Quantitative Profiling of Platelet-Rich Plasma Indole Markers by Direct-Matrix Derivatization Combined with LC-MS/MS in Patients with Neuroendocrine Tumors

Currently, several indole markers are measured separately to support diagnosis and follow-up of patients with neuroendocrine tumors (NETs). We have developed a sensitive mass spectrometry method that simultaneously quantifies all relevant tryptophan-related indoles (tryptophan, 5-hydroxytryptophan, serotonin, 5-hydroxyindoleacetic acid) in platelet-rich plasma. Direct-matrix derivatization was used to make the chemical properties of the indoles...