Reliability and Diagnostic Accuracy of Radiography for the Diagnosis of Calcium Pyrophosphate Deposition: Performance of the Novel Definitions Developed by an International Multidisciplinary Working Group.

OBJECTIVE: To assess the reliability and diagnostic accuracy of new radiographic imaging definitions developed by an international multidisciplinary working group for identification of calcium pyrophosphate deposition (CPPD). METHODS: Patients with knee osteoarthritis scheduled for knee replacement were enrolled. Two radiologists and 2 rheumatologists twice assessed radiographic images for presence or absence of CPPD in menisci, hyaline cartilage, tendons, joint capsule, or synovial membrane, using the new definitions. In case of disagreement, a consensus decision was made and considered for the assessment of diagnostic performance. Histologic examination of postsurgical specimens under compensated polarized light microscopy was the reference standard. Prevalence-adjusted bias-adjusted kappa values were used to assess reliability, and diagnostic performance statistics were calculated. RESULTS: Sixty-seven patients were enrolled for the reliability study. The interobserver reliability was substantial in most of the assessed structures when considering all 4 readers (κ range 0.59-0.90), substantial to almost perfect among radiologists (κ range 0.70-0.91), and moderate to almost perfect among rheumatologists (κ range 0.46-0.88). The intraobserver reliability was substantial to almost perfect for all the observers (κ range 0.70-1). Fifty-one patients were included in the accuracy study. Radiography demonstrated an overall specificity of 92% for CPPD, but sensitivity remained low for all sites and for the overall diagnosis (54%). CONCLUSION: The new radiographic definitions of CPPD are highly specific against the gold standard of histologic diagnosis. When the described radiographic findings are present, these definitions allow for a definitive diagnosis of CPPD, rather than other calcium-containing crystal depositions; however, a negative radiographic finding does not exclude the diagnosis.

Development and validation of an OMERACT ultrasound scoring system for the extent of calcium pyrophosphate crystal deposition at the joint level and patient level.

BACKGROUND: The Calcium Pyrophosphate Deposition (CPPD) subgroup of the Outcome Measures in Rheumatology (OMERACT) Ultrasound working group was established to validate ultrasound as an outcome measure instrument for CPPD, and in 2017 has developed and validated standardised definitions for elementary lesions for the detection of calcium pyrophosphate crystals in joints. The aim of this study was to develop and evaluate the reliability of a consensus-based ultrasound scoring system for CPPD extent, representing the next phase in the OMERACT methodology. METHODS: In this study the novel scoring system for CPPD was developed through a stepwise process, following an established OMERACT ultrasound methodology. Following a previous systematic review to gather available evidence on existing scoring systems for CPPD, the novel scoring system was developed through a Delphi survey based on the expert opinion of the members of the OMERACT Ultrasound working group-CPPD subgroup. The reliability of the scoring system was then tested on a web-based and patient-based exercise. Intra-reader and inter-reader reliability of the new scoring system was assessed using weighted Light's κ coefficients. FINDINGS: The four-grade semiquantitative scoring system consisted of: grade 0 (no findings consistent with CPPD), grade 1 (≤3 single spots or 1 small deposit), grade 2 (>3 single spots or >1 small deposit or ≥1 larger deposit occupying ≤50% of the structure under examination in the reference image-ie, the scanning view with the highest grade of depositions), and grade 3 (deposits that occupy more than 50% of the structure under examination in the reference image). The score should be applied to the knee (menisci and hyaline cartilage) and the triangular fibrocartilage complex of the wrist. The intra-reader and inter-reader reliabilities on static images were almost perfect (κ 0·90 [95% CI 0·79-1·00] and κ 0·84 [0·79-0·88]), and on the eight patients recruited (four [50%] female and four [50%] male) were substantial (κ 0·72 [95% CI 0·47 to 0·96] and 0·66 [0·61 to 0·71]). INTERPRETATION: This OMERACT ultrasound scoring system for CPPD was reliable on both static images and patients. The scoring system might be a valuable tool for ensuring valid and comparable results in clinical trials and could help monitor the extent of crystal deposition in patients with CPPD in clinical practice. FUNDING: The Italian Ministry of Health - Ricerca Corrente.

Criterion validity of ultrasound in the identification of calcium pyrophosphate crystal deposits at the knee: an OMERACT ultrasound study.

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.