Quantification of arabinitol in serum by selected ion monitoring as a diagnostic technique in invasive candidiasis

D-Arabinitol was identified by mass spectrometry as a metabolite of Candida albicans and Candida tropicalis. For quantification, serum was deproteinized with acetone, the supernatant was evaporated to dryness, the silyl derivative was formed, and a portion was injected into a combined gas chromatograph-mass spectrometer system. Erythritol or 2-deoxy-galactitol was the internal standard. The protonated molecular ions, obtained in chemical ionization with isobutane, were monitored. For 39 normal subjects the mean endogenous arabinitol concentration was 0.52 μg/ml (standard deviation, ±0.34). An increment of 0.2 μg of arabinitol per ml could be quantified. Of 11 cases with diagnosed invasive candidiasis, 9 had arabinitol levels >1.2 μg/ml (8 μM) in the range of 1.2 to 25.0 μg/ml; the remaining 2 cases had levels in the normal range. Six cases of diagnosed colonized candidiasis showed normal arabinitol levels.