Sensitivity and Reproducibility of Ultrasonography in Calcium Pyrophosphate Crystal Deposition in Knee Cartilage: A Cross-sectional Study.

OBJECTIVE: To compare the ability to detect calcium pyrophosphate (CPP) crystals deposition (CPPD) in knee cartilage by ultrasonography (US) and radiography. METHODS: Patients with knee effusion were consecutively included and underwent radiography and US evaluation of knees. Diagnosis of CPPD was made by the identification of CPP crystals. Two blinded rheumatologists performed US assessment. RESULTS: We included 51 patients (25 with CPPD). US revealed hyperechoic spots in all 25 patients with CPPD (sensitivity 100%, specificity 92.3%), whereas radiography revealed CPPD in 16 (sensitivity 64%, specificity 100%; p < 0.0001). CONCLUSION: US of knees is more sensitive than radiography for CPPD diagnosis.

Ultrasound in gout: a useful tool for following urate-lowering therapy.

OBJECTIVE: We aimed to determine the ability of ultrasonography (US) to show decrease or disappearance of urate deposits in gouty patients requiring urate-lowering therapy (ULT). METHODS: To be included in this prospective single-centre study, patients needed toexhibit (1) proven gout by monosodic urate (MSU) crystals in synovial fluid and (2) US-evidenced urate deposits (double contour [DC] sign and/or tophi) before starting ULT (allopurinol [n=4], febuxostat [n=12]). At baseline and after six months of ULT, one trained ultrasonographer assessed the knee and first metatarsophalangeal (MTP1s) joints. Serum uric-acid (SUA) level was assessed at baseline and at three and six months after ULT initiation. Correlation between US findings and achievement of SUA level objective (< 360µmol/L) was estimated by the kappa coefficient (κ). RESULTS: We studied 16 patients (all males, mean age 61.0±18.3 years). The mean disease duration was 7.1±6.2 years. Tophi were found at clinical examination in 56% of patients. Baseline SUA levels were 688±153µmol/L. At baseline, US revealed tophi or a DC sign among 62.5 to 75% of patients in knees and 87.5% in MTP1s. After six months of ULT, none of the four patients, not achieving the SUA level objective, had disappearance of US features. Among the remaining 12 patients, US features (tophi or DC sign) disappeared or decreased in all but one with a stable DC sign in one MTP1. The correlation between the whole US examination and SUA level was excellent (κ=0.875). CONCLUSIONS: US could show disappearance of urate deposits after ULT and appears to be well correlated with efficacy of ULT.