Validation Study of Physical Measurement of Tophi

Gout is a chronic urate crystal deposition disorder. Left untreated, gout may result in progressive disease characterized by joint and bone destruction from tophaceous deposits and renal impairment due to gouty nephropathy. Hyperuricemia, defined as a serum urate concentration greater than 7.0 milligrams per deciliter (mg/dL), is the underlying metabolic aberration leading to urate crystal deposition in gout. Gout has several clinical presentations, including: recurrent acute attacks of inflammatory arthritis; deposition of monosodium urate monohydrate crystals in joints, bones and even parenchymal organs (tophaceous gout); renal impairment; and uric acid nephrolithiasis.1 As serum urate levels increase beyond greater than 7.0 mg/dL, the risks for gouty arthritis or for renal calculi increase.

Febuxostat is a 2-aryl-thiazole derivative chemically engineered as a novel xanthine oxidase/dehydrogenase inhibitor. Febuxostat is being developed as an orally administered agent for the management of hyperuricemia in patients with gout.

Subjects with palpable tophi >10 millimeters (mm) in length and width and as round as possible will have the tophus measured on two separate visits by two different raters to assess the inter- and intra-rater reproducibility of direct physical measurement.

Inclusion criteria

• Must have at least 1 palpable gouty tophus nodule in the foot/ankle, hand/wrist, or elbow, confirmed as gouty by prior diagnosis according to ACR criteria.
• The tophus must be solid, round, non-tender, intact, and larger than 10mm in both length and width.
• Joints nearest and immediately adjacent to the selected tophus must not be acutely inflamed.
• Must be on stable treatment for gout with no medication changes in the past 30 days.

Exclusion criteria

• Must be able to return to the clinical site within 10 days.
• Must not have allergy to ink.