Cost-effective modification of the Hypronosticon procedure for urinary hydroxyproline.

Our modification for one resin tabletper urine is cost-effective forsmallorlargebatchanalyses. The hydrolysis of each urine isdone in singleton. The inhibitory effects of ascorbic acid on enzymatic cholesterol determinations and other peroxidase reactions are well documented (1). Recently, we experienced a total inhibition of the cholesterol assay in the Olympus Demand. The reagents for this assay are obtained from Cooper Biomedi-cal. We obtained a serum cholesterol value of 0 mmoIJL for an inpatient at our hospital on his first day of admission, and this led us to investigate the reason for this obviously inaccurate result. The cholesterol value for this specimen with use of Liebermann-Burchard reagent was 2.9 mmolJL and the ascorbic acid concentration was 9255 imoIJL (normal 30 to 110 tmoI/L). The patientwas a 71-year-oldman with pancreatic cancer who had been losing weightforsome time, and because of this and his decreased appetite had been taking many vitamins and food supplements. Three days after admission the cholesterol value obtained in the Olympus Demand was 2.9mmoLIL (3.0mmol/L by Lieber-mann-Burchard) and the ascorbic acid concentration was 113 .tmo1/L. To samples from a serum pool with a cholesterol value of 4.9 mmol/L we added a constant volume of freshly prepared ascorbic acid solutionsto give final concentrations of 100 to 6000 pmol/L. These specimens were then assayed in duplicate in the Demand and in the TDx. An interferogram as described by Glick et al. (2) of the effect of ascorbic acid on the cholesterol assay for the Demand and for the TDx is shown in Figure 1.