Uric Acid

Overview

Uric acid measures serum concentration of the final enzymatic product of purine metabolism, primarily excreted by kidneys. It functions as an antioxidant at physiological levels but forms crystals causing gout at supersaturation. Elevated levels indicate gout, tumor lysis syndrome, renal failure, or Lesch-Nyhan syndrome, while low levels rarely cause symptoms but occur in Wilson’s disease or siRNA therapy; clinically useful for diagnosing hyperuricemia, monitoring urate-lowering therapy, and assessing risk of uric acid nephropathy or nephrolithiasis.

Clinical Use Cases

  • Diagnosing primary and secondary gout.
  • Monitoring allopurinol or febuxostat therapy efficacy.
  • Evaluating tumor lysis syndrome in hematologic malignancies.
  • Assessing renal handling of uric acid (fractional excretion).
  • Screening for inborn errors of purine metabolism.

Specimen Types

  • Serum.
  • Plasma (heparin).
  • Urine (24-hour collection).

Measurement Methods

  • Enzymatic uricase-peroxidase colorimetric assay.
  • Automated clinical chemistry analyzers.
  • High-performance liquid chromatography (HPLC).

Test Preparation and Influencing Factors

  • Fasting preferred; avoid high-purine foods 24 hours prior.
  • Recent alcohol consumption, dehydration elevate levels.
  • Diuretics, low-dose salicylates, pyrazinamide increase uric acid.
  • Allopurinol, probenecid, rasburicase lower levels.
  • Acute gout attack elevates levels nonspecifically.

Synonyms

  • Serum urate.
  • UA.

Further Reading

  • “Uric Acid Test” – MedlinePlus, NIH –