DESCRIPTION:
Uric acid is the final product of exogenous and endogenous purine metabolism. Humans excrete uric acid as the final metabolic product of purines. Uric acid is eliminated from circulation primarily in urine (approximately 75%), while approximately 25% is excreted into the intestine, where it is broken down by intestinal bacteria.
DETERMINATION:
Urates are determined by photometric method with uricase and ascorbate oxidase. Sample: Serum, plasma (heparin), or 24-hour urine. Serum or plasma stability is 5 days at 2°C–8°C, 6 months at -20°C. 24-hour urine stability is 4 days at 4°C–25°C.
CLINICAL SIGNIFICANCE:
In serum 1) Physiological changes in serum uric acid concentration Endogenous synthesis produces approximately 350 mg of uric acid daily, with an additional approximately 300 mg/day obtained from food. In plasma at pH 7.4, uric acid exists in ionized form as monosodium and monopotassium urate, with only a small portion as free acid. A) In renal tubules, approximately 90% of uric acid filtered in the glomeruli is normally reabsorbed. Uric acid is normally excreted from the body via the kidneys (80%) and intestines (20%). Approximately 4.76 mmol (800 mg) is excreted daily. B) After intense physical exertion, a significant increase in uric acid occurs. C)
After fasting and a high-fat diet, serum uric acid concentration increases. 2) Pathological changes in uric acid concentration A) Elevated uric acid values in: Athetoid cerebral palsy with mental retardation and self-mutilation / Coronary artery disease / Heavy chain disease / Diabetic ketoacidosis after intravenous fructose administration / Gout / Hemolytic anemia / Type III hyperlipoproteinemia / Massive tissue destruction / Myeloid leukemia / Mongolism (some cases) / Excessive ethanol intake / Lead poisoning / Pernicious anemia (especially after therapy) / Pneumonia / Primary hyperoxaluria / Primary and secondary polycythemia / Tangier disease (A-α-lipoproteinemia) / Pyrazinamide therapy / Uremia / Von Gierke’s glycogen storage disease B) Decreased uric acid concentration values in: Acromegaly (some cases) / Fanconi syndrome / Hepatolenticular degeneration / Xanthinuria / Use of uricosuric drugs.
In urine 1) Physiological changes in uric acid concentration in urine Uric acid is excreted from the body primarily in urine (approximately 75%). From the glomerular filtrate, uric acid is almost completely reabsorbed in the proximal tubules. Urates in final urine originate from active secretion of uric acid in the distal tubules. Urinary urate excretion increases after consuming purine-rich foods or with abundant xylitol intake, and decreases with consumption of foods rich in carbohydrates and fats but low in proteins. 2) Pathological changes in uric acid concentration in urine A) Elevated uric acid concentration values in urine in: Acute lymphoblastic leukemia / Acute myeloid leukemia / Sickle cell anemia without crisis (Sickle cell disease) / Bacterial meningitis / Bipolar affective disorders / Cerebral embolism / Cerebral hemorrhage / Cerebral thrombosis / Cerebral infarction / Cystinosis / Encephalomyelitis / Familial periodic paralysis / Gout, podagra; role / Hepatolenticular degeneration (Wilson’s disease) / Chronic myeloid leukemia / Lesch-Nyhan syndrome / Myelofibrosis / Osteomalacia / Paranoid personality disorder and other psychoses / Polycythemia rubra vera / Proximal renal tubular acidosis / Regional enteritis / Neonatal respiratory system conditions / Tuberculous meningitis / Ulcerative colitis / Viral hepatitis B) Decreased uric acid concentration values in urine in: Vitamin B12 deficiency anemia / Xanthinuria / Toxic effects of lead and its compounds
RISK FACTORS:
Decreased values:
– Menstrual cycle (luteal phase) – Pregnancy
Elevated values:
– Alcoholism – Fasting Summer – Protein-rich food 12 hours before blood collection – Purine-rich diet (organ meats) – Obesity – Stress – Shock – Physical exertion – Trauma – Fever
DRUG EFFECTS:
Decreased values:
Uric acid in serum: ascorbic acid, carbamazepine, cefotaxime, cyanides, dipyrone, phenylmercuric acetate, hydralazine, chloramphenicol, chlorine, levodopa, methyldopa, methotrexate, novaminsulfon, piperazine, tetracyclines Uric acid in urine: ascorbic acid, hydralazine
Increased values:
Uric acid in serum: acetaminophen, acetylsalicylic acid, aminophenol, ampicillin, ascorbic acid, aspirin, cystine, dextran, ergothioneine, etoposide, phenelzine, hydralazine, isoniazid, chloral hydrate, levodopa, mercaptopurine, methyldopa, oxyphenbutazone, oxytetracycline, propylthiouracil, protocatechuric acid, rifampin, potassium salts, sulfonamides, theophylline, tetracyclines, thiouric acid (6-mercaptopurine metabolite), thionein Uric acid in urine: acetaminophen, aspirin, ergothioneine, levodopa, methyldopa, protocatechuric acid, theophylline
RESULTS:
The reference interval depends on sex, age, and determination method. The reference interval is displayed on each validated result.
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