Chemical Pathology

Notes

  • Uric acid (urate) is produced following breakdown of purines (either from the diet or from the normal breakdown of cells in the body). Uric acid is removed by the kidneys and excreted in the urine and faeces.
  • Uric acid is measured in patients with inflammatory arthropathies, although not all patients with hyperuricaemia have (or will develop) gout. The diagnosis depends on the demonstration of synovial fluid uric acid crystals in the presence of inflammatory cells.
  • Uric acid is also used for the investigation/monitoring of pre-eclampsia and sometimes following chemotherapy or radiation treatment.
  • Elevated uric acids levels will be seen in renal failure. Raised levels are also seen with excessive use of alcohol, starvation, a high-protein diet and strenuous exercise. Elevated levels are also seen in the rare inherited disorder, Lesch-Nyhan syndrome,
  • Low uric acid levels may indicate severe liver disease, low protein diet, heavy metal poisoning, Wilson's disease or some type of cancer.
  • Many drugs can affect uric acid levels. For example, raised levels are caused by thiazide diuretics, theophylline and low dose aspirin; low levels are caused by high dose aspirin, corticosteroids and allopurinol. Rasburicase continues to breakdown uric acid in the blood sample in vitro and levels assayed may not represent the in vivo situation.

Sample requirements

For adults, blood taken into a 5mL gold top gel tube ((or rust top for the Acute Unit)

5ml gold tube

For children, blood taken into a 3.5mL rust top gel tube

3.5ml rust top tube

For neonates, blood taken into a 0.8mL minicollect lithium heparin tube. Please list the tests of particular interest so that some priority can be given to analysis if plasma volumes are small.

Minicollect lithium heparin tube

Storage/transport

Store refrigerated if unable to send to the laboratory the same day. Transport as soon as possible at ambient temperature.

Required information

Include relevant clinical details, relevant drugs, known or possible diagnoses and whether the patient is pregnant (including the stage of pregnancy).

Turnaround times

The assays are run throughout the day and night. The in-lab turnaround time is always less than 24 hours. The test can be ordered as an urgent request.

Reference ranges


Gender/Age Reference Range (µmol/L)
Males/females <12 years old 120 – 340
Males >12 years old 200 – 430
Females >12 years old 140 – 360

Further information

To learn more about uric acid, visit Lab Tests Online or access the uric acid monograph of the Association for Clinical Biochemistry and Laboratory Medicine

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