Over the past decade, chemical labeling with isobaric tandem mass tags,
such as isobaric tags for relative and absolute quantification reagents
(iTRAQ) and tandem mass tag (TMT) reagents, has been employed in a wide
range of different clinically orientated serum and plasma proteomics
studies. In this review the scope of these works is presented with
attention to the areas of research, methods employed and performance
limitations. These applications have covered a wide range of diseases,
disorders and infections, and have implemented a variety of different
preparative and mass spectrometric approaches. In contrast to earlier
works, which struggled to quantify more than a few hundred proteins,
increasingly these studies have provided deeper insight into the plasma
proteome extending the numbers of quantified proteins to over a
thousand.