Abstract\nBackground: Diabetes testing using saliva, rather than blood and urine, could facilitate diabetes screening in public\nspaces. We previously identified 1,5-anhydro-D-glucitol (1,5-AG) in saliva as a diabetes biomarker. The Glycomarkââ??¢\nassay kit is FDA approved for 1,5-AG measurement in blood. Here we evaluated its applicability for 1,5-AG quantification\nin saliva.\nMethods: Using pooled saliva samples, we validated Glycomarkââ??¢ assay use with a RX Daytona+ clinical chemistry\nanalyser. We then used this set-up to analyse 82 paired blood and saliva samples from a diabetes caseââ?¬â??control study,\nfor which broad mass spectrometry-based characterization of the blood and saliva metabolome was also available.\nOsmolality was measured to account for potential variability in saliva samples.\nResults: The technical variability of the read-outs for the pooled saliva samples (CV = 2.05 %) was comparable to that\nobtained with manufacturer-provided blood surrogate quality controls (CV = 1.38ââ?¬â??1.8 %). We found a high correlation\nbetween Glycomark assay and mass spectrometry measurements of serum 1,5-AG (r2 = 0.902), showing reproducibility\nof the non-targeted metabolomics results. The significant correlation between the osmolality measurements performed\nat two independent platforms with the time interval of 2 years (r2 = 0.887), also indicates the sample integrity.\nThe assay read-out for saliva was not correlated with the mass spectrometry-based 1,5-AG saliva measurements.\nComparison with the full saliva metabolome revealed a high correlation of the saliva assay read-outs with galactose.\nConclusions: Glycomarkââ??¢ assay read-outs for saliva were stable and replicable. However, the signal was dominated\nby galactose, which is biochemically similar to 1,5-AG and absent in blood. Adapting the 1,5-AG kit for saliva analysis\nwill require enzymatic depletion of galactose. This should be feasible, since the assay already includes a similar step for\nglucose depletion from blood samples.
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