From the Guidelines
An official diagnosis of gout is made through a combination of clinical evaluation and laboratory testing, with the gold standard being the identification of monosodium urate crystals in joint fluid. When a patient presents with symptoms like sudden, severe joint pain (typically in the big toe), redness, swelling, and warmth, a healthcare provider will first perform a physical examination. To confirm the diagnosis, the doctor will typically perform a joint fluid analysis (arthrocentesis) where fluid is extracted from the affected joint and examined under a polarized light microscope to identify the characteristic needle-shaped urate crystals 1. Blood tests are also conducted to measure uric acid levels, though elevated levels alone aren't sufficient for diagnosis as some gout patients have normal levels during attacks. Imaging studies such as X-rays, ultrasound, or dual-energy CT scans may be used to assess joint damage or identify urate crystal deposits. Additionally, doctors will consider the patient's medical history, including previous gout attacks, family history, diet, alcohol consumption, and medication use. The combination of crystal identification, clinical symptoms, and supporting laboratory findings provides the most accurate diagnosis of gout.
Key Diagnostic Criteria
- Identification of monosodium urate crystals in joint fluid
- Clinical symptoms such as sudden, severe joint pain, redness, swelling, and warmth
- Medical history, including previous gout attacks, family history, diet, alcohol consumption, and medication use
- Imaging studies to assess joint damage or identify urate crystal deposits
Laboratory Testing
- Joint fluid analysis (arthrocentesis) to identify monosodium urate crystals
- Blood tests to measure uric acid levels
- Imaging studies such as X-rays, ultrasound, or dual-energy CT scans to assess joint damage or identify urate crystal deposits
Clinical Evaluation
- Physical examination to assess joint pain, redness, swelling, and warmth
- Medical history to identify risk factors and previous gout attacks
- Consideration of patient's diet, alcohol consumption, and medication use
According to the American College of Physicians clinical practice guideline, synovial fluid analysis is recommended when clinical judgment indicates that diagnostic testing is necessary in patients with possible acute gout 1. The guideline also notes that the identification of monosodium urate crystals in joint fluid is the reference standard for diagnosing acute gout. A systematic review of diagnostic tests for gout found that the combination of clinical symptoms, laboratory findings, and imaging studies provides the most accurate diagnosis of gout 1.
From the FDA Drug Label
Patients meeting American College of Rheumatology criteria for gout
- The official diagnosis of gout is made based on the American College of Rheumatology criteria.
- No further information is provided on what these criteria entail. 2
From the Research
Diagnosis of Gout
An official diagnosis of gout can be made using several methods, including:
- Clinical criteria from the American College of Rheumatology, as mentioned in 3
- Identification of monosodium urate crystals in synovial fluid of the affected joint, as stated in 3, 4, 5
- Clinical prediction rules, as noted in 6
- Arthrocentesis and synovial fluid or tophus analysis, as recommended in 6 when suspicion for an underlying septic joint is present or when the diagnosis is uncertain
Laboratory and Radiologic Findings
Laboratory and radiologic findings can also be helpful in making a diagnosis of gout, including:
- Demonstrating the presence of monosodium urate (MSU) crystals in the joint fluid or tophus, as mentioned in 4
- Radiologic studies, as noted in 4
- Serum uric acid levels, although elevated levels are not always present, as stated in 5
Classification Criteria
Various classification criteria can be used to make a diagnosis of gout, including: