Updated classification to include imaging techniques in the diagnosis of gout may help to standardise care.
INTRODUCTION
Gout is a very common condition. The symptoms tend to flare every so often, developing over a few hours and causing severe pain in the joints. It is caused by deposits of crystals of a substance called uric acid (urate) in the joints, which leads to inflammation. Classification criteria help doctors to diagnose conditions and treat them in a standard way and are particularly important for planning clinical trials for new treatments.
WHAT DID THE AUTHORS HOPE TO FIND?
The existing classification criteria for gout were developed before modern imaging techniques such as ultrasound were available to look for uric acid crystals. The authors wanted to see if they could work out what features of gout are best to distinguish it from other similar conditions in order to update the classification and help doctors to diagnose gout more easily.
WHO WAS STUDIED?
The study included case studies of 30 people with diagnosed gout, confirmed by the presence of uric acid crystals in their joints or skin nodules, and people without uric acid crystals, but with symptoms similar to gout.
HOW WAS THE STUDY CONDUCTED?
The study had several parts. To begin with the authors asked doctors who were familiar with gout what features they thought were important to distinguish gout from other conditions. Then 938 consecutive patients with gout-like symptoms from 16 clinics were identified and split into two groups, depending on whether they had deposits of uric acid crystals or not. The authors then reviewed the published medical literature to understand the accuracy of imaging techniques such as ultrasound and compared case studies of 30 patients with and without ‘crystal-proven’ gout to determine which features best distinguish gout from other conditions that are similar to gout. Finally, all the information was summarised to give a way of classifying gout.
WHAT WERE THE MAIN FINDINGS OF THE STUDY?
The authors identified ways to distinguish gout from other conditions that may be similar to gout. These include patient symptoms, physical examination findings, serum uric acid levels, joint fluid analysis, X-ray and imaging. In addition, the classification criteria that have been developed can be used even if joint fluid or imaging information is not available. To be suspected of having gout, a person must have had at least one episode of swelling, pain or tenderness in a peripheral joint. The diagnosis is confirmed if there are uric acid crystal deposits in a painful joint, or white deposits of crystals in nodules on the skin (tophus). If a person has an episode of swelling but does not have crystal deposits, then gout may also be diagnosed if they have pain or redness over the joint or can’t bear touch or pressure, or if pain comes on suddenly within a day, but goes away again within 2 weeks. Some laboratory tests can also confirm the diagnosis, as well as imaging with ultrasound or DECT.
ARE THESE FINDINGS NEW?
Yes, these are the first classification criteria for gout that have incorporated advanced imaging techniques such as ultrasound.
HOW RELIABLE ARE THE FINDINGS?
Classification criteria are not meant to be able to identify all possible cases of gout, and they may not work for unusual cases. But they should help doctors to identify the majority of people with gout in a standardised way.
WHAT DO THE AUTHORS PLAN ON DOING WITH THIS INFORMATION?
This information will be used to help plan new studies of gout so that the right sorts of patients are included. More studies are planned to see how these new criteria work in different settings.
WHAT DOES THIS MEAN FOR ME?
These new classification criteria will become the new standard for clinical studies of gout, and will help decide who should be enrolled into clinical trials. The new criteria will hopefully make it easier for more studies of gout to be conducted, and you may find you are asked to take part in trials for new treatments. It is very likely that the authorities and agencies that regulate the use of drugs will adopt these criteria as the standards they expect new drugs to be tested with, especially since these criteria have been developed in collaboration between the two major rheumatology organisations (ACR and EULAR).
On a day-to-day basis the criteria will not affect most people with gout, but they may have a bearing on how gout is managed and treated in the future.
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Date summary prepared: November 2015
Summary based on research article published on: 1 October 2015
From: Neogi T, et al. 2015. Gout classification criteria: An American College Of Rheumatology/European League Against Rheumatism collaborative initiative. Ann Rheum Dis 2015;74:1789–98. doi:10.1136/annrheumdis-2015-208237.
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