OP0152 DIAGNOSTIC PERFORMANCE OF HIP ULTRASOUND IN CALCIUM PYROPHOSPHATE DEPOSITION DISEASE

Abstract

BackgroundCalcium Pyrophosphate Deposition Disease (CPPD) is a chronic and potentially incapacitating disease. The reference standard for its diagnosis is the identification of calcium pyrophosphate (CPP) crystals in synovial fluid. Ultrasound (US) has been proven to be a high-sensibility and specificity tool for diagnosing CPPD. Still, its diagnostic performance for hip joint involvement has yet to be determined.ObjectivesTo evaluate the diagnostic performance of US compared with synovial fluid analysis and histopathology (hyaline cartilage, fibrocartilage, synovial membrane) for the identification of hip CPP deposits.MethodsWe included patients older than 50 years with osteoarthritis programmed for hip replacement surgery in a tertiary referral hospital. Patients with an inflammatory or autoimmune rheumatologic disease were excluded. A pre-surgical US of the affected hip was performed with a LOGIQTMe device and a convex transducer (2-5 MHz); the anatomical structures evaluated were the acetabular fibrocartilage (FC) and the hyaline cartilage of the femoral head (HC), video tracking was recorded and a dichotomic score was assigned to determine the presence or absence of CPP deposits (in line with OMERACT definitions). During surgery, a sample of hip synovial fluid was obtained and examined using polarized light microscopy. After surgery, an experimented pathologist examined the FC and HC for CPP crystals.ResultsOne hundred patients were included. 54% women with a mean age of 64.8±8.5 years. All patients had advanced osteoarthritis (Kellgren-Lawrence 3 = 33 and Kellgren-Lawrence 4=67; Tönnis 2= 34 and Tönnis 6= 66). A frequency of 62% CPP deposits was found through US examination, of which 19.4% were found on FC, 46.8% on HC, and 33.8% in both. Regarding pathology evaluation, a prevalence of 61% of CPP crystals was found; 13.1% were found on FC, 9.8% were found on HC, and 77.1% were found in both. 33% of patients had synovial effusion and 9% had synovial hypertrophy. Synovial fluid was obtained in 62% of patients, with a median volume of 0.8mL (IQR 0.5-1.5mL), and CPP crystals were found in 19.4% (12/62) of samples. Chondrocalcinosis in XR was found in 10%. A sensitivity of 90% and a specificity of 82% were obtained, the positive predictive value was 89%, and the negative predictive value was 84%. The area under the curve for the US compared with histopathology for the diagnosis of hip CPPD was 0.86 (CI 95% 0.78-0.94) (Figure 1).ConclusionUS is a valid imaging method with good diagnostic performance for diagnosing CPPD in the hip joint.Reference[1] Filippou G. Ann Rheum Dis 2021;80(2):261–7.Figure 1.ROC curve of USAcknowledgements:NIL.Disclosure of InterestsNone Declared.