A 3-Day Delay in Synovial Fluid Crystal Identification Did Not Hinder the Reliable Detection of Monosodium Urate and Calcium Pyrophosphate Crystals:

Agreement Among Multiple Observers on Crystal Identification by Synovial Fluid Microscopy

OBJECTIVE

Despite the fact that polarized microscopy remains the gold standard for diagnosing crystal arthritis, some uncertainties hamper full implementation in clinical practice. We undertook this study to analyze the agreement among multiple observers in crystal identification using compensated polarized microscopy, as well as to assess potential outcome modifiers.

METHODS

This was a cross-sectional, observational study with consecutive synovial fluid sampling. Samples were immediately analyzed when possible or kept refrigerated at 4°C. Five observers analyzed them separately, blinded to clinical data, using a compensated polarized optical microscope (400×), through 3 stages (ordinary, simple polarized, and compensated polarized light) to detect and identify crystals. They recorded the presence and type of crystal (no crystals, monosodium urate [MSU], and calcium pyrophosphate dihydrate [CPP]). Interrater agreement was measured by Cohen's kappa. Subanalyses were performed on visualization delay and cumulative expertise. Discrepancies between each stage of the microscopy and the final decision were also examined.

RESULTS

A total of 250 observations from 50 samples completed full assessment. Overall, κ = 0.74 (95% confidence interval [95% CI] 0.64-0.84), indicating good agreement. Agreement for crystal detection was κ = 0.71 (95% CI 0.59-0.82), for MSU was κ = 0.88 (95% CI 0.75-1.0), and for CPP was κ = 0.69 (95% CI 0.56-0.82). Most of the crystal identifications were already made by ordinary light. No differences between observations made before or after 24 hours (P = 0.859) or in expertise on crystal analysis (P = 0.989) were found. Observations performed under ordinary light matched the final diagnosis in 96.8% of cases (242 of 250).

CONCLUSION

Compensated polarized microscopy remained consistent in detecting and identifying crystals in synovial fluid, even when examined among multiple observers, confirming its high utility for clinical practice.

[Gout]

Gout is the most common inflammatory arthritis in men with a rising incidence worldwide. It is a metabolic disease caused by hyperuricemia. Common causes of hyperuricemia, in addition to hereditary reduced renal excretion of urate, include purine over-nutrition, aging, comorbidities and associated medications, some of which increase serum urate levels. The first gout flare represents the signal for deposited urate crystals. If hyperuricemia remains untreated, crystal deposition proceeds and can cause recurrent gout flares, joint destruction and tophi. There is evidence that silent inflammation is ongoing even during asymptomatic stages. Gout patients often exhibit other metabolic, renal and cardiovascular co-morbidities and have higher (cardiovascular) mortality. Therefore, guidelines call for consequent urate lowering strategies to bring serum urate levels to a target at least below 360 µmol/l. The following article summarizes the recent state of knowledge regarding the diagnosis and therapy of gout.

Accuracy of synovial fluid analysis compared to histology for the identification of calcium pyrophosphate crystals: an ancillary study of the OMERACT US Working Group - CPPD subgroup

The aim of this study was to evaluate the accuracy of synovial fluid analysis in the identification of calcium pyrophosphate dihydrate crystals compared to microscopic analysis of joint tissues as the reference standard. This is an ancillary study of an international, multicentre cross-sectional study performed by the calcium pyrophosphate deposition disease (CPPD) subgroup of the OMERACT Ultrasound working group. Consecutive patients with knee osteoarthritis (OA) waiting for total knee replacement surgery were enrolled in the study from 2 participating centres in Mexico and Romania. During the surgical procedures, synovial fluid, menisci and hyaline cartilage were collected and analysed within 48 hours from surgery under transmitted light microscopy and compensated polarised light microscopy for the presence/absence of calcium pyrophosphate crystals. All slides were analysed by expert examiners on site, blinded to other findings. A dichotomic score (absence/ presence) was used for scoring both synovial fluid and tissues. Microscopic analysis of knee tissues was considered the gold standard. Sensitivity, specificity, accuracy, positive and negative predictive values of synovial fluid analysis in the identification of calcium pyrophosphate crystals were calculated. 15 patients (53% female, mean age 68 yo ± 8.4) with OA of grade 3 or 4 according to Kellgren-Lawrence scoring were enrolled. 12 patients (80%) were positive for calcium pyrophosphate crystals at the synovial fluid analysis and 14 (93%) at the tissue microscopic analysis. The overall diagnostic accuracy of synovial fluid analysis compared with histology for CPPD was 87%, with a sensitivity of 86% and a specificity of 100%, the positive predictive value was 100% and the negative predictive value was 33%. In conclusion synovial fluid analysis proved to be an accurate test for the identification of calcium pyrophosphate dihydrate crystals in patients with advanced OA.

[Gout]

Gout is the most common inflammatory arthritis in men with a rising incidence worldwide. It is a metabolic disease caused by hyperuricemia. Common causes of hyperuricemia, in addition to hereditary reduced renal excretion of urate, include purine over-nutrition, aging, comorbidities and associated medications, some of which increase serum urate levels. The first gout flare represents the signal for deposited urate crystals. If hyperuricemia remains untreated, crystal deposition proceeds and can cause recurrent gout flares, joint destruction and tophi. There is evidence that silent inflammation is ongoing even during asymptomatic stages. Gout patients often exhibit other metabolic, renal and cardiovascular co-morbidities and have higher (cardiovascular) mortality. Therefore, guidelines call for consequent urate lowering strategies to bring serum urate levels to a target at least below 360 µmol/l. The following article summarizes the recent state of knowledge regarding the diagnosis and therapy of gout.

Frauen und Gicht – eine diagnostische Herausforderung

Hintergrund Von Gicht sind überwiegend Männer betroffen (m:w; 9:1). Zur Diagnosestellung werden daher in der Regel die klinischen Merkmale einer akuten Monarthritis der unteren Extremität beim Mann herangezogen. Im Moment ist die Datenlage zur Gicht bei Frauen begrenzt. Bei ihnen wird die Gicht oft nicht in die Differenzialdiagnosen einer Arthritis einbezogen. Wir untersuchten daher die Epidemiologie und klinische Präsentation der Gicht bei Frauen und verglichen sie mit denen der Gicht bei Männern. In der Folge wurden die Daten auf Merkmale analysiert, welche bei Frauen die Gicht von Arthritiden anderer Genese unterscheiden und damit Fehldiagnosen vermeiden helfen können.

Methoden Retrospektiv wurden alle Patienten eingeschlossen, die zwischen 2012 und 2018 mit einer primären Entlassungsdiagnose einer Gicht (ICD-10 M10.XX) am Universitätsklinikum Dresden behandelt wurden. Es wurden klinische, laborchemische sowie radiologische Befunde erfasst und deskriptiv sowie multivariat mittels SPSS und R analysiert. In einem zweiten Schritt wurden die Daten von Frauen mit Gichtarthritis mit denen ohne Gicht (Monarthritis anderer Genese) verglichen und mittels univariater sowie multivariater Regressionsanalyse auf Signifikanz geprüft.

Resultate Insgesamt wurden 238 Gicht-Patienten (71 Frauen, 167 Männer) eingeschlossen. Frauen dieser Kohorte waren bei Diagnosestellung im Mittel 20 Jahre älter als Männer und hatten dann insgesamt häufiger mehrere Komorbiditäten: 92% aller Gichtpatientinnen litten an einer Hypertonie (Männer 74%), 84% hatten eine eGFR<60 ml/min (Männer 52%) und 40% hatten kardiovaskuläre Vorereignisse (Männer 14%). 90% nahmen regelmäßig Diuretika ein (Männer 47%). Fast die Hälfte der Frauen hatte bereits eine manifeste Polyarthrose (47 vs. 30% der Männer). Klinisch trat bei Frauen seltener die klassische MTP I-Arthritis (69 vs. 84%) auf. Der Vergleich von Frauen mit durch mikroskopischen Kristallnachweis gesicherter Gicht und Frauen mit Kristall-negativer Monarthritis zeigte signifikante Unterschiede: Frauen mit Gicht waren älter und wiesen signifikant häufiger eine Hypertonie oder kardiovaskuläre Erkrankung, einen Diabetes mellitus Typ 2, einen adipösen Habitus auf oder nahmen Diuretika ein. Bestanden zudem eine eingeschränkte Nierenfunktion sowie eine Hyperurikämie, lag mit hoher Sicherheit eine Gicht vor.

Schlussfolgerungen Die Gicht muss bei einer akuten Monarthritis auch bei Frauen in die Differenzialdiagnose einbezogen werden. Das gilt besonders ab dem Rentenalter und wenn Hypertonie, kardiovaskuläre Erkrankungen, Diabetes mellitus Typ 2 oder Adipositas vorliegen und Diuretika Teil der Dauermedikation sind. Die Einschränkung der Nierenfunktion und eine Serumharnsäure von>390 µmol/l (>6,5 mg/dL) machen eine Gicht sehr wahrscheinlich.

Clinical implications of synovial fluid specimen handling for crystal associated arthritides: A systematic review

AIM

To identify the appropriate methods of synovial fluid (SF) specimen storage, manipulation and handling for crystal associated arthritides (CAA) diagnosis.

METHOD

A systematic literature review was conducted using 5 medical databases to identify diagnostic studies assessing SF specimen handling for calcium pyrophosphate (CPP) and monosodium urate (MSU) crystals identification. All included studies were rated for quality using the Quality Assessment of Diagnostic Accuracy Studies 2.

RESULTS

Fifteen studies, including 2 non-English language manuscripts, were included. Eight studies examined both types of crystals, while 3 studies examined CPP and 4 studies examined MSU crystals only. Overall, MSU crystals were more stable over time compared to CPP crystals. MSU stability was generally independent of time, preservative and temperature. CPP crystals deteriorated with time and were more stable if refrigerated. Ethylenediaminetetraacetic acid (EDTA) was a suitable preservative. Re-examining an initially negative SF sample at 24 hours facilitated detection of additional cases. Very few studies had an overall low risk of bias and applicability.

CONCLUSION

Monosodium urate crystals remain stable over time independent of storage time, temperature and preservative. CPP crystals are mostly stable for 24-48 hours but can deteriorate with time. Overall, SF crystal examination should ideally be done within 24-48 hours. They may be stored at room temperature without any preservative. Otherwise, refrigeration (4°C/39°F) and EDTA preservation is reasonable. Stored SF re-examination, at 24 hours, helps identify a small number of additional MSU and CPP cases. Centrifugation techniques allow better and easier crystal identification, particularly CPP. Most studies were of unclear or low quality.

Persistence of Crystals in Stored Synovial Fluid Samples

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.

[Synovial fluid cytodiagnosis]

Synovial fluid samples represent only a very small percentage of routine work in a cytology laboratory. However, its microscopic examination allows us to observe different types of cells, particles and structures that, due to their morphological characteristics, may provide relevant data for cytodiagnosis. We present certain aspects related to arthrocentesis, the relationship between the gross appearance of synovial fluid and certain pathological processes, as well as the different techniques for processing and staining the smears. Furthermore, we describe the main cytological findings in various pathological conditions of the synovial joints, such as infections (bacterial and fungal), non-infectious inflammatory type (osteoarthrosis, rheumatoid arthritis, connective tissue diseases) and tumoral, distinguishing between primary and metastatic, both solid and haematological neoplasms.

Diagnostic advances in synovial fluid analysis and radiographic identification for crystalline arthritis

PURPOSE OF REVIEW

The present review addresses diagnostic methods for crystalline arthritis including synovial fluid analysis, ultrasound, and dual energy CT scan (DECT).

RECENT FINDINGS

There are new technologies on the horizon to improve the ease, sensitivity, and specificity of synovial fluid analysis. Raman spectroscopy uses the spectral signature that results from a material's unique energy absorption and scatter for crystal identification. Lens-free microscopy directly images synovial fluid aspirate on to a complementary metal-oxide semiconductor chip, providing a high-resolution, wide field of view (∼20 mm) image. Raman spectroscopy and lens-free microscopy may provide additional benefit over compensated polarized light microscopy synovial fluid analysis by quantifying crystal density in synovial fluid samples. Ultrasound and DECT have good sensitivity and specificity for the identification of monosodium urate (MSU) and calcium pyrophosphate (CPP) crystals. However, both have limitations in patients with recent onset gout and low urate burdens.

SUMMARY

New technologies promise improved methods for detection of MSU and CPP crystals. At this time, limitations of these technologies do not replace the need for synovial fluid aspiration for confirmation of crystal detection. None of these technologies address the often concomitant indication to rule out infectious arthritis.

Detection of Calcium Crystals in Knee Osteoarthritis Synovial Fluid: A Comparison Between Polarized Light and Scanning Electron Microscopy

BACKGROUND

The identification of calcium crystals in synovial fluid (SF) of patients with osteoarthritis (OA) represents an important step in understanding the role of these crystals in synovial inflammation and disease progression.

OBJECTIVES

This study aimed to investigate the presence of calcium pyrophosphate (CPP) and basic calcium phosphate (BCP) crystals in SF collected from patients with symptomatic knee OA by scanning electron microscopy (SEM) coupled to x-ray energy dispersive spectroscopy, compensated polarized light microscopy (CPLM), and alizarin red staining.

METHODS

Seventy-four patients with knee OA were included in the study. Synovial fluid samples were collected after arthrocentesis and examined under CPLM for the assessment of CPP crystals. Basic calcium phosphate crystals were evaluated by alizarin red staining. All the samples were examined by SEM. The concordance between the 2 techniques was evaluated by Cohen κ agreement coefficient.

RESULTS

Calcium pyrophosphate and BCP crystals were found, respectively, in 23 (31.1%) and 13 (17.5%) of 74 OA SFs by SEM analysis. Calcium pyrophosphate crystals were identified in 23 (31.1%) of 74 samples by CPLM, whereas BCP crystals were suspected in 27 (36.4%) of 74 samples. According to κ coefficient, the concordance between CPLM and SEM was 0.83 for CPP, and that between alizarin red and SEM was 0.68 for BCP.

CONCLUSIONS

The results of our study showed a high level of concordance between the 2 microscope techniques as regards CPP crystal identification and a lower agreement for BCP crystals. Although this finding highlights the difficulty in identifying BCP crystals by alizarin red staining, the use of SEM remains unsuitable to apply in the clinical setting. Because of the in vitro inflammatory effect of BCP crystals, further work on their analysis in SF could provide important information about the OA process.

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

The aim of the study was to assess the added value of synovial fluid (SF) centrifugation for microscopic monosodium urate (MSU) and calcium pyrophosphate (CPP) crystal detection in patients with arthritis. This is a prospective observational study using SF samples from joints of patients undergoing joint arthrocentesis. Two blinded observers assessed the SF smears by polarized light microscopy for the presence of crystals before as well as after centrifugation. SF samples were collected from 98 patients with arthritis. After exclusion, 87 samples were eligible for inclusion. Of each sample, 2 smears before and after centrifugation were prepared and microscopically examined, resulting in 348 smears per observer. Observer 1 identified MSU crystals in 18.4% and CPP in 9.2% of the smears before as well as after centrifugation. No extra MSU crystal-positive smears were identified after centrifugation. However, centrifugation yielded 4 additional CPP crystal-positive smears. Observer 2 identified MSU crystals in 15.5% and CPP crystals in 6.3% of the smears before as well as after centrifugation. Centrifugation yielded 2 additional MSU crystal-positive smears and 4 CPP crystal-positive smears. Monosodium urate crystals were well recognized without centrifugation. Centrifugation of SF had limited additional value for increasing the amount of MSU-positive smears. However, CPP crystals were identified in a higher number of smears after centrifugation than before. Therefore, centrifugation may be of additional value in selected patients with suspected calcium pyrophosphate deposition disease and to a lesser extent for gout.

Systematic review and quality analysis of emerging diagnostic measures for calcium pyrophosphate crystal deposition disease

OBJECTIVES

Calcium pyrophosphate crystal deposition disease (CPPD) is common, yet prevalence and overall clinical impact remain unclear. Sensitivity and specificity of CPPD reference standards (conventional crystal analysis (CCA) and radiography (CR)) were meta-analysed by EULAR (published 2011). Since then, new diagnostic modalities are emerging. Hence, we updated 2009-2016 literature findings by systematic review and evidence grading, and assessed unmet needs.

METHODS

We performed systematic search of full papers (PubMed, Scopus/EMBASE, Cochrane 2009-2016 databases). Search terms included CPPD, chondrocalcinosis, pseudogout, ultrasound, MRI, dual energy CT (DECT). Paper selection, data abstraction, EULAR evidence level, and Quality Assessment of Diagnostic Accuracy Studies (QUADAS)-2 bias and applicability grading were performed independently by 3 authors.

RESULTS

We included 26 of 111 eligible papers, which showed emergence in CPPD diagnosis of ultrasound (U/S), and to lesser degree, DECT and Raman spectroscopy. U/S detected CPPD crystals in peripheral joints with sensitivity >80%, superior to CR. However, most study designs, though analytical, yielded low EULAR evidence level. DECT was marginally explored for CPPD, compared with 35 published DECT studies in gout. QUADAS-2 grading indicated strong applicability of U/S, DECT and Raman spectroscopy, but high study bias risk (in ∼30% of papers) due to non-controlled designs, and non-randomised subject selection.

CONCLUSIONS

Though CCA and CR remain reference standards for CPPD diagnosis, U/S, DECT and Raman spectroscopy are emerging U/S sensitivity appears to be superior to CR. We identified major unmet needs, including for randomised, blinded, controlled studies of CPPD diagnostic performance and rigorous analyses of 4 T MRI and other emerging modalities.

Evaluation of neutrophil-to-lymphocyte ratio as a marker of inflammatory response in septic arthritis

Is neutrophil-to-lymphocyte ratio high in patients with septic arthritis? Septic arthritis may lead to higher rates of morbidity or even mortality if not diagnosed on time. This study was planned to answer the question that “Could neutrophil-to-lymphocyte ratio be utilized to help to diagnose septic arthritis?” The cohort of the study consisted of 39 patients diagnosed with septic arthritis. After ruling out the patients who did not meet the research’s inclusion criteria, the data of 26 patients were evaluated. The control group was collected from healthy volunteers who were admitted to the internal medicine outpatient clinic for a routine medical checkup at the same period (n = 26). Complete blood count (CBC) parameters, C-reactive protein, erythrocyte sedimentation rate, and neutrophil-to-lymphocyte ratios of the septic arthritis and control groups were compared statistically. In comparison, neutrophil-to-lymphocyte ratios of the septic arthritis group were significantly higher than the control group. In conclusion, neutrophil-to-lymphocyte ratio can be utilized in the emergency department or in outpatient clinics to support the diagnosis of septic arthritis.