Positive interference of icodextrin metabolites in some enzymatic glucose methods.

earity was apparent between 0.15 and 10 ␮mol/L (r ϭ 0.99). The recovery was 101% Ϯ 10%. Because serum ubiquinone-10 values in our sample pediatric population did not follow a gaussian distribution (assessed by the Kol-mogorov–Smirnov test), we calculated the median and the 2.5 and 97.5 percentiles for reference values. The ubiquinone concentration was independent of sex (P Ͼ0.05, Mann– Whitney test) but decreased significantly with age (r ϭ Ϫ0.383, n ϭ 102, P Ͻ0.0001 for ubiquinone in ␮mol/L; r ϭ Ϫ0.384, n ϭ 102, P Ͻ0.0005 for ubiquinone in ␮mol/mol cholesterol), whereas cholesterol values did not change with age. Ubiquinone concentrations correlated with cholesterol concentrations (r ϭ 0.485, P Ͻ0.00001, Spearman test). After applying statistical analysis to all age groups (Kruskal–Wallis), we established two groups whose ubiquinone concentrations (in ␮mol/L and ␮mol/mol cholesterol) were the most significantly different from one and 169 ␮mol/mol cholesterol (interval , 111–248 ␮mol/mol cholesterol)]. HPLC with UV detection is a rapid and useful procedure for the quanti-fication of total ubiquinone and correlates well with other procedures (5). We established reference intervals for serum ubiquinone in a Med-iterranean pediatric population, showing a decrease of ubiquinone related to age, as was also reported by other authors in several tissues (1). Dietetic habits may influence serum ubiquinone-10 concentrations (6). Therefore, little difference in serum ubiquinone-10 values would be expected between several populations. In our experience, both ubiqui-none-10 and ubiquinone-9 are present in substantial amounts in serum (data not shown). Ubiquinone-9 is not synthesized by humans; however , small amounts have been found in serum by some authors (7) but not by others (2). Interestingly, vegetable oils are the richest sources of ubiqui-none-9 (6), an important food in Mediterranean area. Consequently, ubiquinone-9 is not suitable for use as internal calibrator to assay serum ubiquinone-10, at least in our population ; we, therefore, chose ubiqui-none-7. Serum ubiquinone results are usually reported as molar concentrations but rarely are related to cholesterol (8). The reference intervals thus obtained are different, and the ubiqui-none-to-cholesterol ratio yields a more adjusted reference interval. Moreover, ubiquinone-10 in serum protects lipoproteins from peroxida-tion. Therefore, the relationship between ubiquinone and cholesterol concentrations seems the best means of assessing its biological function in blood. serum and muscle of 5 patients with Kearns-Sayre syndrome and 12 patients with ophthal-moplegia plus. A. Monitoring of ubiquinol-10, ubiquinone-10, carotenoids, and tocopherols in neonatal plasma microsamples using high-performance liquid chromatography with coulometric electrochemical …