The Gout-calculator may not be sufficient enough, to replace arthrocentesis for synovial fluid analysis, for the diagnosis of gout or to exclude the possibility of septic arthritis in patients with acute arthritis, according to study results published in Clinical Rheumatology.
Gout flare, defined as an attack of synovitis, typically involves the hallux metatarsal joint. Evidence of sodium urate crystals in synovial fluid is the gold standard for the diagnosis of gout. However, as gout flares can involve larger and less distal joints, the diagnosis of gout may be difficult. In addition, it is also important to rule out septic arthritis.
The objective of the current study was to determine the performance of the Gout-calculator in patients with acute arthritis affecting large and intermediate joints, without an attack on the hallux or midfoot joints.
The cross-sectional study included 233 adults with acute arthritis (SYNOLACTATE cohort) from the Rheumatology Department of the University Hospital of Rennes, France. Researchers determined the Gout-calculator score for 170 patients of the total cohort, including 40 patients with gout and 130 with other diagnoses of acute arthritis.
Among patients with a diagnosis of gout compared with those with other etiologies of acute arthritis, there were significantly more men (85% vs 65%, respectively; P =.02), with oligoarticular involvement (47.5% vs 29.5%, respectively; P =.03) and a shorter evolution (5.7 vs 8.5 days, respectively; P =.02).
Several variables were associated with the diagnosis of gout, including serum uric acid greater than 350 µmol/L (odds ratio [OR], 5.52; 95% CI, 2.52-12.1; P <.001), joint redness (OR, 5.08; 95% CI, 1.85-1.40; P =.001), previous patient-reported arthritis attack (OR, 4.04; 95% CI, 1.92-8.49; P <.001), being men (OR, 3.00; 95% CI, 1.17-7.69; P =.02), and hypertension or cardiovascular disease (OR, 2.33; 95% CI, 1.07-5.06; P =.03).
The median Gout-calculator score was significantly higher in gouty arthritis (7.0 [interquartile range (IQR), 5.5-8.1]) than in associated-calcium pyrophosphate acute arthritis (4.0 [IQR, 2.0-5.8]), septic arthritis (3.0 [IQR, 2.0-5.1]), or other arthritis (3.5 [IQR, 2.0-5.5]).
For a Gout-calculator threshold of 4 or less, the sensitivity was 92.5%, specificity was 50.8%, and likelihood ratio was -0.15 to gout diagnosis. For a Gout-calculator threshold of 8 or greater, the sensitivity was 27.5%, specificity was 97.7%, and likelihood ratio was +11.9 to gout diagnosis.
“Despite diagnostic performances close to those published in other cohorts, the use of the Gout-calculator is not sufficient for the diagnosis of gout or to exclude the differential diagnosis of septic arthritis in our consecutive acute arthritis cohort,” the researchers concluded.
Robin F, Berthoud O, Albert JD, et al. External validation of Gout-calculator performance on a cohort of acute arthritis (SYNOLACTATE) sparing distal joints such as hallux and midfoot. A cross-sectional study of 170 patients. Clin Rheumatol. Published online, October 28, 2020. doi:10.1007/s10067-020-05382-z