Fig. 3. Method comparison of ID-UPLC-MS/MS and the Cobas 8000 ECLIA. (A) Passing–Bablok regression scatter plot. (B) Percent bias plot. The correlation was good (R=0.995, slope=1.564) in 138 random individuals with C-peptide concentrations of 0.55–12.54 ng/mL, but positive percent bias was observed for all concentrations.
Abbreviations: ID-UPLC-MS/MS, isotope dilution-ultraperformance liquid chromatography-tandem mass spectrometry; ECLIA, electrochemiluminescence immunoassay.

Ann Lab Med 2025;45:62~69 https://doi.org/10.3343/alm.2024.0072