THU0420 ULTRASOUND SHOWS GREAT ACCURACY FOR THE DIAGNOSIS OF CRYSTAL ARTHRITIS IN PATIENTS WITH RECENT-ONSET SYNOVITIS

Abstract

Background:The value of ultrasound (US) in the diagnosis of crystal arthropathy, such as gout or calcium pyrophosphate deposition disease (CPPD), in patients with recent onset synovitis has been evaluated only by a few studies.Objectives:To investigate, in patients with acute arthritis, the accuracy of US for the diagnosis of crystal arthropathy.Methods:Consecutive patients with recent onset (<6 weeks) acute arthritis were enrolled. The US examinations were performed a rheumatologist blinded to clinical data. Calcium pyrophosphate and monosodium urate crystal deposits were identified in the joint affected by synovitis (target joint), as well as in the classic sites for gout and CPPD (set of joint) (Table 1), according to the OMERACT definitions.Table 1.Anatomical targets of ultrasound examinationGoutCPPDBothWristRadiocarpal jIntercarpal jTriangular FC complexScapho-lunate ligament/HandDC in the II MCPj HCDeposits within the II MCPj HCII MCPjKneePopliteal grooveDC in the femoral condyle’s HCMeniscal FCDeposits within the femoral condyles’ HCSupra-patellar recessesHipDC in the femoral head’s HCDeposits within the femoral head’s HCAcetabular FCHip jFootDC in the I MTPj HCDeposits within I MTPj HCI MTPjLegend.DC: double contour,FC: fibrocartilage,HC: hyaline cartilage,MCPj: metacarpophalangeal joint,MTPj: metatarsophalangeal joint,j: joint.Table 2.Diagnostic accuracy of US and SFASensitivitySpecificityPositive LHRNegative LHRUS (target joint)Crystal arthritis0.84(0.7-0.93)0.91(0.8-0.97)9.5(4.1-22)0.2(0.1-0.3)CPPD0.91(0.71-0.99)0.91(0.80-0.97)10.2(4.4-23.8)0.1(0-0.4)Gout0.83(0.61-0.97)0.91(0.80-0.97)9.1(3.9-21.4)0.2(0.1-0.5)US (set of joints)Crystal arthritis0.96(0.85-0.99)0.87(0.76-0.95)7.6(3.8-15.3)0.1(0-0.2)CPPD1(0.85-1)0.88(0.76-0.95)8(4-16)0(0-0.2)Gout0.91(0.72-0.99)0.88(0.76-0.95)7.3(3.6-14.8)0.1(0-0.4)SFACrystal arthritis0.9(0.77-0.97)1(0.94-1)/0.1(0-0.2)CPPD0.90(0.7-0.99)1.0(0.94-1)/0.1(0-0.3)Gout0.91(0.71-0.99)1(0.94-1)/0.1(0-0.3)Legend.LHR: likelihood ratioSFA was performed in 67 knees (64.4%), 10 wrists (9.6%), 10 ankles (9.6%), 5 I MTP joints (4.8%), 5 hips (4.8%), 4 elbows (3.8%), 4 shoulders (3.8%).The total agreement between US and SFA was excellent (93.8% in CPPD and 90.2% in gout). SFA positive/US negative results occurred in 1 patient with CPPD (1.2%) and in 4 patients with gout (4.9%). On the contrary, US positive/SFA negative results occurred in 4 patients with CPPD (4.9%) and in 4 patients with gout (4.9%).The diagnostic accuracy of US and synovial fluid analysis (SFA) was evaluated taking the classification criteria for gout and CPPD as gold standard (1,2). Moreover, the US and SFA results were compared in the joints in which the SFA was performed.Results:One-hundred and four patients were enrolled: 22 CPPD patients, 23 with gout and 59 disease controls. Table 2 reports the diagnostic accuracy of US and SFA, using the classification criteria as gold standard.Figure 1provides a pictorial evidence of the US appearance of crystal deposits. A: anterior suprapatellar transverse scan of the femoral condylar HC. HC calcifications (arrows) B: anterior longitudinal scan of the hip. FC calcification (asterisk) C: anterior longitudinal scan of the ankle. DC sign (void arrow) . D: dorsal longitudinal scan of distal interphalangeal joint. DC sign (void arrow).Conclusion:US is useful for the diagnosis of gout and CPPD in patients with acute synovitis. Extending the US evaluation to the joints which are most commonly involved in gout and in CPPD, other than those affected by synovitis, increases the sensitivity of US.