SERUM XYLOSE ANALYSIS BY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

A gas chromatography/mass spectrometric (GC/MS) isotope dilution assay for xylose was developed using tertbutyldimethylsilyl-derivatized xyl ose and [C-13](1) xylose, and applied to human serum samples. A calibr ation curve in serum using this assay showed <3% variation (<10 mg/L) for any given point. The correlation coefficient for xylose measuremen ts made on 27 sera between a colorimetric method performed by a nation al commercial reference laboratory and the GC/MS method developed here was .952. However, xylose determinations of 10 of 27 samples differed by >10% (up to 150 mg/L) when colorimetric values were compared to GC /MS. Two of these samples had borderline-low xylose values by GC/MS, b ut were well within the normal range by colorimetric analysis. gas chr omatography/mass spectrometric isotope dilution assay appears to be an accurate method to measure xylose in serum. These data also suggest t hat further prospective studies comparing GC/MS to colorimetric method s are indicated for subjects undergoing oral xylose testing.