One of main goals for omics sciences, such as transcriptomics, proteomics and metabolomics, in medicine is biomarker discovery for diagnostics of common non-infectious diseases. The opinion paper discusses diagnostic parameters, which limit the use of the biomarkers, as well as a positive predictive value, and conditions providing possible application of the biomarkers for early diagnostics. Using some examples from proteomics, it is stated that omics technologies, which measure gene expression products, are more often used to discover prognostic and predictive biomarkers. These biomarkers help to classify already diagnosed patients to groups with different disease management.