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Abstract: A patented kinetic uricase method was evaluated for serum uric acid assay. Initial absorbance of the reaction mixture before uricase action (A₀) was obtained by correcting the absorbance at 293 nm measured before the addition of uricase solution, and background absorbance (A_b) was predicted by an integrated method. Uric acid concentration in reaction solution was calculated from ∆A, the difference between A₀ and A_b, using the absorptivity preset for uric acid. This kinetic uricase method exhibited CV<4.3% and recovery of 100%. Lipids, bilirubin, hemoglobin, ascorbic acid, reduced glutathione and xanthine <0.32 mmol/L in serum had no significant effects. ∆A linearly responded to 1.2 to 37.5 μmol/L uric acid in reaction solution containing 15 μl serum. The slope of linear response was consistent with the absorptivity preset for uric acid while the intercept was consistent with that for serum alone. Uric acid concentrations in clinic sera by different uricase methods positively correlated to each other. By bland-Altman analysis, this kinetic uricase method accorded with that by quantifying the total change of UV absorbance on the completion of uricase reaction. These results demonstrated that this kinetic uricase method is reliable for serum uric acid assay with enhanced resistance to both xanthine and other common errors, wider range of linear response and much lower cost.

[1] Aoki, Y., Ihara, H., Nakamura, H., Aoki, T., Yoshlda, M., 1992. Effects of serum bilirubin on determination of uric acid by the uricase-peroxidase coupled reaction. Clin. Chem., 38(7):1350-1352.

[2] Bartl, K., Brandhuber, M., Ziegenhorn, J., 1979. Improved automated kinetic determination of uric acid in serum by use of uricase/catalase/aldehyde dehydrogenase. Clin. Chem., 25(4):619-621.

[3] Bland, J.M., Altman, D.G., 1995. Comparing methods of measurement: why plotting difference against standard method is misleading. The Lancet, 346(8982):1085-1087.

[4] Duncan, P.H., Gochman, N., Cooper, T., Smith, E., Bayse, D., 1982. A candidate reference method for uric acid in serum. I. Optimization and evaluation. Clin. Chem., 28(2):284-290.

[5] Hamilton, S.D., Pardue, H.L., 1982. Kinetic method having a linear range for substrate concentration that exceeds Michaelis-Menten constant. Clin. Chem., 28(12):2359-2365.

[6] Hande, K.R., Perini, F., Putterman, G., Eln, R., 1979. Hyperxanthinemia interferes with serum uric acid determinations by the uricase method. Clin. Chem., 25(8):1492-1494.

[7] Kroll, M.H., Elin, R.J., 1994. Interference with clinical laboratory analysis. Clin. Chem., 40(11):1996-2005 [Erratum appeared in Clin. Chem., 1995, 41(5):770].

[8] Liao, F., 2005. The Method for Enzymatic Analysis of Uric Acid in Body Fluids by Predicting the Background Absorbance. China Patent: ZL 03135649.4. 2005-08-31.

[9] Liao, F., Liu, W.L., Zhou, Q.X., Zeng, Z.C., Zuo, Y.P., 2001. Assay of serum arylesterase activity by fitting reaction curve to an integrated rate equation. Clin. Chim. Acta, 314(1-2):67-76.

[10] Liao, F., Tian, K.C., Yang, X., Zhou, Q.X., Zeng, Z.C., Zuo, Y.P., 2003a. Kinetic substrate quantification by fitting the enzyme reaction curve to the integrated Michaelis-Menten equation. Anal. Bioanal. Chem., 375(6):756-762.

[11] Liao, F., Li, J.C., Kang, G.F., Zeng, Z.C., Zuo, Y.P., 2003b. Measurement of mouse liver glutathione S-transferase activity by the integrated method. J. Med. Coll. PLA, 18(5):295-300.

[12] Liao, F., Zhu, X.Y., Wang, Y.M., Zuo, Y.P., 2005a. The comparison of the estimation of enzyme kinetic parameters by fitting reaction curve to the integrated Michaelis-Menten rate equations of different predictor variables. J. Biochem. Biophys. Methods, 62(1):13-24.

[13] Liao, F., Zhao, Y.S., Zhao, L.N., Tao, J., Zhu, X.Y., Wang, Y.M., Zuo, Y.P., 2005b. Kinetic method for enzymatic analysis by predicting background using uricase as model. J. Med. Coll. PLA, 20(6):338-344.

[14] Sanders, G.T., Pasman, A.J., Hoek, F.J., 1980. Determination of uric acid with uricase and peroxidase. Clin. Chim. Acta, 101(2-3):299-303.

[15] Spain, M.A., Wu, A.H., 1986. Bilirubin interference with determination of uric acid, cholesterol, and triglycerides in commercial peroxidase-coupled assays, and the effect of ferrocyanide. Clin. Chem., 32(3):518-521.

[16] Zhao, L.N., Liao, F., Zhao, Y.S., 2005. Characterization of the inhibition of xanthine on uricase by a linear kinetic method. J. Fourth Mil. Med. Univ., 26(15):1363-1365 (in Chinese).

[17] Zhao, Y.S., Zhao, L.N., Yang, G.Q., Tao, J., Bu, Y.Q., Liao, F., 2006. The characterization of the extracellular uricase from Bacillus fastidious and its application to direct kinetic assay of serum uric acid. J. Huazhong Univ. Sci. Tech. Med. Ed., 35 (in press) (in Chinese).