From the Guidelines
Diagnosing tophi requires a combination of clinical examination, laboratory testing, and imaging studies, with the most definitive approach being aspiration of the suspected tophus and examination under polarized light microscopy to reveal monosodium urate crystals, as recommended by the 2018 updated European League Against Rheumatism evidence-based recommendations for the diagnosis of gout 1. To diagnose tophi, a healthcare provider should first look for characteristic nodules under the skin, typically around joints, ears, or the olecranon bursa. These nodules are firm, painless, whitish-yellow deposits that represent urate crystal accumulations.
Key Diagnostic Steps
- Physical examination should focus on common sites including fingers, toes, elbows, and the outer ear.
- Aspiration of the suspected tophus and examination under polarized light microscopy is the most definitive approach to confirm the diagnosis, which will reveal needle-shaped, negatively birefringent monosodium urate crystals.
- Blood tests showing elevated serum uric acid levels support the diagnosis, though levels may be normal during acute attacks.
- Imaging studies such as ultrasound, dual-energy CT, or MRI can help identify tophi that aren't visible or palpable, as suggested by the 2012 American College of Rheumatology guidelines for management of gout 1.
Importance of Early Diagnosis
The presence of tophi indicates chronic gout, typically developing after years of hyperuricemia, and their identification warrants aggressive urate-lowering therapy to prevent joint destruction and disability. According to the 2018 updated European League Against Rheumatism evidence-based recommendations for the diagnosis of gout, searching for crystals in synovial fluid or tophus aspirates is recommended in every person with suspected gout, because demonstration of MSU crystals allows a definitive diagnosis of gout 1. Additionally, the guidelines suggest that plain radiographs are indicated to search for imaging evidence of MSU crystal deposition, but have limited value for the diagnosis of gout flare, while ultrasound scanning can be more helpful in establishing a diagnosis in patients with suspected gout flare or chronic gouty arthritis by detection of tophi not evident on clinical examination, or a double contour sign at cartilage surfaces, which is highly specific for urate deposits in joints 1.
From the Research
Diagnosis of Tophi
- Tophi are diagnosed mainly clinically, with imaging used to assess complications like bony erosions 2
- The American College of Rheumatology (ACR) guidelines indicate that urate-lowering therapy should be initiated in patients with the presence of tophi visible on examination or imaging 2
- Diagnosis of gout, which is characterized by the presence of tophi, can be made using several validated clinical prediction rules 3
- Arthrocentesis should be performed when suspicion for an underlying septic joint is present, and synovial fluid or tophus analysis should be performed if the diagnosis is uncertain 3
Clinical Presentation
- Tophi are stone-like deposits of monosodium urate in the soft tissues, synovial tissues, or in bones near the joints 2
- They are pathognomonic for gout, and are usually painless and rarely present as the initial manifestation of gout 2
- Gout is characterized by swelling, pain, or tenderness in a peripheral joint or bursa, including the development of a tophus 3
Diagnostic Criteria
- The presence of monosodium urate crystals in synovial fluid confirms the diagnosis of gout 4
- The diagnosis of gout can be made based on clinical presentation, laboratory tests, and imaging studies 4, 3
- Tophi are a key diagnostic feature of chronic gout, and their presence indicates a need for urate-lowering therapy 2, 3