Comparison of ultrasonography and radiography of the wrist for diagnosis of calcium pyrophosphate deposition.

OBJECTIVE: Ultrasound (US) seems a useful tool for diagnosis of calcium pyrophosphate (CPP) deposition (CPPD). We aimed to compare the performance of US and conventional radiography of the wrist for diagnosis of CPPD.

METHODS: Patients with CPP crystals identified in synovial fluid (SF) (knee, hip, shoulder, ankle or wrist) were consecutively included and compared to patients without CPP crystals in synovial fluid considered as controls. As recommended, we used the term chondrocalcinosis (CC) to assess imaging features suggesting CPPD. In all patients, US and radiographic assessment of CC of the wrists was performed by two distinct operators blinded each other (one operator by imaging modality). The two operators were blinded to clinical data, SF analysis and US or radiography findings.

RESULTS: We included 32 CPPD patients and 26 controls. Among CPPD patients, US revealed CC in 30 (93.7%) and radiography in 17 (53.1%) (P<0.001). The sensitivity and specificity of US for the diagnosis of CPPD were 94% and 85%, respectively; the positive likelihood ratio (LR+) was 6.1. The sensitivity and specificity of radiography were 53.1% and 100%, respectively. At joints level independently of SF analysis, US revealed CC in 35 joints without radiographic CC whereas X-rays showed CC in 3 joints without US CC. The κ coefficient between US and radiography for CC was moderate: 0.33 (0.171-0.408).

CONCLUSION: Our study suggests that wrist US should be considered as a relevant tool for the diagnosis of CPPD, with higher sensitivity than radiography for detecting CPP deposits.