Diagnosis of albuminuria by tryptic digestion and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry.

Background: Matrix-assisted laser desorption ionization/time-of-flight (MALDI-TOF) mass spectrometry has been successfully used to detect trace albumin in urine for the diagnosis of albuminuria. However, only the monomeric form of albumin was detected with this approach.

Methods: Trypsin was used to digest urinary albumin and its related compounds in urine to produce characteristic peptides. The digest solution was subsequently analyzed by MALDI-TOF MS to obtain peptide ion signals which were used as diagnostic biomarkers for albuminuria.

Results: The analytical protocol was optimized for efficient digestion and high-performance MALDI-TOF MS analysis. The limit of detection (LOD) of albumin in urine was about 5×10(-7)M.

Conclusions: Trypsin digestion combined with MALDI-TOF MS analysis is an efficient and simple approach for rapidly diagnosing albuminuria.