Selected/multiple reaction monitoring-mass spectrometry (SRM/MRM) is an analytical method that is frequently combined to the use of stable isotope-labeled standard (SIS) peptides for absolute protein quantification. The application of SRM/MRM is a relatively recent development in the proteomics field for analysis of biological samples (plasma, urine, cell/tissue lysates) targeting to a large extent biomarker validation. Although MRM generally by-passes the use of antibodies (being linked to sub-optimal assay specificity in many cases), bioanalytical validation of MRM protocols has not been robustly applied because of sensitivity issues, in contrary to antibody-based methods. In this chapter, we will discuss the points that should be addressed for MRM method development in clinical proteomics applications.
