Objective To evaluate the discriminatory ability of ultrasound in calcium pyrophosphate deposition disease (CPPD), using microscopic analysis of menisci and knee hyaline cartilage (HC) as reference standard.
Methods Consecutive patients scheduled for knee replacement surgery, due to osteoarthritis (OA), were enrolled. Each patient underwent ultrasound examination of the menisci and HC of the knee, scoring each site for presence/absence of CPPD. Ultrasound signs of inflammation (effusion, synovial proliferation and power Doppler) were assessed semiquantitatively (0–3). The menisci and condyles, retrieved during surgery, were examined microscopically by optical light microscopy and by compensated polarised microscopy. CPPs were scored as present/absent in six different samples from the surface and from the internal part of menisci and cartilage. Ultrasound and microscopic analysis were performed by different operators, blinded to each other’s findings.
Results 11 researchers from seven countries participated in the study. Of 101 enrolled patients, 68 were included in the analysis. In 38 patients, the surgical specimens were insufficient. The overall diagnostic accuracy of ultrasound for CPPD was of 75%—sensitivity of 91% (range 71%–87% in single sites) and specificity of 59% (range 68%–92%). The best sensitivity and specificity were obtained by assessing in combination by ultrasound the medial meniscus and the medial condyle HC (88% and 76%, respectively). No differences were found between patients with and without CPPD regarding ultrasound signs of inflammation.
Conclusion Ultrasound demonstrated to be an accurate tool for discriminating CPPD. No differences were found between patents with OA alone and CPPD plus OA regarding inflammation.
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Handling editor Josef S Smolen
Contributors Substantial contributions in planning the work: all authors. Substantial contributions in conducting the work: GF, AS, AA, CT, DG, RL, EN, EC, GH-B, PZ, CMB, DKM, SM, ZW, FF, MG, CP, DCC, HG, VI, JMT, RP, LCRD, EF, EC, TS, CC, FAV, DG, GM, AI. Substantial contributions in reporting the work: all authors.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Patient consent for publication Not required.
Ethics approval The study was approved by the local Ethics Committee of the University of Ferrara (principal investigator site, study number 171190 approved on 17 December 2017) and subsequently by local ethics committees of all the participating centres.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request. Data of the paper are deidentified participant data and are available upon request to the correspondent author.