Considerations on selected reaction monitoring experiments: implications for the selectivity and accuracy of measurements.

Targeted MS analyses based on selected reaction monitoring (SRM) has enabled significant achievements in proteomic quantification, such that its application to clinical studies has augured great advancements for life sciences. The approach has been challenged by the complexity of clinical samples that affects the selectivity of measurements, in many cases limiting analytical performances to a larger extent than expected. This Personal Perspective discusses some insight to better comprehend the mismatch between the often underestimated sample complexity and the selectivity of SRM measurements performed on a triple quadrupole instrument. The implications for the design and evaluation of SRM assays are discussed and illustrated with selected examples, providing a baseline for a more critical use of the technique in the context of clinical samples and to evaluate alternative methods.