An integrated discovery to targeted proteomics approach was used to investigate the protein profiles of good and non–responders to anti-TNF-alpha and T-cell inhibitor treatments in PsA patients. Reverse phase liquid chromatography coupled to tandem mass spectrometry was used to generate protein profiles of synovial tissue obtained at baseline from 10 PsA patients who then commenced anti-TNF-alpha therapy (adalimumab). Targeted proteomics using multiple reaction monitoring was used to confirm and pre-validate a potential protein biomarker panel in 18 and 7 PsA patient samples respectively.