From the Guidelines
Yes, uric acid levels can drop during an acute gout attack. This occurs because during an acute attack, uric acid crystals move from the bloodstream into the joints, causing inflammation and pain. As these crystals leave the circulation, serum uric acid levels may temporarily decrease.
Key Points to Consider
- This phenomenon makes it unreliable to diagnose gout based on uric acid levels measured during an acute attack.
- For accurate diagnosis and management, it's better to measure uric acid levels 2-4 weeks after an acute attack has resolved.
- Urate-lowering therapy (such as allopurinol starting at 100mg daily and gradually increasing, or febuxostat 40-80mg daily) should not be initiated during an acute attack but rather after it has resolved, while continuing prophylactic anti-inflammatory medication.
- The temporary drop in serum uric acid during attacks explains why some patients with severe gout may occasionally show normal uric acid levels when tested during an acute episode, as noted in studies 1.
- High-quality evidence shows that prophylactic therapy with low-dose colchicine or low-dose NSAIDs effectively reduces acute gout flares in patients initiating urate-lowering therapy, and moderate-quality evidence supports continuing prophylactic therapy for more than 8 weeks 1.
- The American College of Physicians recommends discussing benefits, harms, costs, and individual preferences with patients before initiating urate-lowering therapy, including concomitant prophylaxis, in patients with recurrent gout attacks 1.
From the Research
Uric Acid Levels During Acute Gout Attacks
- Uric acid levels can drop during an acute gout attack, as seen in a study published in 2023 2, which found that serum uric acid (SUA) levels were significantly lower during the acute phase of gout compared to after the flare.
- Another study from 2014 3 found that 63.3% of patients with acute gout attacks had normal serum uric acid levels, suggesting that a normal uric acid level does not exclude the diagnosis of an acute gout attack.
- A 2020 study 4 compared clinical features of normouricemic and hyperuricemic patients with gout and found that normouricemic patients had higher inflammatory activity, but the recurrence rate of gout attacks was not different between the two groups.
Factors Influencing Uric Acid Levels
- Inflammatory factors, such as C-reactive protein, and bioactive free glucocorticoids may play a significant role in the decrease of SUA levels during an acute gout flare 2.
- The 24-hour fractional excretion of uric acid and 24-hour urinary uric acid excretion were increased significantly in patients during the acute phase of gout 2.
- A study from 2009 5 found that patients taking chronic allopurinol were more likely to have lower SUA levels at baseline compared to those not taking chronic allopurinol during an acute attack.