A mass-spectroscopic method for measuring des-Leu albumin — A novel marker for chronic pancreatitis

Abstract

ObjectivesChronic pancreatitis is a progressive inflammatory disease leading to pancreatic insufficiency. The diagnosis of chronic pancreatitis is challenging, especially in early disease and the current tests have low sensitivity, may be invasive or have limited availability. We previously identified a truncated form of albumin lacking the C-terminal leucine, des-Leu albumin, which was present at high concentration in pancreatitis. We have developed a liquid-chromatography tandem-mass spectrometry (LC–MS/MS) method for measuring this peptide and make some preliminary observations on patient samples. MethodsSerum samples from patients with established pancreatitis and controls were obtained. Diluted serum samples or prepared standards were digested with trypsin. Aliquots of the digest were separated on a reversed-phase column using water:acetonitrile:formic acid mobile-phase with tandem-mass spectrometry detection. Percentage composition of des-Leu albumin was determined from a response curve. ResultsThe C-terminal peptide, LVAASQAALG- of des-Leu albumin was identified by m/z 901→725, wild type albumin by m/z 1014→825. Additional fragments were monitored as internal reference for digestion and sample integrity. Inter-assay imprecision was estimated at 10%. The percentage composition of des-Leu albumin segregated with the diagnosis of established pancreatitis with median levels of des-Leu albumin of 68% in patients compared to 5% in controls. ConclusionsDes-Leu albumin is a promising novel biomarker for chronic pancreatitis. It allowed clear discrimination of patients with pancreatitis from controls and its long half-life may facilitate monitoring of disease activity. The method described could readily be undertaken in modern clinical chemistry laboratories and will form the basis for further study.