Shinsuke Kimata1, Katsuhiko Mizuguchi2, Shizuo Hattori2, Shinichi Teshima2, Yoshimasa Orita3. 1. Tsuruga Institute of Biotechnology, Toyobo Co. Ltd., 10-24 Toyo-Cho, Tsuruga, Fukui, 914-0047, Japan. shinsuke_kimata@toyobo.jp. 2. Diagnostic System Department, Toyobo Co. Ltd., 2-2-8 Dojima-hama, Kita-ku, Osaka, 530-8230, Japan. 3. Osaka Jikei Research Center, 1-2-8 Miyahara, Yodogawa-ku, Osaka, 532-0003, Japan.
Abstract
BACKGROUND: Inulin clearance (Cin) is widely considered to be a gold-standard assessment of glomerular filtration rate (GFR). Although inulin concentrations are commonly determined by the anthrone method, this method has several disadvantages, including a hazardous heating procedure using a strong acid, as well as a nonspecific reaction and being influenced by other saccharides such as glucose. METHOD: Here, we report the development of a new automated, enzymatic inulin assay. This method uses D: -fructose dehydrogenase (EC1.1.99.11), which does not require NAD or NADP as the electron acceptor, and utilizes oxygen transfer from hydrogen peroxide to an electron acceptor in a sensitive chromophoric system. This method allows rapid and accurate determination of inulin concentrations, and takes only 15 min on automated analyzers. We evaluated this new assay and compared it with the anthrone method. RESULTS: The detection limit value and linearity of the new method were 5 mg/l and up to 300 mg/l, respectively. The within-run precision coefficient of variations (CVs) for serum and for urine were 2.05 +/- 0.79% (mean +/- SEM; n = 3) and 0.92 +/- 0.24%, respectively, and the between-run precision CVs for serum and for urine were 1.91 +/- 0.72% and 1.86 +/- 0.17%, respectively. No influence of glucose was observed with the new method, while a positive influence of 38.7% was observed with the anthrone method. However, neither method was influenced by fructose (3.0 mg/l in serum or 30 mg/l in urine). The analytical recovery rates of inulin were 97.8 +/- 0.7% (mean +/- SEM; n = 6) in serum and 99.0 +/- 0.4% in urine using the enzymatic method. We compared results for the enzymatic method and the anthrone method using 46 serum samples and 46 urine samples. Bland-Altman plots showed no significant difference between the two methods for the serum samples. However, inulin recovery in the urine samples measured by the enzymatic method was about 5% higher than that obtained by the anthrone method. CONCLUSION: The new enzymatic assay offers a more convenient and more accurate measurement of inulin and may be suitable for routine procedures by automated analyzers in clinical laboratories.
BACKGROUND: Inulin clearance (Cin) is widely considered to be a gold-standard assessment of glomerular filtration rate (GFR). Although inulin concentrations are commonly determined by the anthrone method, this method has several disadvantages, including a hazardous heating procedure using a strong acid, as well as a nonspecific reaction and being influenced by other saccharides such as glucose. METHOD: Here, we report the development of a new automated, enzymatic inulin assay. This method uses D: -fructose dehydrogenase (EC1.1.99.11), which does not require NAD or NADP as the electron acceptor, and utilizes oxygen transfer from hydrogen peroxide to an electron acceptor in a sensitive chromophoric system. This method allows rapid and accurate determination of inulin concentrations, and takes only 15 min on automated analyzers. We evaluated this new assay and compared it with the anthrone method. RESULTS: The detection limit value and linearity of the new method were 5 mg/l and up to 300 mg/l, respectively. The within-run precision coefficient of variations (CVs) for serum and for urine were 2.05 +/- 0.79% (mean +/- SEM; n = 3) and 0.92 +/- 0.24%, respectively, and the between-run precision CVs for serum and for urine were 1.91 +/- 0.72% and 1.86 +/- 0.17%, respectively. No influence of glucose was observed with the new method, while a positive influence of 38.7% was observed with the anthrone method. However, neither method was influenced by fructose (3.0 mg/l in serum or 30 mg/l in urine). The analytical recovery rates of inulin were 97.8 +/- 0.7% (mean +/- SEM; n = 6) in serum and 99.0 +/- 0.4% in urine using the enzymatic method. We compared results for the enzymatic method and the anthrone method using 46 serum samples and 46 urine samples. Bland-Altman plots showed no significant difference between the two methods for the serum samples. However, inulin recovery in the urine samples measured by the enzymatic method was about 5% higher than that obtained by the anthrone method. CONCLUSION: The new enzymatic assay offers a more convenient and more accurate measurement of inulin and may be suitable for routine procedures by automated analyzers in clinical laboratories.
Authors: O Sugita; Y Tomiyama; T Matsuto; M Okada; F Gejyo; M Arakawa; S Takahashi; Y Watazu; N Kaneda Journal: Ann Clin Biochem Date: 1995-11 Impact factor: 2.057
Authors: Andrew S Levey; Kai-Uwe Eckardt; Yusuke Tsukamoto; Adeera Levin; Josef Coresh; Jerome Rossert; Dick De Zeeuw; Thomas H Hostetter; Norbert Lameire; Garabed Eknoyan Journal: Kidney Int Date: 2005-06 Impact factor: 10.612