The most common methods for determination of uric acid in serum are based on the use of the enzyme uricase. Uric acid is enzymatically oxidized by oxygen to produce hydrogen peroxide, allantoin, and carbon dioxide. The four most often applied uricase methods are critically compared in this review.

Uricase based methods for determination of uric acid in serum

A method for the determination of creatinine in human serum by isotope dilution-mass spectrometry is described The analytical procedure comprises the following steps: Addition of [13C,15N2 )creatinine to the serum sample; ion exchange chromatography on the cation exchange resin AG 50W-X2; formation of the trimethylsilyl derivative; gas liquid chromatography-mass spectrometry (GC-MS); selected ion monitoring (SIM) at the m/z-values 329 and 332; calculation of the amount of creatinine in the serum sample from the isotope ratio, as measured by GC-MS [13C,15N2]Creatinine was prepared by chemical synthesis The substance is then used as internal standard for the measurement of creatinine in serum samples The imprecision of the method was in the range from 035 to 105% (coefficient of variation) as determined by repetitive measurements of creatinine in 13 different control sera on different occasions The lower limit of detection of the mass spectrometer in the selected ion monitoring mode is about 05 ng creatinine with a signal to noise ratio of 3:1 The accuracy of the method is achieved by the use of the isotope dilution principle in combination with GC-MS In view of the high specificity and exact control of recovery, the procedure for the measurement of creatinine in human serum, as described here, may be considered as a definitive method in clinical chemistry

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Determination of creatinine in human serum by isotope dilution-mass spectrometry. Definitive methods in clinical chemistry, IV.

This study was designed to establish reference ranges for serum uric acid among healthy adult Assamese population. Samples from 1470 aged 35&#x2013;86 years were used to establish age and sex related reference range by the centile method (central 95 percentile) for serum uric acid level. There were 51&#x25; () males and 49&#x25; () females; 75.9&#x25; () of them were from urban area and the rest 24.1&#x25; () were from the rural area. Majority of the population were nonvegetarian (98.6&#x25;, ) and only 1.4&#x25; () were vegetarian. The mean age, weight, height, and uric acid of the studied group were years, &#x2009;kg, &#x2009;cm, and &#x2009;mg/dL, respectively. There is a statistically significant difference in the mean value of the abovementioned parameters between male and female. The observed reference range of uric acid in the population is 2.6&#x2013;8.2&#x2009;mg/dL which is wider than the current reference range used in the laboratory. Except gender (), we did not find any significant relation of uric acid with other selected factors.

https://downloads.hindawi.com/journals/bri/2014/171053.pdf

Reference Ranges for Serum Uric Acid among Healthy Assamese People

Measurement of uric acid, ascorbic acid, and related metabolites in biological fluids.

Oxidative stress is an imbalance between reactive oxygen species exposure and the ability of organisms to detoxify the reactive intermediates and to repair the oxidative damage of biologically important molecules. Many clinical studies of oxidative stress unfortunately provide conflicting and contradictory results. The ability of antioxidant systems to adequately respond to oxidative stress can be used in laboratory diagnostics. In the present review, methods using the ratio of reduced and oxidized forms of uric acid, ascorbic acid, glutathione and coenzyme Q10 as suitable indicators of oxidative stress are discussed. From the mentioned publications it is evident that suitable sample preparation prior to analysis is crucial.

The ratio of oxidized and reduced forms of selected antioxidants as a possible marker of oxidative stress in humans.

Uric acid as measured in serum by three different uricase (EC 1.7.3.3) methods (aca, Ektachem, and SMAC) and by the SMAC method with phosphotungstic acid was compared with a candidate Reference Method for uric acid. Serum specimens from 83 patients (uric acid concentrations, 19 to 141 mg/L) were analyzed by all five methods. Results were compared by using linear regression analysis, and the mean difference between results by the candidate Reference Method and the four other methods was calculated. Compared with the candidate Reference Method, the aca method gave the smallest deviation from zero for the intercept and the smallest mean difference, and the SMAC phosphotungstic acid method showed a slope closest to unity. The SMAC uricase method had the largest intercept and greatest deviation of the slope from unity.

Four methods for determining uric acid compared with a candidate reference method

We compared the Du Pont aca (phosphotungstate-enzymic cholesterol) and the Dow (dextran sulfate/Mg2+-enzymic cholesterol) methods for the determination of high-density lipoprotein cholesterol (HDLC) and total cholesterol in serum from 113 patients. The aca results for both total cholesterol and HDLC were significantly greater (p less than 0.0001) than the Dow results, the aca method overestimating the HDLC concentration (mean recovery 107.2% in serum samples with values assigned by the Centers for Disease Control). The precision of the aca method for HDLC was essentially the same as that of the Dow method. Bilirubin (up to 0.17 g/L), hemoglobin (up to 4 g/L), and slight lipemia (triglycerides up to 5.4 g/L) did not interfere with the aca method.

R Chesler

Papers

Four methods for determining uric acid compared with a candidate reference method

Comparison of the Du Pont aca and Dow methods for determination of high-density lipoprotein cholesterol.