Based on the Outcome Measures in Rheumatology (OMERACT) definition, ultrasound demonstrated excellent reliability and better diagnostic capacity than conventional radiology in calcium pyrophosphate deposition (CPPD) disease, according to results of a prospective, single-center study published in Osteoarthritis and Cartilage.

The investigators included patients with knee effusion who underwent synovial fluid (SF) analysis. They performed SF aspiration in patients with monoarthritis (chronic or acute), suspicion of crystal-induced arthritis or joint infection, or monoarthritis in those with chronic polyarthritis. All participants (43 individuals with CPPD crystals in SF and 131 controls) were recruited over a 2-year period. The diagnostic performance of ultrasound for CPPD was explored at the level of menisci (medial meniscus and lateral meniscus), hyaline cartilage, tendons, and SF of the knee, along with an evaluation of interobserver and intraobserver reliability.

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Ultrasound identified CPPD in menisci, hyaline cartilage, and tendons significantly more often among patients with CPPD compared with controls (P <.0001). The presence of ultrasound CPP deposits in SF, however, did not differ significantly between the 2 groups. Combined ultrasound assessment of the 3 components — menisci, hyaline cartilage, and tendons — demonstrated the best diagnostic value. The sensitivity and specificity for ultrasound evaluation of the 3 components were 74.4% and 77.1%, respectively; in contrast, for conventional radiography assessment, the sensitivity and specificity were 44.2% and 96.9%, respectively.

Interobserver and intraobserver reliability were excellent for medial meniscus (κ=0.930) and lateral meniscus (κ=0.905). Moreover, the kappa values for hyaline cartilage (κ=0.844) and SF (κ=0.817) also demonstrated excellent agreement. Interobserver reliability for overall tendons (quadriceps and/or patellar tendons), quadriceps tendon, and patellar tendon, however, demonstrated the lowest agreement (κ=0.532, κ=0.382, and κ=0.658, respectively). Additionally, intraobserver agreement was excellent for medial meniscus (κ=0.972), lateral meniscus (κ=0.942), hyaline cartilage (κ=0.957), quadriceps tendon ((κ=0.828), patellar tendon (κ=0.886), and SF (κ=0.925). Although intraobserver reliability for overall tendons was also good, it was associated with the lowest agreement (κ=0.788).

The investigators concluded that the combined assessment of menisci, hyaline cartilage, and tendons demonstrated the best diagnostic performance at the knee level. Evaluation of only hyperechoic deposits within the SF could lead to overdiagnosis of CPPD. Ultrasound and conventional radiography appear to be complementary diagnostic examinations for patients with CPPD, taking into account the high sensitivity of ultrasound and the high specificity of conventional radiography.

Reference

Lee K-A, Lee S-H, Kim H-R. Diagnostic value of ultrasound in calcium pyrophosphate deposition disease of the knee joint [published online February 6, 2019]. Osteoarthritis Cartilage. doi:10.1016/j.joca.2018.11.013