A rapid enzymatic fluorometric assay for measuring
D-arabinitol in serum was developed using recombinant
D-arabinitol dehydrogenase from Candida albicans (rArDH). rArDH was produced in Escherichia coli and purified by
dye-
ligand affinity chromatography. rArDH was highly specific for
D-arabinitol, cross-reacting only with
xylitol (4.9%) among all polyols tested. A Cobas Fara II centrifugal autoanalyzer (Roche) was used to measure
NADH fluorometrically when rArDH and
NAD were added to serum extracts, and
D-arabinitol concentrations were calculated from standard curves derived from pooled human serum containing known amounts of
D-arabinitol. The method was precise (mean intra-assay coefficients of variation [CVs], 0.8%, and mean interassay CVs, 1.6%) and rapid (3.5 min per assay) and showed excellent recovery of added
D-arabinitol in serum (mean recovery rate, 101%). The mean and median
D-arabinitol/
creatinine ratios were 2.74 and 2.23 microM/mg/dl, respectively, for the 11 patients with
candidemia compared to 1.14 and 1.23 microM/mg/dl, respectively, for 10 healthy controls (P < 0.01). These results confirm earlier studies showing that serum
D-arabinitol measurement may help to promptly diagnose
invasive candidiasis. The technique shows a significant improvement in terms of accuracy, cost, simplicity, specificity, and speed compared with gas chromatography, mass spectrometry, and earlier enzymatic assays.