The guidelines put forth 10 diagnostic criteria for gout, ranked not only upon extant research but also on benefit and risk, cost, and the clinical expertise required to effectively use the criteria.
“This seems a better system, reflecting both research evidence and expert opinion, than the traditional semiautomatic estimation based on category of research data alone,” wrote Dr. Weiya Zhang of the University of Nottingham (England), who led a 20-person panel in developing the document.
The recommendations were drawn from the same 181 studies, published from 1945 to 2005, from which the EULAR panel drew its 12 gout management recommendations (see accompanying story).
The recommendations address clinical, biochemical, and radiographic diagnostic techniques for the disease:
1.IClinical symptoms of rapidly developing severe joint pain and swelling, especially with overlying erythema, are highly indicative of crystal formation but have low sensitivity (23%) for a gout diagnosis without further evidence.
2.IMonosodium urate monohydrate (MSU) crystals in synovial aspirate have both high sensitivity and high specificity, although variability in lab expertise may affect the accuracy of the sample findings.
3.IA clinical diagnosis of classic recurrent podagra with hyperuricemia can be reasonably assumed to be gout but requires MSU crystal confirmation.
4.IAll patients with inflamed joints should have their synovial fluid examined for MSU crystals.
5.IMSU testing can also be performed between bouts of inflammation, because urate crystals persist in intercritical periods in up to 70% of patients.
6.IBecause gout and sepsis may occur simultaneously, all possible gout patients should also have Gram staining and culture of synovial fluid. The test should be performed even if the fluid is positive for MSU crystals, because septic arthritis can progress rapidly and carries a significant risk of morbidity and mortality.
7.ISerum uric acid can't be used exclusively as a diagnostic tool. Many people with high serum uric acid don't develop gout, and some patients with confirmed MSU crystals have normal serum uric acid.
8.IGout patients under age 25 years who have a family history of the disease or who have renal calculi should have a 24-hour urinary uric acid/creatinine ratio done. The 24-hour screen appears to be more accurate and cost effective than an early morning spot sample.
9.IRadiographs might be useful for a differential diagnosis, but they can't confirm gout. There are radiographic changes in all stages of gout, but many affected joints can be radiographically normal. Patients with intradermal tophi are more likely to show severe radiographic changes.
10.IMale gender, diet, alcohol use, and diuretics increase the risk of gout, but don't ignore other important risk factors. These include hypertension (relative risk of 4, compared with controls), coronary heart disease (odds ratio, 1.75), chronic renal failure (odds ratio, up to 5), and obesity (odds ratio, 3.8).