Prevalence of calcium pyrophosphate and monosodium urate crystals in synovial fluid of patients with previously diagnosed joint diseases

AbstractSynovial fluid (SF) leukocytes can be counted microscopically in a Neubauer chamber or by automated procedures using haematology analysers. Knowledge of laboratory artefacts is crucial for the correct interpretation of results obtained using automated methods. SF pseudoeosinophilia has recently been described as a new artefact in patients with crystal-related arthropathies. We investigated whether pseudoeosinophilia of SF is restricted to crystal-related disorders, or if it may also occur in other arthropathies.We compared the percentages of eosinophils in 120 crystal containing SF samples with 185 crystal-free specimens using the Wilcoxon test. Crystal positive samples, determined by polarised microscopy, contained at least two monosodium urate or calcium pyrophosphate crystals per 10 high power fields (630× magnification). True SF eosinophilia was ruled out by microscopic examination of stained slides.Crystal positive samples had significantly higher percentages of eosinophils than the controls (p<0.0001). No significant differences between the two crystal types were found (p=0.693). Thus, pseudoeosinophilia was significantly correlated with the presence of crystals, and none of the distinct crystal types was more likely to be associated with pseudoeosinophilia.In this study, SF pseudoeosinophilia was confirmed as a crystal-related laboratory artefact which has to be considered in the interpretation of automated SF leukocyte differential counts.

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Coincidence of calcium pyrophosphate and monosodium urate crystals in the synovial fluid of patients with gout determined by the cytocentrifugation technique: Table 1

Annals of the Rheumatic Diseases ◽

10.1136/ard.2010.136721 ◽

2010 ◽

Vol 70 (6) ◽

pp. 1163-1164 ◽

Cited By ~ 23

Author(s):

C Robier ◽

M Neubauer ◽

F Quehenberger ◽

F Rainer

Keyword(s):

Synovial Fluid ◽

Calcium Pyrophosphate ◽

Monosodium Urate ◽

Monosodium Urate Crystals ◽

Urate Crystals

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Dual energy CT findings in gout with rapid kilovoltage-switching source with gemstone scintillator detector

BMC Rheumatology ◽

10.1186/s41927-019-0104-5 ◽

2020 ◽

Vol 4 (1) ◽

Author(s):

Elin Svensson ◽

Ylva Aurell ◽

Lennart T. H. Jacobsson ◽

Anton Landgren ◽

Valgerdur Sigurdardottir ◽

...

Keyword(s):

Synovial Fluid ◽

Dual Energy ◽

University Hospital ◽

Dual Energy Ct ◽

Kappa Statistics ◽

Monosodium Urate ◽

Beam Hardening ◽

Monosodium Urate Crystals ◽

Scintillator Detector ◽

Urate Crystals

Abstract Background A definite diagnosis of gout requires demonstration of monosodium urate crystals in synovial fluid or in tophi, which in clinical practice today seldom is done. Dual energy CT (DECT) has repeatedly been shown to be able to detect monosodium urate crystals in tissues, hence being an alternative method to synovial fluid microscopy. The vast majority of these studies were performed with CT scanners with two X-ray tubes. In the present study we aim to investigate if and at what locations DECT with rapid kilovoltage-switching source with gemstone scintillator detector (GSI) can identify MSU crystals in patients with clinically diagnosed gout. We also performed a reliability study between two independent readings. Methods Patients with new or established gout who had been examined with DECT GSI scanning of the feet at Sahlgrenska University Hospital, Mölndal between 2015 and 2018 were identified. Their medical records were sought for gout disease characteristics using a structured protocol. Urate deposits in MTP1, MTP 2–5, ankle/midfoot joints and tendons were scored semiquantatively in both feet and presence of artifacts in nail and skin as well as beam hardening and noise were recorded. Two radiologists performed two combined readings and scoring of the images, thus consensus was reached over the scoring at each occasion (Espeland et al., BMC Med Imaging. 2013;13:4). The two readings were compared with kappa statistics. Results DECT GSI could identify urate deposits in the feet of all 55 participants with gout. Deposits were identified in the MTP-joints of all subjects but were also present in ankle/midfoot joints and tendons in 96 and 75% respectively. Deposition of urate was predicted by longer disease duration (Spearman’s Rho 0.64, p < .0001) and presence of tophi (p = 0.0005). Artifacts were common and mostly found in the nails (73%), a minority displayed skin artifacts (31%) while beam hardening and noise was rare. The agreement between the two readings was good (Κ = 0.66, 95% CI = 0.61–0.71). Conclusion The validity of DECT GSI in gout is supported by the identification of urate in all patients with clinical gout and the good correlations with clinical characteristics. The occurrence of artifacts was relatively low with expected locations.

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