Using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry to rapidly screen for albuminuria.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is used as an alternative method for the rapid diagnosis of albuminuria. This technique requires no further sample pretreatment than simply mixing the urine sample with a MALDI matrix and drying under ambient conditions. The resulting MALDI mass spectra reveal albumin ions having charges ranging from +1 to +5. The detection of albumin is possible using any of the three most common MALDI matrices - sinapinic acid (SA), 2,5-dihydroxybenzoic acid (2,5-DHB), or 4-hydroxy-alpha-cyanocinnamic acid (alpha-CHC). Using this analytical approach, the limit of detection for albumin in urine is 10(-6) M, approximately 5 to 10 times lower than that detectable through conventional chemical testing.