Dynamic assessment of the double contour sign by ultrasonography helps to distinguish between gout and calcium pyrophosphate deposition disease
Authors' conclusion
The dynamic US assessment of the DC sign may help to differentiate the DC sign due to MSU crystals from the pseudo DC sign seen in CPPD, as they move in opposite directions.
Study context
- Population
- Patients with gout meeting the 2015 ACR/EULAR classification criteria and patients with crystal-proven CPPD81 gout, 84 CPPD · patients with crystal-proven CPPD 84
- Comparison
- Dynamic vs static ultrasound (US) assessment of the double contour (DC) sign for gout diagnosis
- Outcome
- Dynamic behaviour of the DC sign in gout and CPPD; diagnostic accuracy of the DC sign for gout
Methodological detailscross-sectional
- Cross-sectional
Performance
As reported in the abstract
Diagnostic performance of the DC sign for gout
| Test or model | Sensitivity | Specificity | Accuracy |
|---|---|---|---|
| Static DC sign | 58.0% (95% CI 46.5% to 68.9%)Sensitivity on a scale from 0 to 100 percent | 89.3% (95% CI 80.6% to 95.0%)Specificity on a scale from 0 to 100 percent | 73.9% (95% CI 66.5% to 80.5%) |
| Dynamic DC sign | — not stated in the abstract | 97.6% (95% CI 91.7% to 99.7%)Specificity on a scale from 0 to 100 percent | 78.2% (95% CI 71.1% to 84.2%) |
Sensitivity
Static DC sign58.0% (95% CI 46.5% to 68.9%)
Dynamic DC sign— not stated in the abstract
Sensitivity on a scale from 0 to 100 percentSpecificity
Static DC sign89.3% (95% CI 80.6% to 95.0%)
Dynamic DC sign97.6% (95% CI 91.7% to 99.7%)
Specificity on a scale from 0 to 100 percentAccuracy
Static DC sign73.9% (95% CI 66.5% to 80.5%)
Dynamic DC sign78.2% (95% CI 71.1% to 84.2%)
— not stated in the abstract
- Dynamic DC sign vs Static DC sign: P = 0.01 — improved without loss in sensitivity
Further findings
| Outcome | P value |
|---|---|
| Dynamic behaviour among patients with a DC sign (47 gout, 9 CPPD)Gout vs CPPD | P < 0.01 |
- Dynamic behaviour among patients with a DC sign (47 gout, 9 CPPD) — Gout: true DC sign on dynamic assessment
- 47/47
- Dynamic behaviour among patients with a DC sign (47 gout, 9 CPPD) — CPPD: pseudo DC sign on dynamic assessment
- 7/9 (77.8%)
Original publication
Dynamic assessment of the double contour sign by ultrasonography helps to distinguish between gout and calcium pyrophosphate deposition disease. RMD Open. Published 16 March 2023. doi:10.
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