New Staging System Proposed for Gout

Dalbeth N, Stamp L. Hyperuricaemia and gout: time for a new staging system? Ann Rheum Dis. 2014 Apr 9. doi: 10.1136/annrheumdis-2014-205304. [Epub ahead of print]

A proposed new staging system for gout emphasizes that advanced imagingmay be needed to detect signs of monosodium urate (MSU) crystal deposition to confirm a diagnosis -- with or without signs and symptoms of gout.

The current and widely-used clinical staging system for hyperuricemia (elevated serum urate), gout, flares, and gouty arthritis may describe symptoms adequately, say these authors from New Zealand, but it does not delineate its pathological basis, MSU crystal deposition.

The present system classifies gout into three stages:

• Acute gouty arthritis, asymptomatic chronic hyperuricemia leading to MSU crystal deposits in joints and acute inflammatory arthritis.
• Intercritical gout, the period between acute gout attacks and subsequent attacks without needing treatment.
• Chronic tophaceous gout, associated with the presence of tophi and bone/joint damage, usually after gout has been present for years.

The flaw in this system is that imaging with ultrasound (US) or and dual-energy CT (DECT) is needed to spot and analyze MSU formation, crystal deposition in joints, and gouty tophi, which may not produce symptoms.

These authors propose a four-part staging system delineating a disease spectrum:

• Stage A: High risk for gout, or hyperuricemia without evidence of MSU crystal deposition or gouty symptoms
• Stage B: MSU crystal deposition by microscopy or advanced imaging, but without signs or symptoms of gout. This stage would encompass indiviuals who display the double contour sign on US, urate deposition on DECT, and MSU crystals seen with microscopy
• Stage C: MSU crystal deposition with prior or current symptoms of acute gout flares (for example, people with a current or previous flare)
• Stage D: Advanced gout requiring specialist interventions, encompassing people with tophi, chronic gouty arthritis and radiographic erosions

The proposed system, they argue, would provide a reason to screen of asymptomatic disease, afford a clear focus on gout as a chronic disease of MSU crystal deposition, and establish a rationale for treating asymptomatic disease.

On the latter topic, a report this week in JAMA Internal Medicine highlights the risks of treating asymptomatic hyperuricemia with allopurinol, which it says is contrary to guidelines but nonetheless widespread.

The article recounts seven cases of such unnecessary treatment reported to an Italian monitoring center. One was fatal, a hypersensitivity reaction in a 81-year-old woman with no major health problems or gout history was diagnosed with asymptomatic hyperuricema based on a serum uric acid of 6.6 mg/dL and creatinine 2.31 mg/dL on “routine screening”.

Evidence supports allopurinol for asymptomatic hyperuricemia in three conditions: (1) uric acid above 13 mg/dL in men or 10 mg/dL in women, which has nephrotoxic risks (2) urinary excretion of uric acid >1,100 mg daily, which is associated with an increased risk of uric acid calculi (3) patients about to receive radiation or chemotherapy to prevent uric acid nephropathy from tumor lysis syndrome.