Cessation of Gout Following Portacaval Shunt

James R. Klinenberg, MD
JAMA. 1968;206(7):1576. doi:10.1001/jama.1968.03150070114035.
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To the Editor:—  Lefkovits et al, "Cessation of Gout Following Portacaval Shunt (205:73, 1968), suggest another method for the determination of urinary oxypurines which is said to be similar in principle but much less tedious than the enzymatic spectrophotometric method which we have previously reported.1In fact, these methods are not similar in principle and it is important that the differences be emphasized. The method described by Irving measures the increase in absorbance at 292 nanometer (nm) accompanying the conversion of hypoxanthine or xanthine to uric acid by xanthine oxidase. However, xanthine has a substantially greater absorbance at 292 nm than does hypoxanthine (Figure); the increase in absorbance at 292 nm accompanying the oxidation of 1.0μM of xanthine per milliliter to uric acid is 9.29 while that for the oxidation of hypoxanthine is 12.33. Therefore by the simplified method described, there is significant error in the measurement of


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