Isobaric tagging approaches in quantitative proteomics: the ups and downs

Isobaric tagging has proven to be a popular quantitative proteomics tool and has been rapidly adopted to study a wide range of biological questions in the few years since its commercialization. While the flexibility and multiplexing capacity afforded by this technology are clear attractions, it is not without its shortcomings. As the speed and sensitivity of mass spectrometers have improved and the application of isobaric tags to all manner of biological systems has increased, significant issues with quantitative accuracy and precision have come to light. Here we review the issues associated with the use of isobaric tagging methods and discuss the possible solutions which have been proposed to improve their precision and accuracy to approach the levels required within quantitative proteomics.