutations in tumor-associated cells. These highlights the general snapshot capacity of mitochondrial DNA-based biomarkers to capture heterogeneity among individuals.