Turnaround times
The quoted turnaround time is from sample receipt in the laboratory, to results authorisation in the Laboratory Information Management system. The times do not include transport of specimen to the laboratory or the administrative process to print and post/email reports. Service users must allow for transport and reporting time when ordering tests.
Clinical background:
Hyperuricaemia Causes
1. INCREASED PURINE SYNTHESIS – Primary gout, Lesch-Nyhan syndrome, Essential hyperuricaemia.
2. INCREASED NUCLEIC ACID TURNOVER – Myeloproliferative disorders and reticuloses. Following cytotoxic therapy. Chronic haemolytic states.
3. IMPAIRED RENAL CLEARANCE – Drugs – diuretics, small doses of salicylate. CRF. Hypertension. Pre-eclampsia.
4. CALCIUM INDUCED RENAL CLEARANCE – Hyperparathyroidism. Idiopathic hypercalcuria.
5. MISCELLANEOUS – Starvation. Ketoacidosis. Acute alcohol overdose.
Hypouricaemia Causes
1. DECREASED INTAKE – Low purine diet.
2. DECREASED PRODUCTION – Allopurinol. Xanthine oxidase deficiency. Purine nucleoside phosphorylase deficiency. Severe liver disease.
3. INCREASED CLEARANCE – Due to drugs eg high dose salicylate. Proximal tubule reabsorptive defect eg multiple myeloma. Wilson’s disease. Defect in renal urate transport eg Hodgkins, severe liver disease, SIADH, acute volume expansion.
Specimen container paediatric:
Serum sample (plain or SST)
Specimen container adult:
Serum sample (plain or SST)
Minimum volume paediatric:
0.5 mL blood
Minimum volume adult:
1 mL blood
Special requirements:
For patients on Rasburicase (recombinant urate oxidase).
The sample must be collected into a pre-chilled (refrigerated) lithium heparin tube.
Send sample on ice to the laboratory ASAP after collection.
Sample stability:
Unseparated: 7 days
Separated:
– 3 days at room temperature
– 7 days at 2 to 8C
– 6 months at -20C
Interpretation:
Uses and Interpretation
1. Gout: A diagnosis of gout in a patient with an acute inflammatory arthropathy is supported by the finding of a high level although it is not required for the diagnosis and may be absent. Patients with hyperuricaemia may develop inflammatory arthritis that is not gout. Although there is no agreed value above which hypouricaemia meds. are indicated, the risk of gout rises considerably at urate concentrations > 540umol/L. The aim of treatment is to maintain plasma levels of < 360umol/L.
2. Pre-eclampsia: Hyperuricaemia can be an early feature of pre-eclampsia but has poor specificity and sensitivity and is not used diagnostically.
3. Tumour lysis syndrome: Urate should be measured in patients undergoing chemotherapy with regimens known to carry a risk of tumour lysis.
4. Ethambutol treatment: Urate should be measured in patients on ethambutol.
Numerous factors tend to increase urate levels e.g, high purine intake, alcohol, obesity, hypertryglyceridaemia and impaired renal function. Modification of these factors can reduce the risk of gout.
Reference ranges:
Up to 7 days:
150 to 505 umol/L
7 days and over (Male): 200 to 430 umol/L
7 days and over (Female): 140 to 360 umol/L
Other info:
Lithium Heparin plasma sample also acceptable