The management of gout has always focused on checking and trying to lower the levels of uric acid (urate) in the blood.
However, emerging data show that it is the burden of the urate (uric acid) crystals in the soft tissues which is much more important than the levels in the blood.
A research paper published this month in Arthritis and Rheumatology (January 2020 issue) by Ellmann and colleagues found that both lifestyle changes and medications reduced the amount of gout crystal.
Lifestyle interventions in the study were:
Avoid the consumption of alcohol, in particular beer;
Avoid fructose‐containing beverages;
Avoid consumption of excessive meat and shellfish.
Patients were also advised to use an online calculator for the energy (including purine) content of the food. It was recommended in this study that purine consumption be limited to 200 mg/day.
They underwent dual-energy CT scans of the feet and ankle which can measure the amount of gout crystal deposited in the soft tissues.
They found that the crystals were deposited in the soft tissues much more than in the joints. The levels of crystal deposition improved with those who followed the lifestyle intervention recommendations as well as those who took medication, but not in those who just carried on as they were.
Those who undertook lifestyle changes were able to reduce their serum urate by only 30 micromol/l. The normal range is 200-400 and their urate levels reduced from 428 to 399. Those taking allopurinol reduced their urate from an average of 416 to 327 micromol/l.
However, the changes in the burden of urate crystals in the soft tissues of the foot and ankle were only weakly reflected by changes in the serum levels of uric acid.
The deposition of these crystals is important. It tends to occur before a patient is aware of any symptoms at all. It has also been shown to be associated with increased hardening (calcification) of coronary arteries, which is associated with heart disease.
The crystal deposits can be detected using ultrasound or dual-energy CT scans. These are not yet being used routinely in the clinic, but the way we are thinking about gout is slowly changing, so watch this space and realize that the blood levels of uric acid only tell a small part of the story!
Commentaires