Synovial fluid analysis in the diagnosis of joint disease

Dynamics of local gene regulations in synovial fluid leukocytes from horses with lipopolysaccharide-induced arthritis

The role of resident cells such a synoviocytes and chondrocytes in intra-articular inflammation is well-characterized, however the in vivo gene expression patterns of cells (predominantly leukocytes) in the synovial fluid (SF) of an inflamed joint have never previously been investigated. The aim of this study was to investigate gene expression in SF leukocytes from the inflamed joint cavity after intra-articular lipopolysaccharide (LPS) injection in horses to improve our understanding of the temporal regulation of the intra-articular inflammatory response. Gene expression was investigated in SF samples available from six horses 2, 4, 8 16 and 24 h after experimental induction of inflammation in the radiocarpal joint by lipopolysaccharide (LPS) injection. Leukocytic expression of 43 inflammation-related genes was studied using microfluidic high throughput qPCR (Fluidigm®). Expression of 26 genes changed significantly over the 24 h study period, including pro- and anti-inflammatory genes such as interleukin (IL)1, IL6, tumor necrosis factor (TNF), cyclooxygenase 2 (COX2), IL1 receptor antagonist (IL1RN), IL10, and superoxide dismutase 2 (SOD2), chemokine genes, apoptosis-related genes, and genes related to cartilage turnover (matrix metalloproteinase 8 and tissue inhibitor of metalloproteinase 1). The inflammatory responses appeared to be regulated, as an early increase (at 2 h) in expression of the pro-inflammatory genes IL1, IL6, TNF and COX2 was rapidly followed by increased expression (at 4 h) of several anti-inflammatory genes (IL10, IL1RN and SOD2). Similarly, both pro- and anti-apoptotic gene expression as well as expression of chondrodegenerative and chondroprotective genes were activated in SF leukocytes. Thus, the inflammatory response in leukocytes infiltrating the joint in the acute stage of arthritis was well orchestrated in this single-hit LPS-induced arthritis model. This study is the first to describe gene expression patterns in SF-derived leukocytes in vivo during severe joint inflammation, and the results thus expand our knowledge of basic inflammatory mechanisms in the early local response in an inflamed joint.

Concentration of dipotassium ethylenediaminetetraacetic acid but not lithium heparin affects total protein determination in equine synovial fluid

BACKGROUND

Refractometric determination of total protein (TP) in synovial fluid (SF) is commonly used for diagnosis and monitoring of synovial sepsis in horses. Previous studies have shown that elevated concentrations of certain anticoagulants may overestimate refractometric determination of TP concentration.

OBJECTIVES

The aim of the study was to evaluate the effect of different concentrations of dipotassium EDTA (K₂EDTA) and lithium heparin (LH) on TP determination by using a hand-held refractometer in equine synovial fluid.

STUDY DESIGN

Cross-section observational study.

METHODS

Thirty samples of synovial fluid obtained from 22 horses with different synovial conditions were collected. Synovial fluid samples were separated into different aliquots and placed in commercially available collection tubes containing K₂EDTA or LH at four different concentrations (1.76, 3.52, 7.04 and 17.6 mg/ml for K₂EDTA; 16, 32, 64 and 160 IU/ml for LH) . Refractometric TP determination was performed on untreated and K₂EDTA and LH aliquots with a hand-held refractometer and by spectophotometric Biuret method as the gold standard.

RESULTS

Refractometric TP determination was overestimated in SF samples containing 10 times the recommended K₂EDTA concentrations. Lower concentrations of K₂EDTA and LH concentrations did not affect refractometric TP determinations.

MAIN LIMITATIONS

Limited number of samples mostly obtained from large synovial structures.

CONCLUSION

To avoid incorrect TP determination, the use of LH containing collection tubes may be an appropriate alternative when the SF volume available is not enough to fill the K₂EDTA collection tube.

Computational Simulation of Synovial Fluid Kinematics of the Scapholunate Joint

Background: The interaction between wrist kinematics and synovial fluid pressure has yet to be studied. To our knowledge, this is the first study to determine the effect of scapholunate joint kinematics on synovial fluid pressure change using finite volume method. Methods: The carpal bones of a cadaveric hand were obtained from Computed Tomography (CT) scans. CT images of the carpal bones were segmented and reconstructed into 3D model. The 3D synovial fluid model between the scaphoid and lunate was constructed and then used for computational simulations. The kinematics data of scapholunate joint obtained from radioulnar deviation of the wrist was investigated. Results: It was found that the pressure in synovial fluid varied from -1.68 to 2.64 Pa with maximum pressure located at the scaphoid-fluid interface during the radial deviation. For ulnar deviation, the pressure increased gradually from the scaphoid-fluid interface towards the lunate-fluid interface (-1.37 to 0.37 Pa). Conclusions: This new computational model provides a basis for the study of pathomechanics of ligament injury with the inclusion of synovial fluid.

Microfluidic processing of synovial fluid for cytological analysis

Cytological analysis of synovial fluid is widely used in the clinic to assess joint health and disease. However, in general practice, only the total number of white blood cells (WBCs) are available for cytologic evaluation of the joint. Moreover, sufficient volume of synovial aspirates is critical to run conventional analyses, despite limited volume of aspiration that can normally be obtained from a joint. Therefore, there is a lack of consistent and standardized synovial fluid cytological tests in the clinic. To address these shortcomings, we developed a microfluidic platform (Synovial Chip), for the first time in the literature, to achieve repeatable, cost- and time-efficient, and standardized synovial fluid cytological analysis based on specific cell surface markers. Microfluidic channels functionalized with antibodies against specific cell surface antigens are connected in series to capture WBC subpopulations, including CD4+, CD8+, and CD66b+ cells, simultaneously from miniscule volumes (100 μL) of synovial fluid aspirates. Cell capture specificity was evaluated by fluorescent labeling of isolated cells in microchannels and was around 90% for all three WBC subpopulations. Furthermore, we investigated the effect of synovial fluid viscosity on capture efficiency in the microfluidic channels and utilized hyaluronidase enzyme treatment to reduce viscosity and to improve cell capture efficiency (>60%) from synovial fluid samples. Synovial Chip allows efficient and standardized point-of-care isolation and analysis of WBC subpopulations in miniscule volumes of patient synovial fluid samples in the clinic.

Brief Report: Synovial Fluid White Blood Cell Count in Knee Osteoarthritis: Association With Structural Findings and Treatment Response

OBJECTIVE

Osteoarthritis (OA) is a disease with a significant inflammatory component. The aim of this analysis was to determine the relationship between synovial fluid (SF) white blood cell (WBC) count and 2 parameters: disease severity and the reduction in knee pain after intraarticular (IA) steroid injection.

METHODS

Subjects with painful knee OA were recruited for participation in an open-label study of IA steroid therapy. Information was obtained about knee pain using the Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire, and a proportion of subjects underwent magnetic resonance imaging (MRI). Prior to injection with 80 mg methylprednisolone acetate, the index knee joint was aspirated and the fluid obtained was forwarded for assessment of SF WBC count.

RESULTS

Information on SF WBC count was available for 55 subjects. An increase in WBC count category (≤100, 101-250, and 251-1,000 cells/mm3 ) was associated with an increase in synovial tissue volume (P = 0.028) and with other MRI-based measures of disease severity. Also, with each increase in SF WBC count category, there was a greater reduction in KOOS score after steroid injection (for WBC count of ≤100 cells/mm3 [referent], mean ± SD 12.5 ± 15.2; for WBC count of 101-250 cells/mm3 , mean ± SD 21.3 ± 20.6 [β coefficient 0.279, P = 0.049]; for WBC count of 251-1,000 cells/mm3 , mean ± SD 29.3 ± 15.2 [β coefficient 0.320, P = 0.024]).

CONCLUSION

Although all participants in the analysis had SF WBC counts within the "normal" range, total SF WBC count appears to be a biomarker for synovitis on MRI and may also predict response to antiinflammatory treatment.

Evaluation of Hyaluronic Acid Dilutions at Different Concentrations Using a Quartz Crystal Resonator (QCR) for the Potential Diagnosis of Arthritic Diseases

The main objective of this article is to demonstrate through experimental means the capacity of the quartz crystal resonator (QCR) to characterize biological samples of aqueous dilutions of hyaluronic acid according to their viscosity and how this capacity may be useful in the potential diagnosis of arthritic diseases. The synovial fluid is viscous due to the presence of hyaluronic acid, synthesized by synovial lining cells (type B), and secreted into the synovial fluid thus making the fluid viscous. In consequence, aqueous dilutions of hyaluronic acid may be used as samples to emulate the synovial fluid. Due to the viscoelastic and pseudo-plastic behavior of hyaluronic acid, it is necessary to use the Rouse model in order to obtain viscosity values comparable with viscometer measures. A Fungilab viscometer (rheometer) was used to obtain reference measures of the viscosity in each sample in order to compare them with the QCR prototype measures.

Low-dose Spironolactone: Treatment for Osteoarthritis-related Knee Effusion. A Prospective Clinical and Sonographic-based Study

OBJECTIVE

To evaluate the effectiveness of spironolactone as a treatment for osteoarthritis (OA)-related knee effusion in comparison to ibuprofen, cold compresses, and placebo.

METHODS

This study was carried out on 200 patients, aged 40 years or older, attending the outpatient clinic of the Rheumatology Department of Sohag University Hospital with unilateral knee effusion related to OA based on clinical examination, musculoskeletal ultrasonography (US), and synovial fluid analysis. In group 1, 50 patients received spironolactone 25 mg daily for 2 weeks; in group 2, 50 patients took ibuprofen 1200 mg daily for 2 weeks; in group 3, 50 patients used cold compresses 2 times daily for 2 weeks; and in group 4, 50 patients received placebo for the same duration. Fluid > 4 mm was considered as effusion. Decrease in fluid to reach below 4-mm thickness was considered complete improvement, and any decrease that did not reach below 4 mm thickness was considered partial improvement.

RESULTS

The mean age of the participants was 51.2 ± 8.1 years. The mean duration of effusion was 16.5 ± 3.6 days. In group 1, 66% had complete improvement, 20% partial improvement, and 14% no response. In group 2, 24% had complete improvement, 12% partial improvement, and 64% no response. In group 3, 28% had complete improvement, 14% partial improvement, and 58% no response. In group 4, only 6% had complete improvement, 10% partial improvement, and 84% no response.

CONCLUSION

Low-dose spironolactone is a safe and effective medical treatment for OA-related knee effusion.

False-negative rate of gram-stain microscopy for diagnosis of septic arthritis: suggestions for improvement

We quantify the false-negative diagnostic rate of septic arthritis using Gram-stain microscopy of synovial fluid and compare this to values reported in the peer-reviewed literature. We propose a method of improving the diagnostic value of Gram-stain microscopy using Lithium Heparin containers that prevent synovial fluid coagulation. Retrospective study of the Manchester Royal Infirmary microbiology database of patients undergoing synovial fluid Gram-stain and culture between December 2003 and March 2012 was undertaken. The initial cohort of 1896 synovial fluid analyses for suspected septic arthritis was reduced to 143 after exclusion criteria were applied. Analysis of our Gram-stain microscopy yielded 111 false-negative results from a cohort size of 143 positive synovial fluid cultures, giving a false-negative rate of 78%. We report a false-negative rate of Gram-stain microscopy for septic arthritis of 78%. Clinicians should therefore avoid the investigation until a statistically significant data set confirms its efficacy. The investigation's value could be improved by using Lithium Heparin containers to collect homogenous synovial fluid samples. Ongoing research aims to establish how much this could reduce the false-negative rate.