From the Guidelines
Low urate levels are typically considered to be below 6.0 mg/dL, as achieving serum urate levels less than this threshold is associated with a reduced risk of acute gout attacks. According to a post hoc analysis that combined data from 3 large trials (ULT, FACT, and APEX) 1, patients who achieved a serum urate level less than 357 µmol/L (<6.0 mg/dL) at the end of 1 year had a risk for acute gout attacks of approximately 5%, whereas patients with levels at or above 357 µmol/L (≥6.0 mg/dL) had risks of about 10% to 15%.
Some key points to consider about low urate levels include:
- The relationship between achieved lower serum urate levels and reduced risk for acute gout attacks is supported by several studies, including analyses from retrospective cohort studies 1
- Higher urate levels are predictive of a subsequent acute flare, with an odds ratio of 1.35 [CI, 1.2 to 1.5] in one study that reported outcomes for a cohort of 158 patients with incident gout who were followed for a mean of 13 years 1
- There are potential nonarticular impacts of hyperuricemia in patients with gout that may be affected by serum urate levels, including a 2-fold difference in new diagnoses of kidney disease in patients with high versus low serum urate levels 1
In terms of clinical implications, achieving and maintaining serum urate levels below 6.0 mg/dL is a key goal in the management of gout, as it can help reduce the risk of acute gout attacks and potentially mitigate other nonarticular impacts of hyperuricemia. This can be achieved through a combination of lifestyle modifications, medications, and other interventions, as determined by a healthcare provider.
From the Research
Definition of Low Urate
- Low urate, also known as hypouricemia, is defined as a serum urate level of less than 2 mg/dL (119 µmol/L) 2, 3, 4.
Causes of Hypouricemia
- Hypouricemia can be caused by disorders of purine metabolism and transport, including hereditary xanthinuria and hereditary renal hypouricemia 2.
- Hereditary xanthinuria is an autosomal recessive disorder caused by mutations in xanthine oxidase, leading to over-production of xanthine and minimal production of urate 2.
- Hereditary renal hypouricemia is a genetic defect of renal transport of uric acid, which can be caused by defects in the SLC22A12 gene or the SLC2A9 gene 2, 3.
Clinical Significance of Hypouricemia
- Hypouricemia can be a biomarker of various pathological and potentially harmful conditions, and its diagnosis requires a deeper clinical investigation 4.
- Patients with hypouricemia may be at risk of exercise-induced acute kidney injury and urolithiasis, particularly those with renal hypouricemia 2, 3.