Establishment Of Serum Uric Acid Reference System And Clinical Application

Uric acid (UA) is the end metabolism product of purine nucleosides, its determination in serum is a powerful indicator of metabolic alterations or disease appearance. Uric Acid diagnosis hyperuricemia (serum UA levels above 7mg/dL in men and above 6 mg/dL in women), gout, kidney failure, uremia, cardiovascular-related diseases, treatment and prognosis also have great importance. An accuracy base in the form of serum-based materials with known concentrations of UA can provide clinical laborarories with an important component of ensuring that payients’samples are accurately measured. To this end, the need exisit for a method of demonstrated good accuracy and high precision, i. e., a definitive method, for the value assignment of standards. There are lots of determination methods for UA, mainly include voltammetry, capillary electrophoresis, phosphate tungsten reduction, uricase method, uricase-peroxidas coupled reaction, high performance liquid chromatography, and isotope dilution mass spectrometry. We describe our optimization and evaluation of a ultraviolet uricase-method for UA in serum, according to Joint Commission International Laboratory Medicine traceability (JCTLM) serum UA reference method measurement procedures, combined with the enzymatic uric acid as a candidate reference method proposed by American Association for Clinical Chemistry (AACC) in 1973 and UA detection methods Clin Chem magazine published in 1982. To establish candidate reference method of UA, experiment was divided into candidate reference method procedure, method comparison of two parts, optimization methods from multiple angles, promoting the standardization of clinical detection of serum uric acid and harmonization. ObjectiveWe plan to establish ultraviolet uricase method as a reference method forMethodsThe improved reference method for UA was established in accordance with the documents of Clinical and Laboratory Standards Institute (CLSI).we evaluated the accuracy, precision, linearity, recovery, effect of interferences, uncertainty. Fresh serum samples were simultaneously assayed by the candidate reference method, Roche PPI Modular P800 system and VITROS5.1FS system for comparison.ResultsExcellent reproducibility was obtained with within-set coefficient of variations (CVs) less than 0.5%and day CVs less than 2.5%. Linearity was also obtained with upper limit of 1648.9μmol/L. The deviation of RELA-A was 0.2%, RELA-B was -0.8%and SRM909C was -0.1%. The average recoveries of three different spiked concentration samples were 99.6,99.4,102%. Fifteen kinds of uric acid interfering substances were taken into account, the candidate reference method showed the capability of resistance to interference from triglycerides with concentration≤44mmol/L, hemoglobin≤13.6g/L, total bilirubin≤342μmol/L, ascorbic acid≤1.7mmol/L, glucosc≤55mmol/L, creatinine≤5mg/dL, urea≤300mg/dL, xanthine≤527μmol/L, hypoxanthine≤ 869.3μmol/L, adenine≤858μmol/L, allopurinol≤294μmol/L, EDTA≤ 0.34mmol/L, lithium heparin≤62.5U/L, sodium oxalate≤0.5mmol/L. Spectrophotometer, analytical balance, volumetric flasks and pipettes were verified by the laboratory, experiments related factors were assessed, reaching uncertainty requirements. The proposed method has a good correlation compared with X1 and X2, Y=1.0382X1-9.0294, R2=0.9898, Y=1.0022X2+13.236, R2=0.9701.ConclusionThis reference measurement procedure allows values to be assigned to controls and calibrators that are traceable to the primary UA reference material, which demonstrates good accuracy and precision and a low degree of uncertainty, and is free interferences from lots of substances, qualifies as a candidate reference method and can be used as an alternative reference method to provide an accuracy base to which the routine method can be compared.