Results of the LC-MS/MS method comparison with Access™ analyzer (Beckman Coulter) using Tg-AAb negative (A, B) and Tg-AAb positive samples (C). A: concentrations 0–350 ng/mL IA=0.99*LC-MS/MS-3.1, r=0.980, Sy,x=14.8; B: concentrations <60 ng/mL. IA=0.94*LC-MS/MS-3.7, r=0.946, Sy,x=4.2; C: IA=0.53*LC-MS/MS −0.1, r=0.586, Sy,x = 1.1.