Diagnostic value of synovial fluid microscopy: a reassessment and rationalisation

Leukocyte Esterase and Glucose Reagent Test Can Rule in and Rule out Septic Arthritis

BACKGROUND/AIM

Septic arthritis (SA) requires rapid diagnosis and therapy to avoid joint damage. This study evaluated the diagnostic accuracy of leukocyte esterase (LE) and glucose (GLC) strip tests for diagnosing SA.

PATIENTS AND METHODS

Synovial fluids from 455 patients with atraumatic joint effusions were assessed prospectively over a 5-year period with LE and glucose strip tests. Results were compared to modified Newman criteria for diagnosing joint infections. Synovial fluid cultures, crystal, blood and synovial cell analyses were also performed.

RESULTS

Forty-one patients had SA and 252 non-SA. A positive LE reading combined with negative glucose reading could detect SA with 100% specificity, 85% sensitivity, 100% positive predictive value (PPV) and 98% negative predictive value (NPV). Positive synovial LE reading alone detected SA with 82% specificity, 95% sensitivity, 47% PPV, and 99% NPV.

CONCLUSION

Combined LE and glucose strip tests represent a low-cost tool for rapidly diagnosing or ruling out SA.

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.

Detection of calcium phosphate crystals in the joint fluid of patients with osteoarthritis - analytical approaches and challenges

Clinically, osteoarthritis (OA) is characterised by joint pain, stiffness after immobility, limitation of movement and, in many cases, the presence of basic calcium phosphate (BCP) crystals in the joint fluid. The detection of BCP crystals in the synovial fluid of patients with OA is fraught with challenges due to the submicroscopic size of BCP, the complex nature of the matrix in which they are found and the fact that other crystals can co-exist with them in cases of mixed pathology. Routine analysis of joint crystals still relies almost exclusively on the use of optical microscopy, which has limited applicability for BCP crystal identification due to limited resolution and the inherent subjectivity of the technique. The purpose of this Critical Review is to present an overview of some of the main analytical tools employed in the detection of BCP to date and the potential of emerging technologies such as atomic force microscopy (AFM) and Raman microspectroscopy for this purpose.

Five types of inflammatory arthritis following total knee arthroplasty

Joint effusion after total knee arthroplasty (TKA) is considered as a manifestation of certain inflammatory reactions within prosthetic joints. This study investigated causes of joint effusion following TKA and analyzed phenotypic characteristics of synovial fluid leukocytes for each cause. Forty-six TKAs for rheumatoid arthritis (RA) and 49 TKAs for osteoarthritis (OA) displaying joint effusion were investigated. Causes of joint effusion were clinically identified and frequencies of each cause were compared between RA and OA. Synovial fluid cell phenotypes were analyzed using a fluorescence-activated cell sorter. Clinical diagnoses for joint effusion were classified into five different groups: deep infection (DI); increased activity of RA (IRA); particle-induced synovitis (PS); metal sensitivity (MS); and nonspecific synovitis (NS). The most frequent cause of post-TKA effusion was IRA in RA, and NS in OA. Biomaterial-related arthritis such as PS and MS were more frequent with OA than with RA. Analysis of synovial fluid cell phenotypes revealed that the characteristic cells for each diagnosis were CD16(+)CD14(-) neutrophils in IRA and DI, CD14(+) macrophages in PS, and CD3(+)CD45RO(+) T cells in MS. Post-TKA joint effusion is clinically caused by five different types of arthritis. Phenotypic characteristics of synovial fluid leukocytes reflect joint pathology and contribute to diagnosis and exclusion of biomaterial-related arthritis.

Gross synovial fluid analysis in the differential diagnosis of joint effusion

AIMS

To develop an objective and easy to complete standardised questionnaire for documentation of synovial fluid (SF) gross appearance and use it in the assessment of patients presenting to the rheumatology service with a joint effusion.

METHODS

A standardised questionnaire to record the gross appearance of SF was developed. Interobserver error in recorded observations and direct gross analysis of synovial fluid between four observers was calculated in a pilot study. In a prospective study over 8 months, SF gross analysis and cell count were documented in all patients presenting with a joint effusion. Fusch Rosenthal manual counting chamber was used for calculating SF cell counts.

RESULTS

There was good interobserver agreement on direct gross analysis and between questionnaire assessors (mean kappa 0.889). 80 SF samples were collected. Gross analysis was performed in all samples and cell count in 72. Of the specimens thought to be inflammatory on gross analysis, 31% were found to be non-inflammatory based on cell count; however, 12 of these patients had an established inflammatory arthritis. Gross analysis had a sensitivity of 94% and specificity of 58% when used to determine whether SF is inflammatory or non-inflammatory. The positive and negative predictive values were 0.69 and 0.91 respectively.

CONCLUSIONS

SF cell count did not add any information when SF gross analysis suggested a non-inflammatory process. Gross analysis was better than cell count to determine a potentially septic joint fluid. Further work needs to be done on the value of SF cell counts if gross analysis suggests the fluid to be inflammatory.

Synovial fluid leukocyte count and differential for the diagnosis of prosthetic knee infection

PURPOSE

Criteria for the interpretation of synovial fluid are well established for native joint disorders but lacking for the evaluation of prosthetic joint failure. Our aim was to define cutoff values for synovial fluid leukocyte count and neutrophil percentage for differentiating aseptic failure and prosthetic joint infection.

METHODS

We performed a prospective study of 133 patients in whom synovial fluid specimens were collected before total knee arthroplasty revision between January 1998 and December 2003. Patients with underlying inflammatory joint disease were excluded.

RESULTS

Aseptic failure was diagnosed in 99 patients and prosthetic joint infection was diagnosed in 34 patients. The synovial fluid leukocyte count was significantly higher in patients with prosthetic joint infection (median, 18.9 x 10(3)/microL; range, 0.3 to 178 x 10(3)/microL) than in those with aseptic failure (median, 0.3 x 10(3)/microL; range, 0.1 to 16 x 10(3)/microL; P <0.0001); the neutrophil percentage was also significantly higher in patients with prosthetic joint infection (median [range], 92% [55% to 100%] vs. 7% [0% to 79%], P <0.0001). A leukocyte count of >1.7 x 10(3)/microL had a sensitivity of 94% and a specificity of 88% for diagnosing prosthetic joint infection; a differential of >65% neutrophils had a sensitivity of 97% and a specificity of 98%. Staphylococcus aureus was the only pathogen associated with leukocyte counts >100 x 10(3)/microL.

CONCLUSION

A synovial fluid leukocyte differential of >65% neutrophils (or a leukocyte count of >1.7 x 10(3)/microL) is a sensitive and specific test for the diagnosis of prosthetic knee infection in patients without underlying inflammatory joint disease.

The basis of the synovial fluid analysis

Synovial fluid fills the spaces in the joint cavities. Many diseases can affect the joints and frequently only a direct examination of the tissue or synovial fluid will yield the correct diagnosis. The article presents the basis of the synovial fluid analysis and a relevant decision-making scheme. The reliability and applicability of synovial fluid tests are commented upon. The synovial fluid analysis undoubtedly plays an important role in the management of patients with joint diseases. Due to a lack of interlaboratory comparisons, and therefore expert opinions on the interpretation of results, this knowledge and the acquisition of relevant experience should be encouraged to enable evaluation of the clinical applicability of recent discoveries in synovial fluid pathology.

A 10 year retrospective comparison of the diagnostic usefulness of synovial fluid and synovial biopsy examination

BACKGROUND/AIMS

Synovial fluid examination is thought to be the pathological investigation of choice in most joint disorders, with only a few specific conditions necessitating biopsy, although no evidence based studies are available to support this belief. This study sought to investigate the validity of this assumption.

METHODS

One hundred and three cases in which synovial fluid aspiration and synovial biopsy had both been performed at arthroscopy were studied. The amount of diagnostically useful information produced by each investigation was assessed.

RESULTS

In most cases, both investigations provided the same amount of information and were generally equally specific or equally non-specific. Overall, the biopsy provided more information than the fluid in 29% of cases and vice versa in 18%. When only those cases in which both tests were adequate were considered, the biopsy provided more specific information than the fluid in a small number (9%) of cases, but these cases could not be predicted.

CONCLUSION

The diagnostic usefulness of a biopsy approximates and occasionally exceeds that of a fluid. In the arthroscopic situation, the main advantage of performing both tests is that it provides a "failsafe mechanism" for the rare occasions when one of the samples is inadequate.

Differential effects of cell density on 5-lipoxygenase (5-LO), five-lipoxygenase-activating protein (FLAP) and interleukin-1 beta (IL-1 beta) expression in human neutrophils

We have analyzed the effect of cellular density of 5-Lipoxygenase (5-LO), 5-lipoxygenase-activating protein (FLAP) and interleukin-1 beta (IL-1 beta) gene expression in neutrophils from healthy subjects under culture conditions of low and high cell density. By using RT-PCR techniques, we have found that 5-LO mRNA accumulation decreased in cells cultured at high density, while FLAP mRNA is not affected. De novo 5-LO synthesis, as well as steady-state levels, were reduced in cells maintained at high density. In contrast, the high density conditions lead to the induction of IL-1 beta gene at the RNA and protein levels as measured by RT-PCR and by immunoprecipitation. These results suggest that cellular density plays a role in gene modulation when neutrophils are accumulating at an inflammatory site since neutrophils obtained from the synovial fluid of patients with RA exhibit a protein synthesis profile similar to that observed in peripheral blood neutrophils cultured at high density.

Microscopic analysis of synovial fluid--the perfect diagnostic test?

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Diagnosis of osteoarthritis. Guidelines and current pitfalls

Diagnostic and classification guidelines for osteoarthritis based on clinical and radiographic signs for the most frequently involved joints (knee, hip and hand) have been developed by the American College of Rheumatology. Excellent, new 'high tech' biochemical and imaging methods and guidelines for clinical evaluation of the condition and its therapy have recently been developed and validated. Accordingly, we have consistent and reliable methods for assessing the established condition, but they provide little help in making an early and correct diagnosis for the different forms of osteoarthritis. Both the diagnostic process and the differential diagnosis consist of careful history taking and detailed analysis of the complaints (especially pain), with proper physical examination including a search for the source of pain and tenderness. Not all deformities and pain in and around the joints are signs and symptoms of osteoarthritis, even if the patient is of 'osteoarthritis age' and the joint shows 'osteoarthritis signs' on the x-ray. On the other hand, even if the underlying disease is osteoarthritis, the symptoms and signs may be due to disorders secondary to the basic disease (e.g. enthesopathy or tendinopathy) and the patient's complaints can be helped more easily by physiotherapy and local injections. The course of the disease and close follow-up yield diagnostic clues in cases where the cross-sectional diagnostic measures fail to provide them. Analysis of serum, joint fluid and x-ray films can be of diagnostic value, and other imaging methods (ultrasound, radioisotope scanning, computerised tomography, magnetic resonance imaging, arthroscopy) are also useful tools. Differential diagnosis is not only of theoretical value; misdiagnosis of osteoarthritis leads to either omitted or unnecessary treatment, and causes psychological stress to the patient.

Alteration in T cell/macrophage ratio may reveal lymphocyte proliferation specific for the triggering antigen in reactive arthritis

It has previously been shown that synovial fluid (SF) mononuclear cells (MNC) from patients with reactive arthritis (ReA) and some patients with undifferentiated oligoarthritis (UOA) respond specifically to the triggering bacterium (specific responders). However, in some patients there is a response to two or more bacteria (non-specific responders) and in a third group no response is found (non-responders). We assessed whether the proportion of synovial MNC which were macrophage-monocyte (MaMo) differed among the specific responder, non-specific responder and non-responder groups. There was no difference between the specific (33 +/- 9) and the non-specific (32 +/- 26) groups; non-responders had a higher percentage of MaMo (61.3 +/- 31%) although the difference was not significant. We also investigated whether the specificity of the response to antigen in ReA or UOA SF was altered by changing the T-cell/MaMo ratio. In all five specific responders the immune response remained specific whatever the ratio tested. However, four of the five non-specific responders, but none of the non-responders, developed a specific response to one of the tested antigens by increasing the T cell/MaMo ratio. We conclude that in some patients with a non-specific response, alteration of the T cell/MaMo ratio uncovers a specific response which may identify the triggering antigen.