High-resolution mass spectrometry measurement of N-terminal carbamylated hemoglobin as a potential marker for chronic diseases with elevated blood urea levels.

INTRODUCTION: N-terminal carbamylated hemoglobin (CarHb) reflects long-term blood urea levels and has potential as a marker for chronic kidney disease (CKD) and other chronic conditions with elevated blood urea levels. A liquid chromatography-high-resolution mass spectrometry (LC-HR-MS) method was developed to measure CarHb. METHODS: Apparent CarHb/Hb ratios were calculated from the peak area ratios of carbamylated to native N-terminal peptides digested from hemoglobin alpha and beta subunits. Blood samples from healthy individuals, CKD patients, and chronic obstructive pulmonary disease (COPD) patients were analyzed. RESULTS: The apparent CarHb/Hb ratios were significantly higher in CKD and COPD patients compared to healthy individuals. However, no significant differences were observed between the CKD and COPD patient groups. CONCLUSIONS: In this study, an LC-HR-MS method was developed for quantifying the apparent CarHb/Hb ratios and exploring their potential for clinical diagnostic applications. CarHb is a promising marker for monitoring kidney diseases and other chronic conditions with elevated blood urea levels. Beyond CarHb, the use of other carbamylated proteins as clinical diagnostic and prognostic markers can be explored.