Background In the last years, the role of Ultrasound (US) for the diagnosis of calcium pyrophosphate deposition disease (CPPD) has been extensively growing. However, some issues have still to be resolved, being one of the most important the heterogeneity of the criteria used for the identification of calcium pyrophosphate crystals (CPP) deposits.
Objectives The aim of this study was to define the US elementary lesions in CPPD
Methods The panel of experts was compound by 18 members of the Omeract US group, especially interested in microcrystalline arthritides.
The first step was a systematic literature review aimed to select the studies regarding US and CPPD in order to collect all the definitions about US elementary findings in CPPD. The definitions retrieved by the literature were used for drawing up a first group of propositions. The experts evaluated these definitions, adding any further preposition according to their experience that could improve the initial set. According to the systematic review, the propositions about US elementary lesions were divided by anatomical structure: fibrocartilage, hyaline cartilage, tendons and synovial fluid. For each structure were defined: shape, echogenicity, localization and behaviour at dynamic scanning.
In the next rounds, the experts voted their level of agreement for each proposition according to the Likert scale (1 strongly disagree 5:strongly agree) with the possibility to add comments. After each round, a facilitator modified the prepositions according to the comments received. The consensus for each preposition was considered achieved if the agreement was equal or more than 75%
Results Three Delphi rounds were necessary in order to reach agreement. After the first round, 20 of the 93 definitions retrieved by the literature reached the consensus. During the second one, 23 propositions achieved the agreement while, after the last Delphi round, the number of propositions increased to 27. All the members responded to all the phases of the survey.
Final definitions for US identification of CPPD are illustrated in Table 1
Conclusions To our knowledge this is the first set of definitions for US identification of CPPD created according to a consensus procedure between experts. These definitions should help sonographers to classify correctly patients with suspected CPPD thus giving the possibility to organise multicentre studies. However, the reliability and the diagnostic accuracy of this set has to be assessed before they become integral part of the daily clinical practice
Disclosure of Interest None declared