1. Uric Acid Mr. Mohammed O. Jaber, MLS

2. Uric Acid  Uric acid is formed from the breakdown of nucleic acids and is an end product of purine metabolism.  Uric acid is transported by the plasma from the liver to the kidney, where it is filtered and where about 70% is excreted in Urine.  The remainder of uric acid is excreted into the GI tract.

3. Clinical Significance  Disease states with increased plasma uric acid  Gout  Increased catabolism of nucleic acids  And renal disease  In Gout increased serum levels of uric acid lead to formation of monosodium urate crystals around the joints.  Uric acid test is useful to assess for gout and to monitor patients with renal failure

4. Clinical Significance  To monitor if uric acid levels are too high after chemotherapy or radiation.  Hypouricemia is seldom observed and associated with rare hereditary metabolic disorders.(e.g. Wilson’s disease, Fanconi’s Syndrome)

5. Specimen  Serum or plasma may be used  Stability in serum / plasma:  6 months at -20°C  7 days at 4-8°C  3 days at 20-25°C

6. ANALYTIC METHODS—URIC ACID  Chemical Method (old) :  Phosphotungstic Acid, read the absorbance(Ab) at 700nm (UV). blue Colored product  Enzymatic Method: is More specific  By using Couple reaction of uricase and Peroxidase. Pink solution (Ab at 500nm spectrophotometric) Pink color solution.

7. Enzymatic Colorimetric Principle  Uricase oxidizes uric acid to allantoin and hydrogen peroxide. The hydrogen peroxide formed further reacts with a phenolic compound and 4 aminoantipyrine by the catalytic action of peroxidase to form a Pink coloured quinoneimine dye complex. Intensity of the colour formed is directly proportional to the amount of uric acid present in the sample. Aminophenazone + DHBS

8. Normal Rang  Female: 2.6 - 6.0 mg/dL  Male: 3.5-7.2 mg/dL