Synovial White Cell Count Research Articles

Synovial Fluid White Blood Cell Count as a Potential Biomarker for the Clinical Severity of Knee Osteoarthritis: A Prospective Study

Knee osteoarthritis is categorized classically as a non-inflammatory arthropathy. However, there has been increasing evidence regarding the supplementary role of inflammation in the pathogenesis and disease progression of knee osteoarthritis. This study aims to identify a potential correlation between synovial fluid White Blood Cell (SF WBC) count and the severity of knee osteoarthritis clinical presentation. 200 knees (200 patients) were assessed through synovial fluid aspiration and cytology analysis for WBC count. All patients have filled out the Knee Injury and Osteoarthritis Outcome Score for clinical correlation. For the 200 knees, there was a statistically significant positive correlation between the severity of osteoarthritis clinical presentation as expressed by the KOOS and the synovial white blood cell count among the studied cases (p-value < 0.001). There was no statistically significant correlation found between the patient’s age, sex, or side and KOOS or synovial fluid white cell count. The clinical severity of knee osteoarthritis is directly correlated with increased synovial fluid white cell count and hence, SF WBCs may play a role in identifying and grading osteoarthritis clinical severity. This may raise the interest in identifying the role of using specific disease-modifying drugs that deal with the WBC function in cases of osteoarthritis along with other modalities.

Diagnosis of septic arthritis in the acute care setting: the value of routine intra-operative sample culture.

Diagnosing septic arthritis can be challenging and frequently involves clinical assessment, laboratory investigations and synovial fluid analysis. We sought to determine the utility of synovial aspiration and intra-operative synovial fluid and tissue culture for the accurate diagnosis of septic arthritis. We carried out a retrospective review of the records of patients referred to a tertiary orthopaedic unit with possible septic arthritis between 2015 and 2019 inclusive, including clinical and laboratory data for this cohort study. Performance characteristics were determined for synovial aspiration, intra-operative synovial fluid and tissue culture in diagnosing expert review-determined true septic arthritis. Concordance between discharge diagnosis, antibiotic prescribing and true septic arthritis was determined. Of 268 patients identified with suspected septic arthritis, 143 underwent both synovial fluid aspiration and intra-operative synovial fluid and tissue biopsy culture. True septic arthritis was not differentiated significantly by laboratory parameters including serum white cell count (WCC), CRP or synovial WCC. Considering only patients with negative pre-operative synovial aspirate cultures, intra-operative samples led to diagnosis of true septic arthritis in 6 of 63 patients [number needed to treat (NNT) 10.5]. For all patients sampled in theatre, positive synovial tissue biopsy was the only evidence of true septic arthritis in six (NNT 23.9). Despite insufficient microbiological evidence, 27 of the 59 patients who did not have septic arthritis received a discharge diagnosis of septic arthritis, 26 of whom were discharged with antibiotics. Intra-operative sample collection, particularly tissue biopsy, increases the likelihood of a true septic arthritis diagnosis. Such measures might help to reduce diagnostic ambiguity in clinical practice and might therefore reduce overtreatment.

223 Joint Aspirations for Suspected Native Septic Arthritis: A Retrospective Audit of the Diagnostic Accuracy of Aspirations and Clinical Factors Associated with a Diagnosis of Septic Arthritis

Abstract Aim This study aimed to determine the diagnostic accuracy of native joint aspirations for adult septic arthritis (SA), and to determine clinical factors associated with a positive diagnosis of SA. Method Retrospective review of adult patients (≥16yrs) undergoing a major joint aspiration at a single centre over a year period (2019) were identified. Patient demographics, clinical and biochemical data, joint aspiration details, post-aspiration diagnosis, management and patient outcomes were recorded. Culture negative SA was defined as Newman's Criteria C or D. Results There were 161 native joint aspirations identified. The rate of positive diagnosis of SA was 13.0%, (n=21), with 16 (9.9%) culture positive SA and five (3.1%) culture negative SA. The presence of organisms on gram stain, high synovial white cell count (WCC), history of fever, intravenous drug use (IVDU) and previous SA diagnosis were associated with a diagnosis of SA (all p<0.05). A history of crystal arthropathy made the diagnosis of SA less likely (p=0.025). C-reactive protein (CRP) was not statistically different in the SA and non-SA groups (Area Under Curve of ROC=0.63, p=0.55). Conclusion Joint aspiration is still the preferred diagnostic test when it comes to accurately diagnosing native joint SA. However, while synovial culture and gram stain are pending, a high index of suspicion for SA can be based on a combination of patient's presenting symptoms (history of fever), previous SA or IVDU, and a high synovial WCC. These factors can aid the decision as to whether an emergency surgical washout of the joint is indicated.

Joint aspiration and serum markers - do they matter in the diagnosis of native shoulder sepsis? A systematic review

BackgroundSeptic arthritis of the native shoulder is traditionally diagnosed with the same strategies as knee or hip septic arthritis. However, septic arthritis of the shoulder is frequently a missed or delayed diagnosis. Reliance on aspiration and serum markers has been called into question recently. The purpose of this study was to conduct a systematic review investigating the value of joint aspiration and serum markers in the diagnosis of native shoulder joint sepsis.MethodsPubMed/MEDLINE, Scopus, and the Cochrane Library were used in the systematic literature search from January 1, 1960, through January 23, 2021. The primary outcome was to report on the synovial white cell count of patients with native shoulder sepsis. Descriptive statistics using percentages, means, and intraclass correlation coefficient (ICC) values were used to summarize the results.ResultsThirty-one studies, including 25 case series, one case-control, and five cohort studies with a total of 7434 native shoulder joints, were included. There was no standardized approach to diagnosing septic arthritis of the shoulder. Only 10 studies (32%) reported on synovial white cell count with the majority yielding aspiration counts greater than 50,000 cells/mm3, although one study was as low as 30,000 cells/mm3.ConclusionsThe diagnosis of native shoulder joint sepsis lacks uniformity. Methods used to evaluate shoulder sepsis are heterogeneous and may lead to delays or misdiagnosis with devastating sequelae. Synovial white cell count is underutilized and may also present with a lower value than expected, which is likely related to the time interval between symptom onset and diagnosis.

The combined measurement of synovial markers in the diagnosis of periprosthetic joint infection.

Currently there is no single test for periprosthetic joint infection (PJI) that demonstrates an acceptable level of sensitivity. The aim of this pilot study was to identify a combination of biomarkers that could exclude periprosthetic infection prior to revision surgery in hip and knee arthroplasty. This would help in equivocal cases of PJI, such as those with low-virulence organisms, chronic low-grade infection or 'aseptic' loosening. Current research has focused on measuring the levels of biomarkers in the patient's synovial fluid, and these can be combined to improve accuracy. We selected synovial white cell count (SF-WCC) and C-reactive protein (SF-CRP), as they demonstrated an acceptable level of sensitivity and specificity which could be measured using existing equipment. One hundred and sixty-one synovial fluid samples from 134 patients were collected and analysed prospectively using calculated cut-off values of 10mg/l for SF-CRP and 3,000×106/l for SF-WCC. Samples were deemed positive for infection when either of the SF-CRP or SF-WCC values were above the cut-off. The combined test demonstrated a sensitivity greater than 98.5% and specificity above 80% in all samples analysed or looked at separately for total hip replacement and total knee replacement infections. All ten aspirates taken from chronically infected joints tested positive. The combination of SF-CRP and SF-WCC measurement has been shown to have high sensitivity of over 99% in detecting both acute and chronic PJI in both hip and knee arthroplasty. This ability of the test to exclude infection with a high degree of certainty will help in preoperative planning of PJIs.

Evaluation of the inflammatory response to two intra-articular hyaluronic acid formulations in normal equine joints.

Intra-articular (IA) hyaluronic acid (HA) is commonly used to treat equine arthritis. Inflammatory response or "joint flare" is a recognized potential side effect. However, the incidence and severity of inflammation following IA HA injection in horses is not well documented. This study compared the effects of two IA HA formulations of different molecular weight (MW) and a saline control on clinical signs and synovial fluid markers of inflammation in normal equine joints. Eight adult horses each had three healthy fetlock joints randomly assigned to treatment with either 1.4 mega Dalton HA, 0.8 mega Dalton HA or saline control once weekly for three weeks. Clinical evaluation and synovial fluid analysis were performed by blinded assessors. Outcomes of interest were lameness score, joint effusion score and synovial fluid white cell count and differential, total protein, viscosity and serum amyloid A. Joints injected with HA developed significant mild-to-moderate inflammatory responses often associated with lameness and joint effusion compared with saline control joints. The higher MW HA formulation elicited a significantly greater inflammatory response than the lower MW HA after the first injection. In HA injected joints, viscosity remained poor for the entire study. Both IA HA formulations in this study induced an inflammatory response in healthy equine joints. This may have implications for the use of HA in equine joints. The findings in this study are limited to the two HA formulations used. Further investigation of different HA formulations and the use of HA in normal and arthritic equine joints iswarranted.

Serum interleukin 6 could be a valuable initial diagnostic tool in prosthetic knee joint infections.

Accurate preoperative diagnosis of prosthetic joint infection (PJI) in the absence of obvious clinical signs or laboratory findings is challenging. Interleukin 6 (IL-6) has been proposed as an infection marker but supportive data are limited. We studied the diagnostic utility of serum IL-6 in infected total knee arthroplasty (TKA). A prospective cohort study was done in 52 patients (59 knees) with a painful TKA. The abnormal limits for serum IL-6, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), synovial fluid white cell counts (WBC) and synovial fluid neutrophils (PMN) were determined from receiver operating characteristic curves. An infection was defined as the presence of sinus tract or positive culture > two separate tissue or fluid samples. We utilized Mann-Whitney test, Spearman's correlation and Fischer's exact test to determine the sensitivity, specificity, positive predictive value, negative predictive value (NPV) and accuracy of serum IL-6. The optimal threshold concentration of serum IL-6 was 9.14pg/ml. Independently, this yielded a sensitivity, specificity and NPV of 81%, 63% and 85%, respectively, and when combined with synovial fluid WBC, values were 100%, 90%, 100%, respectively. The sensitivity and specificity of ESR (70%, 63.6%), CRP (66.7%, 66.7%), synovial WBC (66.7%, 81%) and synovial PMN (82.4%, 73.7%) were also calculated. Serum IL-6 levels strongly correlate with all markers in PJI. Serum IL-6 improves the diagnosis of PJI over existing methods, especially when combined with synovial fluid WBC. Its optimal usage is as an excellent screening test to rule out infected total knee arthroplasty. Diagnostic Level II.

The role of alpha defensin in prosthetic joint infection (PJI) diagnosis: a literature review.

Prosthetic joint infection (PJI) management is not standardized worldwide and the outcome is frequently unsatisfactory.More and more arthroplasties are now being performed. An increasing number of highly virulent and antibiotic-resistant bacteria and an ageing population of patients presenting with many comorbidities make it necessary to focus on this important topic.Diagnosis of PJI remains challenging because the clinical signs and symptoms and elevation of systemic biomarkers (C-reactive protein, erythrocyte sedimentation rate) may be unclear.In the last few years, the clinical research has focused on synovial fluid biomarkers as a possible breakthrough in the complex scenario of PJI diagnosis.Synovial biomarkers have shown encouraging results and they should be used as diagnostic adjuncts to synovial white cell count and culture bacteriology. Synovial leukocyte esterase (LE) and synovial C-reactive protein (CRP) have been evaluated as good screening measures; however, the most promising synovial fluid biomarker in terms of sensitivity and specificity for PJI seems to be alpha defensin (AD).The laboratory-based alpha defensin enzyme-linked immunosorbent assay (ELISA) test demonstrated the highest ever reported accuracy for PJI diagnosis. However, an alpha defensin lateral flow test could have its place in ruling in a suspected PJI intraoperatively because of its high specificity and rapid results.Cite this article: EFORT Open Rev 2019;4:10-13. DOI: 10.1302/2058-5241.4.180029

A meta-analysis of synovial biomarkers in periprosthetic joint infection: Synovasure™ is less effective than the ELISA-based alpha-defensin test.

(1) To determine the overall accuracy of synovial alpha-defensin, synovial C-reactive protein (sCRP), interleukin-6 (sIL-6), and leukocyte esterase (sLE) as diagnostic markers for periprosthetic joint infection (PJI) and (2) to independantly evaluate the accuracy of both the laboratory-based ELISA alpha-defensin test and the Synovasure™alpha-defensin test kit. An EMBASE and MEDLINE (PubMed) database search was performed using a set of professionally set search terms. Two independent reviewers rated eligible articles. Sensitivity and specificity were meta-analysed using a bivariate random-effects model. Accuracy values were extracted from 42 articles. Pooled sensitivity and specificity of the represented biomarkers were: alpha-defensin ELISA 0.97 (95% CI 0.91-0.99) and 0.97 (95% CI 0.94-0.98), respectively; Synovasure™ test kit assay 0.80 (95% CI 0.65-0.89) and 0.89 (95% CI 0.76-0.96), respectively; sLE 0.79 (95% CI 0.67-0.87) and 0.92 (95% CI 0.87-0.92), respectively; sIL-6 0.76 (95% CI 0.65-0.84) and 0.91 (95% CI 0.88-0.94), respectively; sCRP 0.86 (95% CI 0.81-0.91) and 0.90 (95% CI 0.86-0.93), respectively. The labararory-based alpha-defensin ELISA test showed the highest ever reported accuracy for PJI diagnosis. However, this did not apply for the Synovasure™ alpha-defensin test, which was comparable in its overall diagnostic accuracy to sCRP, sIL-6 and sLE. The later biomarkers also did not yield an overall diagnostic accuracy higher than that previously reported for synovial white cell count (sWBC) or culture bacteriology. Based on current evidence, no synovial biomarker should be applied as a standalone diagnostic tool. Furthermore, the use of the laboratory-based alpha-defensin ELISA test should be encouraged, still, the Synovasure™alpha-defensin test kitshould be critically appreciated. III.

Excellent AUC for joint fluid cytology in the detection/exclusion of hip and knee prosthetic joint infection.

The aim of this study was to evaluate the characteristics of synovial fluid (SF) white cell count (SWCC) and neutrophil/lymphocyte percentage in the diagnosis of prosthetic joint infection (PJI) for particular threshold values. This was a prospective study of 391 patients in whom SF specimens were collected before total joint replacement revisions. SF was aspirated before joint capsule incision. The PJI diagnosis was based only on non-SF data. Receiver operating characteristic plots were constructed for the SWCC and differential counts of leukocytes in aspirated fluid. Logistic binomic regression was used to distinguish infected and non-infected cases in the combined data. PJI was diagnosed in 78 patients, and aseptic revision in 313 patients. The areas (AUC) under the curve for the SWCC, the neutrophil and lymphocyte percentages were 0.974, 0.962, and 0.951, respectively. The optimal cut-off for PJI was 3,450 cells/μL, 74.6% neutrophils, and 14.6% lymphocytes. Positive likelihood ratios for the SWCC, neutrophil and lymphocyte percentages were 19.0, 10.4, and 9.5, respectively. Negative likelihood ratios for the SWCC, neutrophil and lymphocyte percentages were 0.06, 0.076, and 0.092, respectively. Based on AUC, the present study identified cut-off values for the SWCC and differential leukocyte count for the diagnosis of PJI. The likelihood ratio for positive/negative SWCCs can significantly change the pre-test probability of PJI.

Synovial fluid white cell count and histopathological examination of periprosthetic tissue samples (frozen and permanent sections) in the diagnosis of prosthetic knee infection

Abstract The aim of the study was to determine prospectively the importance of synovial fluid white cell count and intraoperative frozen and permanent sections analysis (number of polymorphonuclear leukocytes per high-power field) in the diagnosis of septic total knee arthroplasty. There were studied prospectively 72 patients who needed a revision total knee arthroplasty between 2013-2015. 30 patients were diagnosed with prosthetic joint infection due to high rates of ESR (93%) and CRP (90%) and preoperative positive culture from aspirated synovial fluid and 42 patients were considered to have aseptic failure according to negative preoperative culture from joint aspirate. For all the patients was analysed synovial fluid white cell count and histopathological aspect of intraoperative frozen and permanent sections of periprosthetic tissue. The results showed a median value of 13800 of sinovial white cells count for infected knee and 92 for noninfected knee. 90% of the patients with joint infection had more than 5 polymorphonuclear leukocytes per high power field on intraoperative frozen sections and 83% on permanent sections. None of the patients from aseptic group had more than 5 polymorphonuclear leukocytes per field on permanent sections. The erythrocyte sedimentation rate and C-reactive protein level can be supplemented with cultures of aspirated joint fluid and fluid white cell count to confirm the diagnosis of periprosthetic infection. When the preoperative diagnosis remain unclear, the histological examination of frozen or permanent sections of periprosthetic tissue with at least 5 polymorphonuclear leukocytes per high power field, is predictive for the presence of infection.

Diagnosing Septic Arthritis in the Synovial White Cell Count "Gray Zone".

Differentiating septic arthritis of the pediatric hip from other causes of hip pain and effusion continues to present a diagnostic challenge for the clinician. Although septic arthritis traditionally has been reported to have a synovial white blood cell count of 75,000cells/mm3 or greater, lower counts can be seen in this condition. In cases where a synovial sample has been obtained and the cell count falls in the intermediate range between 25,000 and 75,000cells/mm(3), it is unclear what proportion of these cases may be truly septic hips. In this evidence-based review, we examine Heyworth et al's study focusing on the predictive value of this intermediate white cell count range in a Lyme-endemic region.

Synovial White Cell Count in the Diagnosis of Septic Arthritis: Are Current Diagnostic Practices Appropriate?

Introduction & aims: Septic arthritis is an emergency, potentially causing irreversible joint destruction and disability. Synovial WCC and polymorphonuclear cell percentage are the best predictors of septic arthritis likelihood. Yet, synovial white cell and differential count are not routinely assessed. We aim to investigate the incidence of failure to perform these tests, and to develop correct synovial fluid analysis practices. Method: This is a retrospective analysis of native joints having undergone arthrocentesis for suspicion of septic arthritis at Box Hill Hospital (BHH) during September 2011 and September 2013 inclusive. Recruitment was from the Eastern Health Decision Support Service (DSS), a database compiled from all systems within Eastern Health, of which BHH is a member. The study was limited to large joints, including hip, knee and shoulder. All prosthetic joints were excluded from the patient population. All patient histories were examined for suspicion of septic arthritis and subsequent arthrocentesis. Pathology records were accessed to determine incidence of cell count and differential. Results: One hundred and thirty-six cases of joint aspirations were identified within the time frame, of which sixty-seven fitted our criteria for evaluation. All but two cases were delivered using the DSS, which was limited to data compiled only until June 2013. The two remaining cases were identified with a manual search of the radiology and pathology databases from June to September 2013. 22 of the 67 joint aspirates studied did not have a cell count carried out. Four of these 22 cases had a diagnosis of septic arthritis. In five aspirates, there was a failure to confirm a definite diagnosis and they were thus conservatively treated as a septic joint. The remaining acute joints in which no cell count was done were gout (7 cases), pseudogout (5 cases) and rheumatoid arthritis (1 case). Cell counts were not routinely detected for a variety of reasons. Eleven aspirates were deemed too viscous, and in eight cases the sample had clotted prior to pathologist assessment. Two cases had insufficient volume, and one sample was too bloodstained to calculate a cell count and differential; likely due to traumatic aspiration. Conclusions: 33% of acute monoarthritis’ evaluated over the study period failed to have a synovial fluid WCC and differential. This may be due to inadequate samples, or lack of appropriate collection tube. Better education is required for appropriate collection and test requesting wherein a diagnosis of septic arthritis is in question.

Kingella kingae septic arthritis in children: recognising an elusive pathogen

PurposeKingella kingae is an increasingly identified cause of musculoskeletal infections in young children. We report our experience with a recently developed polymerase chain reaction (PCR) method and review the clinical course of children diagnosed with K. kingae septic arthritis in a tertiary referral paediatric hospital.MethodsAll positive cases of K. kingae identified by PCR analysis of synovial fluid from August 2010 until July 2013 were included. A chart review was undertaken to determine history, presentation and management.Results27 Children (14 male, 13 female) had PCR positive synovial fluid samples for K. kingae with median age of 19 months (range 4 months to 5 years 3 months). The sites of infection were knee (17 cases), hip (2 cases), ankle (5 cases), shoulder (2 cases) and elbow. The median temperature on presentation was 37.1 °C, median peripheral white blood cell count 12.4 (9.9–13.8) × 109/L, erythrocyte sedimentation rate 55 (48–60) mm/h and C-reactive protein 24 (8–47) mg/L. The median synovial fluid white cell count was 21.8 (16.7–45.0) × 109/L. Routine cultures identified K. kingae in only two synovial fluid samples. Two samples were additionally positive for Staphylococcus aureus.ConclusionsKingella kingae is a significant cause of septic arthritis in young children. The authors recommend maintaining a high index of suspicion in young children presenting with joint inflammation, especially if indices of infection are mild. It appears likely that children historically treated with antibiotics for “culture negative” septic arthritis were infected with K. kingae. PCR techniques for detection of K. kingae should be encouraged.

Lyme Arthritis: A Comparison of Presentation, Synovial Fluid Analysis, and Treatment Course in Children and Adults

This case series examines differences in the presentation, management, and outcome of Lyme arthritis between the pediatric and adult population. We reviewed charts of pediatric and adult patients evaluated for Lyme arthritis by rheumatologists and pediatric infectious disease specialists in Portland, Maine between January 2002 and July 2008. Patients included for analysis had documented joint swelling and positive Lyme serology. Data on clinical presentation, synovial fluid and peripheral blood results, treatment, and clinical course were analyzed. Twenty-nine adults and 52 children met case criteria for Lyme arthritis. Children were more likely than adults to present acutely (P < 0.0001) and also had higher mean peripheral blood (P = 0.05) and synovial fluid white blood cell counts (P < 0.0001). Lyme arthritis was more frequently suspected in children at presentation (P = 0.04). There was no difference between children and adults with respect to suspicion for septic arthritis, hospitalization, or surgical intervention. Adults received more antibiotic courses (P = 0.007) and were more likely to have intravenous antibiotics in subsequent treatment courses (P = 0.006). Children were more likely to have normal function within 4 weeks of initiating antibiotic treatment (P < 0.0001). Children with Lyme arthritis were more likely to present acutely with higher synovial white cell counts than adults. We did not, however, observe a significant difference in hospitalization or surgical management. Children had more prompt resolution of their joint swelling and received less treatment overall.

Reply to the Letter to the Editor: Another Look: Is There a Flaw to Current Hip Septic Arthritis Diagnostic Algorithms?

Reply to the Letter to the Editor: Another Look: Is There a Flaw to Current Hip Septic Arthritis Diagnostic Algorithms?

The use of CRP within a clinical prediction algorithm for the differentiation of septic arthritis and transient synovitis in children

Clinical prediction algorithms are used to differentiate transient synovitis from septic arthritis. These algorithms typically include the erythrocyte sedimentation rate (ESR), although in clinical practice measurement of the C-reactive protein (CRP) has largely replaced the ESR. We evaluated the use of CRP in a predictive algorithm. The records of 311 children with an effusion of the hip, which was confirmed on ultrasound, were reviewed (mean age 5.3 years (0.2 to 15.1)). Of these, 269 resolved without intervention and without long-term sequelae and were considered to have had transient synovitis. The remaining 42 underwent arthrotomy because of suspicion of septic arthritis. Infection was confirmed in 29 (18 had micro-organisms isolated and 11 had a high synovial fluid white cell count). In the remaining 13 no evidence of infection was found and they were also considered to have had transient synovitis. In total 29 hips were categorised as septic arthritis and 282 as transient synovitis. The temperature, weight-bearing status, peripheral white blood cell count and CRP was reviewed in each patient. A CRP > 20 mg/l was the strongest independent risk factor for septic arthritis (odds ratio 81.9, p < 0.001). A multivariable prediction model revealed that only two determinants (weight-bearing status and CRP > 20 mg/l) were independent in differentiating septic arthritis from transient synovitis. Individuals with neither predictor had a < 1% probability of septic arthritis, but those with both had a 74% probability of septic arthritis. A two-variable algorithm can therefore quantify the risk of septic arthritis, and is an excellent negative predictor.

Septic arthritis: current diagnostic and therapeutic algorithm

To propose and discuss an evidence-based algorithm for the diagnosis and treatment of bacterial septic arthritis. Also, to review the recent literature on emerging management strategies and discuss the potential impact of these developments on clinical practice. Evidence-based guidelines have recently been published to assist in the diagnosis and management of suspected and confirmed septic arthritis. All suspected septic joints should be aspirated and the synovial fluid examined by microscopy for the presence of crystals and microorganisms. There is controversy surrounding the diagnostic utility of quantifying the synovial fluid white cell count, with two recent systematic reviews reaching opposite conclusions. The emergence of multidrug resistant pathogens has led to a search for alternative antimicrobial agents such as linezolid. Studies in animals and children have suggested that corticosteroid therapy may be a useful adjunct to conventional antibiotic therapy. Research using experimental murine models of septic arthritis is also generating novel immunotherapeutic targets as potential adjuncts to antibiotic regimens. There is a striking paucity of high-quality evidence upon which to base guidelines on the management of the hot-swollen joint. Ultimately, the diagnosis of septic arthritis rests on the opinion of a clinician experienced in the assessment of musculoskeletal disease. Future research may provide alternative investigative and treatment strategies to improve the accuracy of diagnosis as well as the outcome in this group of patients.

Another Look at Synovial Fluid Leukocytosis and Infection

Synovial fluid white blood cell counts are considered to be useful in diagnosing infectious arthritis, however, considerable overlap exists between infectious and noninfectious types of inflammatory arthritis. We undertook this review of synovial fluid studies at our institution to better define this degree of overlap and characterize the features of infectious arthritis in relationship to synovial fluid white cell counts. The records of 202 consecutive patients with synovial fluid white blood cell counts >2000/mm were reviewed. Infectious arthritis was diagnosed in 77% (10/13) of patients with counts >100,000, 47% (8/17) in the 50,000-100,000 range, and 5% (9/172) with counts <50,000. Crystal-induced arthritis and rheumatoid arthritis made up 81% of patients in the 15,000-50,000 range. Overall, 10 of 27 (37%) cases of infectious arthritis had white cell counts >100,000, and 18 of 27 (67%) had counts >50,000. A majority of these infections (14/18) were related to Staphylococcus aureus, while 5 of 7 infections associated with counts <20,000 were associated with atypical organisms. This study confirms that a majority of patients with very high synovial fluid white blood cell counts have infectious arthritis, and that the likelihood of infection is markedly reduced, but certainly not excluded, below this level. The presence of atypical infections in a small percentage of patients with low counts emphasizes the importance of clinical judgment in evaluating all patients with inflammatory arthritis, regardless of synovial fluid white cell counts.

Measurement of glycosaminoglycans and keratan sulphate in canine arthropathies

Glycosaminoglycans ( gag) and keratan sulphate ( ks) were measured in sera and synovial fluids from dogs with either osteoarthritis ( oa) or rupture of the cranial cruciate ligament ( ccl) and normal dogs. The dogs with oa had higher synovial fluid gag levels (P<0·002) and serum KS (P<0·03) compared to the normal dogs. No significant differences in serum gag were found in either group. In both oa and rupture of the ccl, gag levels were increased in the synovial fluid from the affected joint compared with the clinically normal (inactive) contralateral joint. Neither gag nor ks measurements correlated with serum and synovial fluid antibodies to collagen type II, synovial fluid white cell count or age of dog. It is unlikely that the measurement of these cartilage breakdown products is of value for diagnostic or prognostic use in canine arthropathies.