Discover the Acute Gout Diagnosis Rule!

As part of our mission to help physicians discover new calculators that may help them in their practice (and potentially reduce unnecessary testing and provide better, more evidence-based, efficient and safer care to patients) we’re starting a new series to update physicians about new calculators added to the site that they may not be aware of.

First up, a disease that is near and dear to many physicians’ joints: gout!

TL;DR: The Acute Gout Score is a validated decision instrument that aims to reduce unnecessary testing for gout (we’re talking joint aspiration), encourage appropriate testing, and prevent other critical arthritis diagnoses from being missed. That’s pretty much everything you want from a score like this.

The Background and Goals: Gout is often diagnosed clinically by physicians, so researchers wanted to know — how good are physicians at this? They also wanted to see if they could improve this diagnosis and help risk stratify patients into high risk groups that could be safely started on gout treatment, medium risk groups that would benefit the most from joint aspiration (which is often painful, and does carry some risk), and low risk groups where it’s probably not gout and other causes of joint pain should be explored.

gout photo The Study: They took patients with monoarthritis and asked them a bunch of questions, examined them, took blood work, and then tapped everyone’s painful joint (the gold standard) and then looked to see which criteria predicted gout. They also asked physicians to predict which patients had gout, to see how good physicians are compared to the score.

The Results: The variables in the score were obviously the most associated with gout, with a high serum uric acid level being the most predictive, followed by the affected joint being the big toe’s metatarsophalangeal. (Tophus prescence was actually the most predictive — 100% — but was a pretty uncommon finding (12.9%).)

So they pulled out tophus (figuratively; that would hurt otherwise), and then ran a bunch of statistical analyses, and found that the rule was very good, with an AUC of 0.85 if you used labs, and 0.82 if you didn’t have lab results.

This score then got validated in another (ethnically similar) population. Gout was very likely in patients with a score of ≥8 (80% of these patients had gout), and was very unlikely in patients with a score ≤4 (only 2.8%). (The score did better than these family physicians, by the way.)

Our Take: If you’re sure it’s gout, you’re probably right. But if you have any concerns or thoughts that it might not be, or something isn’t totally fitting, try this score. It can help you figure out who you should probably tap or at least follow closely if they’re not improving or worsening — and in which patients you should broaden your differential, because it probably isn’t gout at all.