Background/Purpose

The gold standard for diagnosing gout and CCP arthritis is the identification of monosodium urate (MSU) crystals in joint fluid. Ultrasound (US) features of gouty and CPP arthritis have been described (1,2), and the technique has been proposed as a diagnostic tool in acute arthritis. There have been limited studies on the performance of this technique as a diagnostic tool when applied to the setting of acute arthritis

The primary objective was to determine the performance of ultrasound as a diagnostic tool for CCPD and urate acute crystal arthritis, using crystal identification by microscopy as a gold standard.

Methods

117 consecutive patients who presented an acute arthritis of <10 days duration of suspected microcrystalline origin between October 2012 and January 2014 were prospectively included in the study. Aspiration of the symptomatic joint was performed and crystals identified by polarizing light microscopy. All patients underwent an US of the symptomatic joint as well as both knees, ankles and 1^stMTP joints that was performed by a rheumatologist who was “blinded” to the clinical history within 24 hours of joint aspiration. An “US diagnosis” was made based of the findings in the symptomatic joint as well as the other joints examined by US.

Results

In 112 patients joint fluid was obtained. 53 had MSU, 27 CCPD and 9 had both crystals. No crystals were detected in 23. US signs of gout , CCP or mixed crystal  deposition were found in symptomatic joints of 40/38/7 patients respectively, and by multiple joints US, in 68/59/16  patients.

Table1 describes the sensitivity, the specificity, and the positive predictive value (PPV) and negative predictive values (NPV)

The sensitivity of US signs in the symptomatic joint for both gout and CCP is poor. US is more specific for the diagnosis of gout that CCP arthritis (PPV>90% against 60%).

By US of multiple joints, the sensitivity of US for both diagnoses rose significantly but the specificity and the PPV decreased, especially for CCP (PPV52%). In absence of US signs in all the joints, CCP arthritis is highly unlikely (NPV 87%).

Conclusion

In patients with a clinical suspicion of acute microcrystalline arthritis, US examination may be of assistance in the diagnosis if joint aspiration is not feasible. The examination of multiple joints is required to obtain the best clinical utility

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/performance-of-joint-ultrasonography-in-the-diagnosis-of-suspected-acute-crystal-arthritis-results-of-a-prospective-study-of-112-patients/