A New Era for Calcium Pyrophosphate Deposition Disease Research: The First-Ever Calcium Pyrophosphate Deposition Disease Classification Criteria and Considerations for Measuring Outcomes in Calcium Pyrophosphate Deposition Disease

Calcium pyrophosphate deposition (CPPD) disease is a crystalline arthritis that was described more than 60 years ago, yet our knowledge about this condition greatly lags behind other forms of arthritis. This is an exciting era for CPPD disease as a robust framework for CPPD clinical research has been established. The American College of Rheumatology (ACR) and EULAR co-sponsored the development of the first-ever classification criteria for CPPD. The Outcomes Measures in Rheumatology (OMERACT) CPPD Ultrasound Subtask Force developed and validated definitions for ultrasonographic findings of CPPD, and the OMERACT CPPD Working Group is establishing a core outcome domain set for this crystalline arthritis. This review focuses on key elements of the 2023 ACR/EULAR CPPD disease classification criteria and considerations for measuring outcomes in CPPD disease.