Figure 3.

Various study designs used from salivary metabolomics to saliva-based OC test. The top layer describes the general study designs used to identify and validate diagnostic markers. The middle layer describes case-control and cohort studies. The top layer controls the number of OC and non-OC participants, whereas the middle layer includes a low rate of OC owing to the low prevalence rate in the actual cohort. The bottom layer shows the requirements of the saliva-based OC test. SoP establishment and multi-center-level validations are necessary to discover and validate biomarkers using metabolomics. The development and validation of a cost-effective and high-throughput assay that enables targeted analyses of the biomarker is required for clinical use.