THU0406 IDENTIFICATION OF INTRACELLULAR VACUOLES IN SYNOVIAL FLUID WITH CALCIUM PYROPHOSPHATE AND MONOSODIUM URATE CRYSTALS

Background:Synovial fluid analysis using polarized microscopy is the gold standard for the diagnosis of crystal-related arthritis. In our experience, we have noted that, when calcium pyrophosphate (CPP) crystals are observed, they sometimes appear within intracellular vacuoles. However, this phenomenon is not seen in those samples containing monosodium urate (MSU) crystals. This finding has been scantly reported in the literature, but may be useful in clinical practice to ensure accurate crystal identification.Objectives:Our study aims to assess whether the presence of vacuoles contributes to identifying the type of crystal, and also to gauge the frequency of their presentation.Methods:We conducted an observational study in a rheumatology unit between February and June of 2019. Synovial fluids containing CPP or MSU crystals, obtained in daily clinical practice, were consecutively included for analysis. Two observers simultaneously analyzed the presence of vacuoles by ordinary light and phase contrast microscopy in less than 24 hours after their extraction, using a microscope equipped with two viewing stations. The primary study variable was to determine whether CPP and MSU crystals are seen inside intracellular vacuoles, and to calculate the frequency of this finding for each type of crystal, estimating their 95% confidence interval (95% CI) and comparing rates using Fisher’s exact test.Results:Twenty-one samples were obtained. Data is given in the Table. MSU crystals were present in 7 (33.3%) and CPP crystals in 14 (66.6%). Interestingly, none of the MSU samples showed crystal-containing vacuoles (95% CI 0-35.4%). On the contrary, cytoplasmic vacuoles containing crystals were present in all of the CPP samples (95% CI 78.5-100%). The findings were confirmed by phase-contrast microscopy. Differences were statistically significant (p<0.001).Table.SAMPLES ACCORDING TO TYPE OF MICROCRYSTAL(n=21)SAMPLES WITH VACUOLS(UNDER ORDINARY LIGHT)SAMPLES WITH VACUOLS(UNDER PHASE CONTRAST)CPP (14; 66.6%)14 (100%)(95%CI 78.5-100%)14 (100%)(95%CI 78.5-100%)MSU (7; 33.3%)0 (0%)(95%CI 0-35.4%)0 (0%)(95%CI 0-35.4%)Conclusion:The presence of vacuoles may be a useful and easy way to differentiate MSU and CPP crystals when performing synovial fluid microscopy in clinical practice, since it appears to be a distinctive feature in CPP crystal fluids.References:[1]Kohn NN, Hughes RE, McCarty DJ Jr, Faires JS. The significance of calcium phosphate crystals in the synovial fluid of arthritic patients: the «pseudogout syndrome». II. Identification of crystals. Ann InternMed. 1962 May;56:738-45.[2]Pascual E, Sivera F, Andrés M. Synovial Fluid Analysis for Crystals. CurrOpRheumatol 2011;23:161-169.[3]McCarty DJ, Koopman WJ. Arthritis and allied conditions: A textbook of rheumatology, volumen 1. Lea &Febiger. 1993.[4]Pascual E, Sivera F. Synovial fluid crystal Analysis. En Gout and other crystal arthropathies. Terkeltaub R ed. Elsevier; 2012: p.20-34.[5]Hwang HS, Yang CM, Park SJ, Kim HA. Monosodium Urate Crystal-Induced Chondrocyte Death via Autophagic Process. Int J Mol Sci. 2015 Dec 8;16(12):29265-77.Image 1. Microscopy with ordinary light. Cells with cytoplasmic vacuoles are observed, as well as abundant intra and extracellular CPP crystals.Image 2. Microscopy with phase contrast technique. Cells with intracellular vacuoles are observed inside which have microcrystals with parallelepiped morphology, compatible with CPP.Disclosure of Interests: :None declared

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Persistence of Crystals in Stored Synovial Fluid Samples

The Journal of Rheumatology ◽

10.3899/jrheum.190468 ◽

2020 ◽

Vol 47 (9) ◽

pp. 1416-1423

Author(s):

Sonia Pastor ◽

José-Antonio Bernal ◽

Rocío Caño ◽

Silvia Gómez-Sabater ◽

Fernando Borras ◽

...

Keyword(s):

Synovial Fluid ◽

Light Microscopy ◽

Room Temperature ◽

Polarized Light ◽

Calcium Pyrophosphate ◽

Polarized Light Microscopy ◽

Tetraacetic Acid ◽

Monosodium Urate ◽

Prospective Longitudinal ◽

Msu Crystals

Objective.Lack of access to polarized light microscopy is often cited as an argument to justify the clinical diagnosis of crystal-related arthritis. We assessed the influence of time since sampling and preservation methods on crystal identification in synovial fluid (SF) samples under polarized light microscopy.Methods.This was a prospective, longitudinal, observational factorial study, analyzing 30 SF samples: 12 with monosodium urate (MSU) crystals and 18 with calcium pyrophosphate (CPP) crystals. Each SF sample was divided into 4 subsamples (120 subsamples in total). Two were stored in each type of preserving agent, heparin or ethylenediamine tetraacetic acid (EDTA), at room temperature or at 4°C. Samples were analyzed the following day (T1), at 3 days (T2), and at 7 days (T3) by simple polarized light microscopy, and the presence of crystals was recorded.Results.The identification of crystals in the MSU group was similar between groups, with crystals observed in 11/12 (91.7%) room temperature samples and in 12/12 (100%) refrigerated samples at T3. Identification of CPP crystals tended to decrease in all conditions, especially when preserved with EDTA at room temperature [12/18 (66.7%) at T3], while less reduction was seen in refrigerated heparin-containing tubes.Conclusion.Preserving samples with heparin in refrigerated conditions allows delayed microscopic examination for crystals. Avoiding crystal-proven diagnosis because of the immediate unavailability of microscopy no longer appears justified.

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AB0629 ACCURACY OF SYNOVIAL FLUID ANALYSIS FOR THE IDENTIFICATION OF CALCIUM PYROPHOSPHATE CRYSTALS: AN ANCILLARY STUDY OF OMERACT CRITERION VALIDITY STUDY FOR ULTRASOUND IN CPPD

Annals of the Rheumatic Diseases ◽

10.1136/annrheumdis-2021-eular.601 ◽

2021 ◽

Vol 80 (Suppl 1) ◽

pp. 1348.1-1348

Author(s):

A. Adinolfi ◽

S. Sirotti ◽

M. Gutierrez ◽

C. Pineda ◽

D. Clavijo Cornejo ◽

...

Keyword(s):

Synovial Fluid ◽

Diagnostic Accuracy ◽

Light Microscopy ◽

Hyaline Cartilage ◽

Microscopic Analysis ◽

Calcium Pyrophosphate ◽

Ancillary Study ◽

Fluid Analysis ◽

Synovial Fluid Analysis ◽

Sensitivity Specificity

Background:Synovial fluid analysis (SFA) via compensated polarized light microscopy is still considered the gold standard for the identification and diagnosis of Calcium Pyrophosphate Deposition disease (CPPD)-related arthropathies[1], but very few studies have been published about its diagnostic accuracy.Objectives:The aim of this study was to evaluate the accuracy of SFA in the identification of calcium pyrophosphate dihydrate (CPP) crystals compared to microscopic analysis of joint tissues as the reference standard.Methods:This is an ancillary study of an international, multicentre cross-sectional study performed by the CPPD subgroup of the OMERACT Ultrasound working group[2]. Consecutive patients with knee osteoarthritis (OA) waiting for total knee replacement surgery were enrolled in the study from 2 participating centres, Mexico and Romania. During surgical procedures synovial fluid (SF), menisci and hyaline cartilage were collected and analysed within 48 hours after surgery under transmitted light microscopy and compensated polarised light microscopy for the presence/absence of CPP crystals. All slides were analysed by expert examiners on site, blinded to other findings. A dichotomic score (absence/presence) was used for scoring both SF and tissues. Microscopic analysis of knee tissues was considered the gold standard. Sensitivity, specificity, accuracy, positive and negative predictive values (PPV and NPV) of SFA in the identification of CPP crystals were calculated.Results:15 patients (53% female, mean age 68yo ± 8.4) with OA of grade 3 or 4 according to Kellgren-Lawrence scoring were enrolled. 12 patients (80%) were positive for CPP crystals at SFA and 14 (93%) at tissues microscopic analysis. Among 12 SFA positive patients, all were positive for CPP crystals in either medial or lateral meniscus, and 11 were positive in both; 10 patients were positive at the hyaline cartilage, and all 10 were also positive for at least one meniscus. Regarding the 3 SFA negative patients, only one had no crystals in the examined tissues, while the other 2 patients had CPP crystals in both menisci and hyaline cartilage. The overall diagnostic accuracy of SFA compared to histology analysis for CPPD was 87%, with a sensitivity of 86% and a specificity of 100%, the PPV was 100% and the NPV was 33% (Table 1).Table 1.sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy of synovial fluid analysis compared to the reference standard. CI: Confidential Interval. SF: synovial fluid, in parentheses: numerators and denominators for all percentages provided.SensitivitySpecificityPPVNPVAccuracySF analysis86% (12/14)100% (1/1)100% (12/12)33% (1/3)87% (13/15)(0.65-0.99) CI 95%(0.0-0.25) CI 95%(0.65-0.99) CI 95%(0.0-0.25) CI 95%Conclusion:SFA demonstrated to be an accurate test for the identification of CPP crystals in patients with advanced OA. However, is not always feasible and carries some risks for the patient. Considering the availability of validated imaging techniques for the detection of CPPD, such as US, SFA could be used in those patients where imaging and clinical data are not definitely confirmatory of the disease.References:[1]W. Zhang et al., ‘European League Against Rheumatism recommendations for calcium pyrophosphate deposition. Part I: terminology and diagnosis’, Ann Rheum Dis, vol. 70, no. 4, pp. 563–570, Apr. 2011, doi: 10.1136/ard.2010.139105.[2]G. Filippou et al., ‘Criterion validity of ultrasound in the identification of calcium pyrophosphate crystal deposits at the knee: an OMERACT ultrasound study’, Ann Rheum Dis, p. annrheumdis-2020-217998, Sep. 2020, doi: 10.1136/annrheumdis-2020-217998.Disclosure of Interests:None declared.

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Hydroxyapatite Associated Disease in an Elderly Female: Differentiation from Aseptic Necrosis

Scottish Medical Journal ◽

10.1177/003693308903400208 ◽

1989 ◽

Vol 34 (2) ◽

pp. 438-439

Author(s):

D.F. Smith ◽

D.M. Reid

Keyword(s):

Clinical Practice ◽

Calcium Pyrophosphate ◽

Calcium Pyrophosphate Dihydrate ◽

Monosodium Urate ◽

Aseptic Necrosis ◽

Hydroxy Apatite ◽

Elderly Female ◽

Crystal Arthropathies ◽

Pyrophosphate Dihydrate ◽

Destructive Arthropathy

The crystal arthropathies caused by monosodium urate and calcium pyrophosphate dihydrate are commonly recognised, but the destructive arthropathy associated with the deposition of calcium hydroxy-apatite is less well known in general clinical practice.1 We describe a case with many of the classical features of hydroxy-apatite associated disease and discuss the features differentiating the condition from aseptic necrosis.

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Synovial Fluid Findings and Demographic Analysis of Patients With Coexistent Intra-articular Monosodium Urate and Calcium Pyrophosphate Crystals

JCR Journal of Clinical Rheumatology ◽

10.1097/rhu.0000000000000321 ◽

2016 ◽

Vol 22 (2) ◽

pp. 68-70 ◽

Cited By ~ 6

Author(s):

Emilia L. Heselden ◽

Antony J. Freemont

Keyword(s):

Synovial Fluid ◽

Calcium Pyrophosphate ◽

Demographic Analysis ◽

Monosodium Urate

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Laboratory investigations in gout

10.1093/med/9780199668847.003.0042 ◽

2016 ◽

Author(s):

Eliseo Pascual ◽

Francisca Sivera

Keyword(s):

Synovial Fluid ◽

Inflammatory Markers ◽

Serum Urate ◽

Calcium Pyrophosphate ◽

Monosodium Urate ◽

Renal Handling ◽

Cell Counts ◽

Laboratory Investigations ◽

Fluid Cell ◽

Methods Of Measurement

Gout is a consequence of hyperuricaemia and the treatment goal is to dissolve the crystals by reducing serum urate levels. The first section of this chapter focuses on laboratory investigations on gout, reviewing serum urate levels and its determinants, methods of measurement, and urate renal handling. Additionally it reviews the use of inflammatory markers and synovial fluid cell counts. The second section of the chapter deals with the identification of monosodium urate and calcium pyrophosphate crystals in synovial fluid. It reviews the use of an optic microscope fitted with polarized filters and an analyser. A clear step-by-step process with useful tips is provided.

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An Unusual Association: Iliopsoas Bursitis Related to Calcium Pyrophosphate Crystal Arthritis

Case Reports in Rheumatology ◽

10.1155/2015/935835 ◽

2015 ◽

Vol 2015 ◽

pp. 1-5 ◽

Cited By ~ 3

Author(s):

Marco Di Carlo ◽

Antonella Draghessi ◽

Marina Carotti ◽

Fausto Salaffi

Keyword(s):

Synovial Fluid ◽

Imaging Techniques ◽

Calcium Pyrophosphate ◽

Left Colectomy ◽

Fluid Analysis ◽

Unusual Association ◽

Hip Arthritis ◽

Synovial Fluid Analysis ◽

Crystal Arthritis ◽

Iliopsoas Bursitis

A 71-year-old man with osteoarthritis and chondrocalcinosis came to our observation developing a swelling in the groin region after a recent left colectomy for adenocarcinoma. The imaging techniques revealed the presence of an iliopsoas bursitis in connection with the hip. The synovial fluid analysis detected the presence of calcium pyrophosphate (CPP) crystals and allowed the final and unusual diagnosis of iliopsoas bursitis related to acute CPP crystal hip arthritis.

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Calcium pyrophosphate and monosodium urate crystals in synovial fluid as a cause of pseudoeosinophilia

Clinical Chemistry and Laboratory Medicine (CCLM) ◽

10.1515/cclm.2011.212 ◽

2011 ◽

Vol 49 (8) ◽

Cited By ~ 1

Author(s):

Christoph Robier ◽

Manfred Neubauer ◽

Franz Quehenberger ◽

Mariana Stettin ◽

Franz Rainer

Keyword(s):

Synovial Fluid ◽

Calcium Pyrophosphate ◽

Wilcoxon Test ◽

Correct Interpretation ◽

Monosodium Urate ◽

Monosodium Urate Crystals ◽

Automated Procedures ◽

Automated Methods ◽

Differential Counts ◽

Urate Crystals

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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The added value of synovial fluid centrifugation for monosodium urate and calcium pyrophosphate crystal detection

Clinical Rheumatology ◽

10.1007/s10067-017-3633-6 ◽

2017 ◽

Vol 36 (7) ◽

pp. 1599-1605 ◽

Cited By ~ 4

Author(s):

D. Boumans ◽

M. E. Hettema ◽

H. E. Vonkeman ◽

R. G. Maatman ◽

M. A. van de Laar

Keyword(s):

Synovial Fluid ◽

Calcium Pyrophosphate ◽

Added Value ◽

Monosodium Urate

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P004 Rheumatologist vs pathology department: correlation of crystal identification in synovial fluid analysis

Rheumatology ◽

10.1093/rheumatology/keab247.003 ◽

2021 ◽

Vol 60 (Supplement_1) ◽

Author(s):

A Abdalla

Keyword(s):

Synovial Fluid ◽

University Hospital ◽

Joint Fluid ◽

Correct Identification ◽

Pathology Laboratory ◽

Improvement Project ◽

Fluid Analysis ◽

Polarized Microscopy ◽

To Receive ◽

Msu Crystals

Abstract Background/Aims Crystal arthritis is the commonest inflammatory arthritis in adults. Diagnosis relies mostly on the correct identification of crystals under red-compensated polarized microscopy with assessment of birefringence. This is done routinely in our department when opportunity arises. Failure to appropriately identify crystals may result in lengthy hospitalisations, complications, avoidable repeated urgent visits, and unnecessary cost. We aimed to examine the agreement between rheumatology vs pathology-based microscopy for crystal analysis. There is currently no standardized pathway for synovial fluid crystal analysis in our tertiary centre in Dublin. Methods A prospective study at Mater Misericordiae University Hospital - Dublin, was started in Dec 2019. Synovial fluid samples were obtained from acutely inflamed joints where clinically indicated. Fresh samples which were found to contain crystals (MSU or CPP) by a rheumatology consultant or trained registrar using compensated polarized microscopy, were also simultaneously sent to our pathology laboratory to receive similar analysis. Ethical approval was granted and all patients consented for their joint fluid to receive double analysis. Results 33 samples have been analysed to date. 13 samples of MSU crystals and 20 CPP crystals (table 1). Both rheumatologist and pathologist agreed on all but only one MSU sample. The pathologist identified CPP crystals only on 2/20 samples. The fluid analysis was carried out within the same working day by rheumatologist Vs. median of 2.3 working days for the result by the pathologist. Conclusion The study showed a high agreement between rheumatologists and pathologists on identification of MSU crystals (92%), but very poor agreement on CPP crystals (only 10%). A quality improvement project is currently underway to address this issue and bridge the gap. Majority of Rheumatologists don't routinely perform crystal analysis using polarized microscopy and rely on their local cellular pathology lab for the results. Rheumatologists need to liaise with their local pathologists to optimise and streamline the process of crystal microscopy specially CPP crystals. P004 Table 1:crystals samples analysed through rheumatology and pathologyCPPD positiveMSU positiveRheumatologist2013Pathologist212Total2013 Disclosure A. Abdalla: None.

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