SAT0510 Ultrasound versus Synovial Fluid Analysis for the Diagnosis of Calcium Pyrophosphate Dihydrate Deposition Disease: is IT Cppd? Ask Us!

Abstract

Background The diagnosis of calcium pyrophosphate crystal (CPP) deposition disease (CPPD) is mainly based on the synovial fluid analysis and Xrays. US has demonstrated high sensitivity and specificity values for diagnosing CPPD compared to synovial fluid analysis as the gold standard (1), but less is known about sensitivity and specificity of synovial fluid analysis itself. Objectives to compare ultrasonography and synovial fluid analysis performances in the diagnosis of CPPD using a real gold standard. Methods We enrolled in our study all patients waiting to undergo knee replacement surgery due to severe osteoarthritis. Each patient underwent US examination of the knee, focusing on the menisci and the hyaline cartilage, the day prior to surgery, scoring each site according to the presence/absence of CPP as defined previously (1). The day of the surgery, synovial fluid of the knee (if present) was aspirated by the surgeon. After surgery, the menisci, condyles and the synovial fluid were retrieved and examined microscopically. Synovial fluid analysis was performed on wet preparations. For the meniscus and cartilage microscopic analysis, six samples were collected, either from the surface and from the internal of the structure trying to cover a large part of it. All slides were observed under transmitted light microscopy and by compensated polarised microscopy. A dichotomous score was given for the presence/absence of CPP. US and microscopic analysis were performed by different operators, blind to each other's findings. Sensitivity and specificity of US and synovial fluid were calculated using microscopic findings of the menisci and cartilage as the gold standard. Results we enrolled in the study 32 patients (9 males), mean age of 74 years old (±7). Synovial fluid has been collected from 24 patients. If we consider all the structures examined with US (both menisci and cartilage of both condyles), were positive for CPP 22 patients while synovial fluid analysis was positive for 11 patients. At microscopic examination of the speciments, 21 patients were positive for CPP in at least one of the structures examined. US demonstrated a sensitivity of 95% (CI95: ±0.01) with PPV =0.91 and specificity of 81% (CI95: ±0.23) and a NPV =0.90 while respective values for synovial fluid microscopic analysis were 73% (CI95: ±0.22) with PPV of 1 and 100% (CI95: ±0) with NPV of 0.69. Conclusions US demonstrated higher sensitivity values for identifying CPP deposits in the knee joint than synovial fluid analysis. Specificity values on the other had were higher for the microscopic analysis as expected. Globally we believe that for its intrinsic characteristics, the non invasive nature, for the high values of both specificity and specificity, and last but not least, for the capability to address differential diagnosis US should be the first exam ti be performed when CPPD disease is suspected. As this study demonstrates, the presence of CPP crystals in the synovial fluid, definitely confirms the diagnosis but a negative microscopi...

Ultrasound in the diagnosis of calcium pyrophosphate dihydrate deposition disease. A systematic literature review and a meta-analysis

“…Regarding the evaluation of US diagnostic accuracy in CPPD, only 13 studies had enough data for constructing the contingency tables but in one of these 4e6, 8,10,22,30,31,34,35,41,43 , only sensitivity could be calculated 21 .…”

“…In all the selected studies but five 8,22,31,35,43 the data were suitable for defining US sensitivity and specificity only at the level of a single joint structure (i.e., cartilage, fibrocartilage, tendon) and not at the level of the whole joint or patient.…”

“…For the studies considering the whole patient and not a single structure 8,22,31,35,43 , sensitivity and specificity ranged from 0.60 to 1.00 and from 0.88 to 1, respectively. The pooled sensitivity was 0.89 (95% CI 0.72e0.97) and specificity was 0.94 (95% CI 0.87e0.98).…”

“…Considering the US performance at the level of each joint structure, the highest value of sensitivity was obtained at the hyaline cartilage 4,5,10,21,35,41,43 with a pooled sensitivity of 0.77 (95% CI 0.63e0.87) and specificity of 0.92 (0.16e1.00), and at the fibrocartilage 4,34,35,41,43 with a pooled sensitivity of 0.77 (95% CI 0.31e0.96) and specificity of 0.96 (95% CI 0.75e1.00), while for the tendons 6,30 the sensitivity and specificity were respectively 0.34 (0.16e0.58) and 1.00 (95% CI 0.89e1.00).…”

Identification of calcium pyrophosphate deposition disease (CPPD) by ultrasound: reliability of the OMERACT definitions in an extended set of joints—an international multiobserver study by the OMERACT Calcium Pyrophosphate Deposition Disease Ultrasound Subtask Force

“…Considering this aspect, one could also stipulate that the prevalence of CPPD is also underestimated because only patients with symptoms undergo these two diagnostic exams and a large proportion of our elderly population present the asymptomatic form and are never diagnosed. Furthermore, X-rays have been demonstrated to have a low sensitivity for the identification of CPP deposition,5 while synovial fluid analysis is not always performed, and CPP crystal are often missed contributing to the underdiagnosis.…”