Background The Calcium Pyrophosphate Deposition Disease (CPPD) is a disease frequently observed in the clinical practice but currently its exact prevalence is unknown. In fact, the data available in the literature vary depending on method used, generally x-ray or synovial fluid analysis, while no studies evaluated the ultrasound (US) prevalence of Calcium Pyrophosphate (CPP)deposits.

Objectives The evaluation of the prevalence of CPP deposits in a cohort of patients (pt) that undergo US examination of wrists and knees.

Methods We extracted from our database all reports of pt undergoing US exam of wrists and knees, referred to our outpatient clinic from October 2005 to January 2015. All US exams were performed by rheumatologists expert in muscoloskeletal ultrasound (MSUS) using an Esaote MyLab70 equipped with a 4–13 MHz linear probe. We recorded the presence of CPP deposits at the medial meniscus (MM), the lateral meniscus (LM) and the hyaline cartilage (HC) in the knees and at the triangular fibrocartilage (TF) of the wrists. Statistical analysis was performed with SPSS.

Results US reports of 984 pt (81,9% female, mean age 50,28 SD±17,22) were included in this study. The overall prevalence of CPP deposits was 6,6% (65/984pt). In this group, the CPP deposits were observed in the 32,3% (21/65pt) of the wrists (bilaterally 61,9%) and in the 93,8% (61/65pt)of the knees (bilaterally 67,21%). The involvement of both joints were observed in the 26,15% (17/65pt).

Analysing the prevalence by ages, it was 2,1% (14/664pt) in pt under 60 years old (yo), while it increased to 16,7% (51/306pt) in pt over 60. The prevalence was 8,7% (16/184pt) between 60 and 70 yo, 26,7% (24/90pt) between 70 and 80 yo, and increased to 34,4% (11/32pt) in pt over 80.

Regarding the different joint structures, the prevalence was 89,2% (58/65pt) in menisci, (83,1% MM, 78,5% LM) and 32,3% (21/65pt) in the HC. The TF was involved in 32,3% of cases (21/65pt). Thus, according to previous studies¹, our results showed that menisci, particularly MM, are the most involved by CPPD, appearing as the favorite site for US identification of CPP deposits. Moreover, this study confirmed the correlation between the aging and the increased prevalence of CPP deposits. However, our analysis showed a higher prevalence respect to the values obtained in previous studies that considered the x-ray as the reference method². However, this trend should be further confirmed with a prospective assessment conducted in a larger sample of patients.

Conclusions To our knowledge this is the first attempt to define the CPPD prevalence with US, that recently entered in EULAR recommendations as a promising diagnostic tool for CPPD³. Considering its accuracy, non-invasiveness and low cost, the US could be widely used for CPPD diagnosis also for large scale evaluation, planned in order to define the prevalence of this disease.

1. Filippou G et al Extent and distribution of CPP deposits in patients affected by calcium pyrophosphate dihydrate deposition disease: an ultrasonographic study. Ann Rheum Dis 2013

2. Ciancio G et al Epidemiology of gout and chondrocalcinosis. Reumatismo 2011

3. Zhang W et al European League Against Rheumatism recommendations for calcium pyrophosphate deposition. Part I: terminology and diagnosis. Ann Rheum Dis 2011

Disclosure of Interest None declared