Relative quantification of albumin and fibrinogen modifications by liquid chromatography tandem mass spectrometry in the diagnosis and monitoring of acute pancreatitis

• Sensitive detection of protein products of high abundance compared to enzymes.
• Simple relative quantification approach without the need for internal standardisation.
• Defined reference range for modified protein proportions.
• Proteins with different degradation kinetics offer tracking and disease grading option.
• Refined, robust LC–MS/MS method for measurement of a prospectively large analyte menu.

The increasing availability of liquid chromatography tandem mass spectrometry (LC–MS/MS) in clinical laboratories provides the opportunity to replace or complement present underperforming immuno- and chemometric assays. Amylase and lipase show limited specificity and sensitivity for pancreatic inflammation and lack the capacity of monitoring the disease due to their short half-lives. Previous findings suggested that cleavage products of the pancreatic enzyme carboxypeptidase A could be a more suitable indicator for defining and classifying pancreatic inflammation. The plasma proteins albumin and β-fibrinogen were digested with trypsin and truncated forms (des-Leu-albumin, and des-Gln-β-fibrinogen) quantified against their non-truncated forms by LC–MS/MS. Four hundred fifty eight samples from 83 patients were used to evaluate the novel method and affirm its suitability for detecting acute pancreatitis. A robust, selective, precise and accurate LC–MS/MS method was set up to measure the proportion of truncated proteins. Reference ranges for the proportion of the truncated albumin and β-fibrinogen were from 2% to 9% and 3% to 25%, respectively. Acute pancreatitis patients had values above these ranges and were distinctly separated from reference control individuals. The longer circulating half-lives of albumin and fibrinogen compared to pancreatic enzymes themselves provide the potential to diagnose pancreatitis more specifically over a longer time period, to monitor the course of the disease, and to track recurrent complications. The wide range of the proportion and the differential half-life of both truncated proteins could also be used for assessing the severity of pancreatitis.