When to take a blood test after a gout attack

Question

Gout is caused by an elevated level of uric acid in the blood, which results in crystals forming in the joints. Once this reaches a critical level, the body responds by targeting the crystals, resulting in inflammation and severe pain.

When there is suspicion that a patient has gout, he is typically sent for a blood test, to evaluate his blood level of uric acid. What I am wondering, is whether it matters how long after a gout attack this blood test is taken?

As such, which of the following statements are true:

1) During a gout attack, the level of uric acid in the blood drops due to the body's response to remove the crystals. Therefore, the patient should have the blood test several weeks after the attack, to ensure the uric acid levels are back to their stable level. It doesn't matter what the patient eats during these weeks, because the uric acid level is dependent on long-term dietary habits, rather than the very recent diet.

2) Similar to 1), the patient needs to wait a few weeks before the blood test. However, the patient also needs to ensure that he eats according to his "standard" diet during this period, because uric acid levels are dependent on short-term dietary habits. For example, if the patient cuts down on foods causing the uric acid during this period (e.g. red meat and alcohol), then the level of uric acid during the test will not be a typical measurement.

3) The level of uric acid does not decrease dramatically after a gout attack, and the blood test can be taken soon after.

Thanks!

Answer 1

Diagnosis of gout is based on clinical examination and arthrocentesis (to detect the presence of monosodium urate crystals in the synovial fluid).

The use of serum uric acid (sUA) levels is limited in acute gout flare and can be difficult to interpret. If acute gout attack is suspected in a patient, an elevated sUA (≥6.8 mg/dL) can lend support to the diagnosis but is neither diagnostic nor required to establish the diagnosis. Normal sUA levels have been reported in patients with acute gout flare 1

To your question:

The most accurate time for assessment of serum uric acid levels (and establishment of a baseline value) is two weeks or more after complete subsidence of an acute gout flare.

Sources:

Becker MA. Clinical manifestations and diagnosis of gout. UpToDate. Jun 2016. http://www.uptodate.com/contents/clinical-manifestations-and-diagnosis-of-gout

Hainer BL et al. Diagnosis, treatment and prevention of gout. Am Fam Physician. 2014 Dec 15;90(12):831-6.