Gout Diagnosis and Joint Aspiration

Indications for Joint Aspiration

The European League Against Rheumatism (EULAR) recommends that joint aspiration and crystal examination should be performed in all undiagnosed inflammatory arthritis cases, with a high level of agreement (8.8±0.3) 1
Joint aspiration is mandatory in cases of suspected septic arthritis, as clinical algorithms are not validated to rule out septic arthritis, and gout and infection can coexist 2, 3
The American College of Physicians suggests that joint aspiration for Gram stain and culture is an essential part of diagnostic workup in suspected septic arthritis 4

The EULAR proposes a stepped diagnostic approach: (1) crystal search, (2) clinical diagnosis if joint aspiration is not feasible, and (3) imaging if clinical diagnosis is uncertain and crystal identification is lacking, with a recommendation strength of 8.6±1.0 for crystal search and 8.5±1.0 for imaging 1
Clinical algorithms, such as the CGD criteria and Janssens' rule, have sensitivities and specificities above 80% for early gout, particularly in patients with recent onset attacks, but may overlook other conditions with similar presentation, such as septic arthritis 4, 8

If joint aspiration is not possible, ultrasound, DECT, and conventional radiography can be used as diagnostic alternatives, with ultrasound having a pooled sensitivity of 74% and specificity of 88% for the "double-contour sign" 8, 9
DECT has a sensitivity of 85-100% and specificity of 83-92%, but is less sensitive for early gout 8, 9

Experienced examiners can achieve sensitivities of 63-78% and specificities of 93-100% for MSU analysis, but the sensitivity is limited in early gout 4, 9
The risk of complications is low, with severe complications occurring in 0.1% of cases and mild complications in 1.4% of cases, mostly mild pain after the procedure 2, 5, 9

Hyperuricemia alone is not diagnostic, as many hyperuricemic patients never develop gout, and acute gout attacks can occur with normal uric acid levels 1, 7
Delayed diagnosis due to delayed joint aspiration can lead to longer hospitalizations 9
Misdiagnoses can occur with both joint aspiration and diagnostic algorithms 4