Uric Acid

Uric acid is a metabolic end product from purine metabolism, approximately 80% of which is excreted by the kidneys (urinary). The laboratory parameter belongs to the renal retention parameters. It is used to assess the performance of the kidneys. An increase indicates impaired kidney function, as the substance is retained in the body (retention). If the solubility product for sodium urate is exceeded, uric acid crystallizes and can then lead to gout and/or nephrolithiasis (kidney stones).

The process

Material needed

  • 0.5 ml blood serum (preferred)
  • 0.5 ml lithium heparin plasma

Preparation of the patient

  • No preparation necessary

Disruptive factors

Normal values adults

Gender Normal value in mg/dl
Female 2,4-5,7
Male 3,4-7,0

Hyperuricemia: > 390 μmol/l (6.5 mg/dl)

Normal values children

Gender Age Normal value in mg/dl
Female 1st week of life 1,9-7,9
1st-4th year (LY) 1,7-5,1
5-11 LY 3,0-6,4
12-14 LJ 3,2-6,1
15-17 LJ 3,2-6,4
Male 1st week of life 1,9-7,9
1ST-4TH LJ 2,2-5,7
5-11 LY 3,0-6,4
12-14 LJ 3,2-7,4
15-17 LJ 4,5-8,1

Conversion factor: uric acid mg/dl x 59.485 = µmol/l

Indications

  • Suspected hyperuricemia – elevated uric acid levels in the blood.
  • Suspicion of gout attack

Interpretation

Interpretation of elevated values

Primary hyperuricemias (gout)

  • Renal elimination disorder (renal excretory disorders).
  • Endogenous urate overproduction
  • Lesch-Nyhan syndrome – hereditary disease of purine metabolism leading to urinary stones, but also neurological and psychiatric symptoms.

Secondary hyperuricemia (gout).

  • Fasting
  • High purine diet
  • Sugar substitutes (fructose, sorbitol, xylitol)
  • Alcohol consumption
  • Acromegaly – disease in which the body end limbs continue to enlarge due to increased growth hormone even after physiological growth is complete.
  • Glycogen storage disease type I
  • Hyperparathyroidism (parathyroid hyperfunction).
  • Hyperuricemia
  • Hypothyroidism (underactive thyroid gland)
  • Ketoacidosis – acidification of the blood with the formation of so-called ketone bodies.
  • Lactacidosis
  • Malignant tumors – malignant neoplasms.
  • Myeloproliferative neoplasms (MPN) (formerly chronic myeloproliferative disorders (CMPE)): e.g.
    • Chronic myeloid leukemia (CML).
    • Osteomyelosclerosis (OMS)
    • Polycythaemia vera (PV; synonyms: polycythemia, polycythemia).
  • Renal failure
  • Medication
    • Acetylsalicylic acid (ASA) (<1,000 mg/die); the lower the dose, the higher the risk of gout:
      • < 325 mg/die: 81% (OR=1.81, 95% CI 1.30-2.51).
      • ≤ 100 mg/die: 95% (OR=1.91, 95% CI 1.32-2.85)
    • Antihypoglycemics (diazoxide).
    • Antiphlogistics, nonsteroidal (oxyphenbutazone, phentylbutazone).
    • Beta-blockers (propranolol)
    • Diuretics
    • Ethambutol (antibiotic/tuberculostat).
    • Immunosuppressants (ciclosporin (cyclosporin A))
    • L-dopa
    • Nicotinic acid
    • Tuberculostatics (pyrazinamide)
    • Cytostatics
  • Radiotherapy
  • Intoxications (poisonings) – with lead, beryllium.

Interpretation of lowered values

  • Hepatopathy (liver damage)
  • Idiopathic/acquired tubule defects.
  • Xanthine oxidase defect
  • Medication
    • Glycerin/gujac-containing expectorants.
    • Estrogens
    • Phenylbutazone
    • X-ray contrast agent
    • Salicylates (> 3 g/die)
    • Xanthine oxidase inhibitors (allopurinol)

Other notes

  • In a study of early detection of kidney disease, it was found that men and women had a significantly reduced life expectancy if an elevated serum uric acid concentration was measured at the initial examination. In this statement, risk factors such as anemia (anemia), obesity, hyperlipidemia (dyslipidemia), metabolic syndrome, serum albumin, and inflammatory parameters, among others, were considered in the calculation.
    • Men: An adjusted hazard ratio of 2.7 was measured for a serum uric acid level of 9 mg/dl (535 µmol/l), which was significant with a 95% confidence interval of 1.91 to 4.02. A uric acid level of less than 4 mg/dl (238 µmol/l) was also associated with a significantly increased mortality/sterility risk (adjusted hazard ratio 2.32; 1.53 to 3.27). This had a major impact on lifespan: men with elevated serum uric acid levels died on average 11.7 years (7.27 to 16.92) earlier. Low levels was also associated with a reduced lifespan by 9.52 years (4.38 and 15.53).
    • Women: This showed a J-curve: a serum uric acid level above 7 mg/dl (416 µmol/l) was associated with a 69% increased risk of mortality/sterility (adjusted hazard ratio increased 1.69; 1.13 to 2.47). Women with high serum uric acid levels died approximately 9 years (0.97 to 12.32) earlier.

    Note: Uric acid has an antioxidant effect that takes place at low levels. Why this effect takes place significantly in men and not in women, can not be explained so far.