What Is Serum Uric Acid?

(1) Phosphotungstic acid reduction method: 150-420 mol / L for males; 90-357 mol / L for females. (2) Uricase-peroxidase coupling method: 90-420 mol / L for adults.

Uric acid is the final product of purine catabolism. Excreted by the kidneys with urine. The content of uric acid in healthy adults is about 1.1g, about 15% of which is in the blood. After filtering through the glomerulus, most of the uric acid in the blood is reabsorbed by the renal tubules. Uric acid is one of the important components of non-protein nitrogen in the plasma. In severe kidney damage, the blood uric acid can be significantly increased. It does not change much when slightly damaged. Therefore, the determination of serum uric acid is a sensitive indicator for the diagnosis of severe renal impairment.

Name: Serum uric acid

category: Renal function

Normal serum uric acid

(1) Phosphotungstic acid reduction method: 150-420 mol / L for males; 90-357 mol / L for females. (2) Uricase-peroxidase coupling method: 90-420 mol / L for adults.

Clinical significance of serum uric acid

(1) Increased serum uric acid: Serum uric acid is significantly increased in acute and chronic nephritis, and it is more significant than BUN and Cr, and it appears earlier. Other renal diseases, such as renal tuberculosis, pyelonephritis, hydronephrosis and other blood uric acid are also increased. Because of the greater influence of extrarenal factors, the increase is not directly proportional to the degree of impaired renal function. Gout, caused by disturbance of nucleoprotein and purine metabolism, blood uric acid> 595 mol / L. Leukemia, multiple myeloma, polycythemia vera, etc. increase blood uric acid due to increased nucleic acid metabolism. Others: chloroform, carbon tetrachloride, lead poisoning, eclampsia, pregnancy reaction, strenuous exercise, etc. (2) Decreased serum uric acid: Rarely seen in malignant anemia and celiac disease.

Serum uric acid precautions

(1) Phosphotungstic acid reduction method: To ensure accurate and reliable test results, each measurement should include quality control serum, and the obtained value must be within the allowable range. The OCV recommended by the WHO is ± 5%, and the RCV is ± 10%. The RCV recommended by China is 7.5%. Red blood cells contain many non-specific reducing substances, so serum or plasma is used as a sample. Potassium oxalate reacts with phosphotungstic acid to form insoluble potassium phosphotungstate, which can cause turbidity of the color developing solution. Therefore, potassium oxalate cannot be used as an anticoagulant. Serum and urine uric acid is stable for 3 days at room temperature. Refrigerated urine can cause precipitation of urate. The solution is: adjust the pH of the urine to 7.5-8.0, and heat it to 50 ° C to completely dissolve the precipitate, and then measure it again. The solubility of uric acid in water is extremely low. When preparing the standard solution, add lithium carbonate to heat the solution. If there is no lithium carbonate, potassium carbonate or sodium carbonate can be used instead. When protein is precipitated with tungstic acid, part of the uric acid can be precipitated together with the protein, and the amount of precipitation varies with the pH value of the filtrate. Such as the filtrate pH <3, the recovery rate of uric acid is less than 90%, pH value is 3.0-4.3, recovery rate is 93% -103%; pH value is 2.4-2.7, recovery rate is 74% -97%. The quality of sodium tungstate should be guaranteed. If it contains molybdenum, it can react with phenols in the blood and affect the measurement results. The colorimetric time should be strictly controlled, and the colorimetric effect is best within 20-30min at room temperature. (2) Uricase-peroxidase coupling method: To ensure satisfactory quality, quality control serum should be measured at the same time for each measurement, and the value obtained should be within the allowable range. The accuracy of the standard solution and the accuracy of the amount of sample taken have a great influence on the measurement results. If the results tend to be high or low, the reason should be found from the standard solution and the amount of standard taken. The glass equipment used should be clean and dry, and the accuracy of the pipette should be high. The dry powder reagent is stored at 2-6 ° C and is stable for at least 6 months. The reconstituted reagent can be used for 6-8h at room temperature; it can be stable for 12-24h at 2-6 ° C. If the dry powder is found to be damp and agglomerated, or the color appears, and the reconstitution does not match the measured value of the fixed serum, it means that the reagent Deterioration should be discarded. The final color reaction is a Trinder reaction, so it is greatly affected by the redox agent. When the reducing agent is contaminated, the result is significantly reduced or no color is developed. Contamination of the oxidant can result in high results or turn reagents red.