URIC ACIDUric acid (or urate) is an organic compound of carbon, nitrogen, oxygen and

hydrogen with the formula C5H4N4O3.

Sources

Uric acid is a chemical created when the body breaks down substances called purines. Purines are found in some foods and drinks, such as liver, dried beans and peas, beer, and wine scallops, game meats, and gravy.

A moderate amount of purine is also contained in beef, pork, poultry, fish and seafood, cauliflower, spinach, mushrooms, green peas, wheat.

In many instances, people have elevated uric acid levels for hereditary reasons.

Excretion

Most uric acid dissolves in blood and travels to the kidneys, where it passes out in urine.

Normal values:

In human blood, uric acid concentrations between 3.6 mg/dL (~214µmol/L) and 8.3 mg/dL (~494µmol/L) (1mg/dL=59.48 µmol/L) are considered normal

HIGH URIC ACID

HYPERURICEMIA: It is classified as:Primary hyperuricemia : Occurs due to inborn error of metabolism.Secondary hyperuricemia : Occurs due to secondary causes e.g cancers etc.

PRIMARY: Gout Lesch-Nyhan syndrome Xanthinuria Adenosine deaminase deficiency

SECONDARY: Due to cancers Renal failure Lead poisoning

1. Gout:

Excess serum accumulation of uric acid can lead to a type of arthritis known as gout.

2. Lesch-Nyhan syndrome:

Lesch-Nyhan syndrome is also associated with very high serum uric acid levels due to lack of enzyme hupoxanthine-guanine phosphoribosyl transferase(HGPRTase)

Spasticity, involuntary movement and cognitive retardation as well as manifestations of gout are seen in cases of this syndrome.

3. Xanthinuria:

Autosomal recessive disease in which large amount of xanthine are excreted in urine

4. Cardiovascular disease:

Although uric acid can act as an antioxidant, excess serum accumulation is often associated with cardiovascular disease.

5. Metabolic syndrome:

Hyperuricemia is associated with components of metabolic syndrome and it has been debated for a while to be a component of it. It has been shown in a recent study that fructose-induced hyperuricemia may play a pathogenic role in the metabolic syndrome.

This agrees with the increased consumption of fructose-base drinks in recent decades and the epidemic of diabetes and obesity.

Greater-than-normal levels of uric acid (hyperuricemia) may also be due to:

Acidosis Alcoholism Lead poisoning Leukemia Nephrolithiasis Polycythemia vera Renal failure Toxemia of pregnancy Purine-rich diet Excessive exercise Chemotherapy-related side effects

Drugs that Can Increase The Level Of Uric Acid by decreasing renal excretion::

Alcohol Ascorbic acid Aspirin >2 g/day Diazoxide Diuretics Epinephrine Ethambutol Levodopa Methyldopa

Drugs that Can Increase The Level Of Uric Acid by increasing production:

Cisplatin

Lower-than-normal levels of uric acid may be due to:

Fanconi syndrome Wilson's disease SIADH Low purine diet Multiple sclerosis

Drugs That Can Decrease The Level Of Uric Acid by increasing excretion:

Azathioprine Corticosteroids Estrogen Probenecid Warfarin Aspirin dose>4g/day

Drugs That Can Decrease The Level Of Uric Acid by decreasing production:

Allopurinol

SERUM URIC ACID ESTIMATION

PRINCIPLE:

Calorimetric assay, endpoint method Uricase Uric acid + 2H2O + O2 Allantoin + CO2 + H2O2

Uricase cleaves uric acid to form allantoin and hydrogen peroxide. POD 2H2O2 + 4H+ + phenole + Aminoantipyrine Quinonimine dye + 4H2O

REAGENT:

R1:

Phosphate buffer pH 8.0 Chlorophenol

R2:

Uricase POD 4-aminoantipyrine Preservative

Standard: Uric acid

WORKING REAGENT:

Dissolve contents of enzyme reagent R2 with the corresponding volume of buffer R1.

Gently swirl until completely dissolved. DO NOT SHAKE. Label it as Working reagent.

SPECIMEN:

Collect serum using standard sampling tubes. Heparin or EDTA plasma. Separate serum or plasma from the clot or cells within

one hour and analyze immediately, or store as follows:< 5 days ------------- at + 2 0C to 8 0C

6 months ----------- at -20 0CCentrifuge samples containing precipitates before performing the assay.

TESTING PROCEDURES:

Materials provided: Working solution as described above Additional materials required calibrators and controls as indicated below 0.9% NaCl

Manual procedure: Wavelength: Hg 546nm(490-550nm) Temperature: +250C / +30 0C / +370C Cuvette: 1cm light path Zero adjustment: reagent blank

B S USample - - 40 µl Standard - 40 µl -Working reagent 1000 µl 1000 µl 1000 µl

Mix and incubate for 5 minutes at 37 0C. Read the absorbance against blank within 30 minutes.

CALCULATIONS: ∆A Sample = _____________

∆A Standard = _____________

Conc. of Standard = 6mg/dl

Uric acid conc. in mg/dl = ∆A Sample × Conc. Of Standard

∆A Standard

=

Uric acid in mg/dl = ______________