Synovial fluid leukocytosis in bacterial arthritis vs. reactive arthritis and rheumatoid arthritis in the adult knee

Native and prosthetic septic arthritis in a university hospital in Saudi Arabia: A retrospective study

BACKGROUND

Septic arthritis, whether native or prosthetic, poses a significant challenge in clinical practice due to its potentially devastating consequences. Despite its clinical importance, there remains a dearth of comprehensive studies and standardized diagnostic criteria, particularly in the Kingdom of Saudi Arabia.

AIM

To investigate the epidemiology, microbiological profiles, and clinical characteristics of native and prosthetic septic joints in the Saudi Arabian population.

METHODS

Medical records of patients diagnosed with septic arthritis between January 1, 2015, and December 31, 2022, were retrospectively reviewed. Data regarding patient demographics, clinical presentation, microbiological cultures, treatment modalities, and outcomes were analyzed.

RESULTS

In a retrospective review of 52 cases of septic arthritis, a balanced gender distribution was observed (1:1 ratio), with the knee being the most commonly affected joint (80.8%). Methicillin-resistant Staphylococcus aureus predominated in native joints (24.2%), while Brucella spp. was more prevalent in prosthetic joints (21.1%). Joint preservation was achieved in most cases (84.6%), with no significant difference in clinical features between native and prosthetic joints. However, certain comorbidities were more common in native joint cases, including renal impairment (P = 0.002), hemodialysis (P = 0.004), heart disease (P = 0.013), and chronic liver disease (P = 0.048). At the same time, osteoarthritis was more prevalent in prosthetic joint cases (P = 0.013). Vancomycin was the most frequently used antibiotic (26.9%), and most patients received antibiotics before joint aspiration (57.7%). Surgical intervention, predominantly arthrotomy, was required in most cases (32.7%). Notably, a significant association was found between joint type and mortality (odds ratio = 0.587, P = 0.048), as well as the Charlson comorbidity index and mortality (P = 0.001).

CONCLUSION

This study highlighted distinctive microbiological profiles and etiological factors in septic arthritis cases in the Saudi Arabian population.

The Effect of Crystal Arthropathy on the Diagnostic Criteria of Native Septic Arthritis

INTRODUCTION

Distinguishing between septic arthritis and crystal arthropathy flares can be challenging. The purpose of this study was to determine how the presence of synovial crystals affects the diagnostic criteria of septic arthritis.

METHODS

A retrospective review identified patients undergoing joint aspirations to rule out native septic arthritis. Differences between septic arthritis presenting with and without synovial crystals were analyzed. A receiver-operating characteristic curve was plotted for laboratory markers to determine the area under the curve, or diagnostic accuracy, for septic arthritis and to evaluate thresholds that maximized sensitivity and specificity.

RESULTS

There were 302 joint aspirations in 267 patients. Septic arthritis was diagnosed in 17.9% (54/302). Patients with synovial crystals were less likely to have septic arthritis (4.2% [5/119] vs. 26.8% [49/183], P < 0.0001). Septic arthritis in patients with no synovial crystals was associated with fever and a higher synovial white blood cell (WBC) count, synovial polymorphonuclear cell percentage (PMN%), serum WBC, and C-reactive protein (CRP) ( P < 0.05). Septic arthritis in patients with synovial crystals was only associated with inability to bear weight and a higher synovial WBC and CRP ( P < 0.05). Synovial PMN% was considered nondiagnostic of septic arthritis (area under the curve 0.56) in patients with crystals while synovial WBC and CRP had acceptable (0.76) and excellent (0.83) diagnostic utility, respectively. The WBC and CRP value thresholds that maximized sensitivity and specificity for septic arthritis were greater in patients with crystals (21,600 vs. 17,954 cells/μL and 125 vs. 69 mg/L, respectively).

DISCUSSION

The presence of synovial crystals reduced the likelihood of septic arthritis and altered the laboratory diagnostic criteria. PMN% was nondiagnostic in the setting of synovial crystals.

Arthroscopic Treatment of the Septic Ankle

Ankle joint sepsis is a relatively rare but potentially devastating pathologic process of the lower extremity that requires expeditious identification and management. Establishing the diagnosis of ankle joint sepsis is often challenging as it may present with concomitant pathologies and often lacks consistency in regard to classic clinical characteristics. Once a diagnosis has been established, prompt management is imperative to minimize the potential for long-term sequelae. The purpose of this chapter is to address the diagnosis and management of the septic ankle with a focus on arthroscopic treatment.

Clinical prediction rule for bacterial arthritis: Chi-squared automatic interaction detector decision tree analysis model

Objectives:

Differences in demographic factors, symptoms, and laboratory data between bacterial and non-bacterial arthritis have not been defined. We aimed to identify predictors of bacterial arthritis, excluding synovial testing.

Methods:

This retrospective cross-sectional survey was performed at a university hospital. All patients included received arthrocentesis from January 1, 2010, to December 31, 2020. Clinical information was gathered from medical charts from the time of synovial fluid sample collection. Factors potentially predictive of bacterial arthritis were analyzed using the Student’s t-test or chi-squared test, and the chi-squared automatic interaction detector decision tree analysis. The resulting subgroups were divided into three groups according to the risk of bacterial arthritis: low-risk, intermediate-risk, or high-risk groups.

Results:

A total of 460 patients (male/female = 229/231; mean ± standard deviation age, 70.26 ± 17.66 years) were included, of whom 68 patients (14.8%) had bacterial arthritis. The chi-squared automatic interaction detector decision tree analysis revealed that patients with C-reactive protein > 21.09 mg/dL (incidence of septic arthritis: 48.7%) and C-reactive protein ⩽ 21.09 mg/dL plus 27.70 < platelet count ⩽ 30.70 × 10⁴/μL (incidence: 36.1%) were high-risk groups.

Conclusions:

Our results emphasize that patients categorized as high risk of bacterial arthritis, and appropriate treatment could be initiated as soon as possible.

What are the best diagnostic tests for diagnosing bacterial arthritis of a native joint? : a systematic review of 27 studies

AIMS

This study aimed to answer two questions: what are the best diagnostic methods for diagnosing bacterial arthritis of a native joint?; and what are the most commonly used definitions for bacterial arthritis of a native joint?

METHODS

We performed a search of PubMed, Embase, and Cochrane libraries for relevant studies published between January 1980 and April 2020. Of 3,209 identified studies, we included 27 after full screening. Sensitivity, specificity, area under the curve, and Youden index of diagnostic tests were extracted from included studies. We grouped test characteristics per diagnostic modality. We extracted the definitions used to establish a definitive diagnosis of bacterial arthritis of a native joint per study.

RESULTS

Overall, 28 unique diagnostic tests for diagnosing bacterial arthritis of a native joint were identified. The following five tests were deemed most useful: serum ESR (sensitivity: 34% to 100%, specificity: 23% to 93%), serum CRP (sensitivity: 58% to 100%, specificity: 0% to 96%), serum procalcitonin (sensitivity: 0% to 100%, specificity: 68% to 100%), the proportion of synovial polymorphonuclear cells (sensitivity: 42% to 100%, specificity: 54% to 94%), and the gram stain of synovial fluid (sensitivity: 27% to 81%, specificity: 99% to 100%).

CONCLUSION

Diagnostic methods with relatively high sensitivities, such as serum CRP, ESR, and synovial polymorphonuclear cells, are useful for screening. Diagnostic methods with a relatively high specificity, such as serum procalcitonin and synovial fluid gram stain, are useful for establishing a diagnosis of bacterial arthritis. This review helps to interpret the value of various diagnostic tests for diagnosing bacterial arthritis of a native joint in clinical practice. Cite this article: Bone Joint J 2021;103-B(12):1745-1753.

Human diamine oxidase is readily released from activated neutrophils ex vivo and in vivo but is rarely elevated in bacteremic patients

During human diamine oxidase (DAO) ELISA development we noticed that in serum DAO concentrations appear to be higher when compared to plasma. Neutrophils contain DAO in the specific granules and we hypothesized that DAO is released from neutrophils during serum coagulation. If activation of neutrophils can release DAO, its concentrations might be elevated in vivo after lipopolysaccharide (LPS) administration and in bacteremic patients. Using blood from healthy volunteers DAO concentrations were measured ex vivo in serum, citrate, EDTA and heparin plasma over several hours and after activation of neutrophils. Lipopolysaccharide and granulocyte-colony stimulating factor (G-CSF) were administered to 15 and 8 healthy volunteers, respectively and DAO concentrations were measured at different timepoints. DAO antigen levels were also determined in three different subcohorts of patients with culture-proven bacteremia and high C-reactive protein (CRP) levels. DAO concentrations were elevated in a time-dependent manner in serum but not in EDTA or citrate plasma (P < 0.01). Neutrophil activation using phorbol myristate acetate (PMA) and zymosan dose-dependently caused DAO concentrations to be elevated more than 10-fold at both 22°C and 37°C (both P-values <0.001). Administration of LPS to healthy volunteers released DAO from neutrophils (P < 0.001). Of the 55 different bacteremic patients selected from three independent cohorts only 3 (5.4%) showed highly elevated DAO concentrations. Serum DAO concentrations do not accurately reflect circulating enzyme levels but coagulation-induced neutrophil activation and consequently DAO release. Only a few bacteremic patients show high DAO concentrations able to degrade histamine rapidly.

Differential characteristics and management of pseudoseptic arthritis following hyaluronic acid injection is a rare complication: a systematic review

IMPORTANCE

Acute pseudoseptic arthritis is a rare complication of hyaluronic acid (HA) injections that is not well documented in the literature. Practitioners initially suspect the symptoms of this complication to represent septic arthritis, cautiously prescribing antibiotics. This review identifies that time to presentation of symptoms postinjection, negative cell cultures and lack of crystallisation could be used as differentials to suspect pseudoseptic arthritis and to prescribe anti-inflammatory drugs while closely monitoring change of symptoms.

OBJECTIVE

The purpose of this study was to describe the presentation, diagnosis and treatment of pseudoseptic arthritis.

EVIDENCE REVIEW

A systematic review of the literature was conducted for studies reporting the use of HA injections for osteoarthritis resulting in pseudoseptic arthritis using the electronic databases MEDLINE, Embase and PubMed. Pertinent data were abstracted from the search yield. A unique case of a pseudoseptic reaction is also presented.

FINDINGS

A total of 11 studies (28 cases), all of level IV and V evidence were included in this review. Reported cases of pseudoseptic arthritis in the literature present with severe joint pain (100%), effusion (100%), inability to weight-bear, functional impairment, and occasionally fever (22.2%). C reactive protein and erythrocyte sedimentation rate are generally elevated (71.4% and 85.7%, respectively), and leucocytosis above 10 000 was less common (50%). All reported cases in the literature identified aseptic growth on arthrocentesis, despite four cases (15.4%) reporting synovial leucocyte counts above 50 000. The presented case is the highest reported leucocyte count at 1 74 960 cells/mm³.

CONCLUSIONS AND RELEVANCE

Acute pseudoseptic arthritis is rare, but a number of cases have been reported in the literature. A high degree of suspicion for pseudoseptic arthritis may be maintained in patients who present under 72 hours following HA injection. Initial antibiotic treatment, along with anti-inflammatory medications until cultures are confirmed to be negative at 5 days, is a cautious approach. However, the strength of this conclusion is limited by the few reported cases. Ultimately, this review is intended to inform practitioners of the symptoms, diagnosis and treatment of this complication, such that it could be safely differentiated from septic arthritis.

LEVEL OF EVIDENCE

IV.

Subarticular Inflammatory Pseudoabscesses: A Pathologic Study With Clinical Correlation

Abnormal accumulation of neutrophils in a subarticular bone usually raises the concern for osteomyelitis or septic arthritis, a disabling and potentially life-threatening medical condition. At the pathology department of a specialized orthopedic institute, we observed a distinct pattern of subarticular inflammation mimicking infection characterized by collections of neutrophils, macrophages, and fibrin in pseudocystic spaces of variable size and extent in the superficial subarticular bone not accompanied by granulation tissue or necrosis. We coined the term "inflammatory pseudoabscess" to describe these accumulations. From 1997-2015, we reported inflammatory pseudoabscesses in 157 primary arthroplasty/osteotomy specimens from 143 patients without penetrating trauma or hardware in the affected joint. The predominant gross and histologic features were those of destructive/inflammatory joint disease, including lymphoplasmacytic synovitis (95.3%), subchondral osseous chronic inflammation (80.3%), exudative synovitis (58.0%), synovial pannus (52.0%), and marginal erosions of articular cartilage and/or subarticular bone (43.3%). Clinical information was available in 137 (95.8%) patients, 107 (overall: 74.8%) of whom had preoperatively or postoperatively diagnosed inflammatory arthropathy, most commonly rheumatoid arthritis. The remaining 30 (overall: 21.0%) patients had no documented inflammatory disorders, but some had bilateral or multijoint arthropathy, hands/feet involvement, lymphoplasmacytic synovitis, ulcerative colitis, or family history of inflammatory arthropathy. There was no documented infection-associated implant failure. We believe that inflammatory pseudoabscess represents an intraosseous manifestation of noninfectious inflammatory disorders of joints. This feature should be recognized by pathologists and used to suggest further clinical evaluation for undiagnosed inflammatory joint diseases.

Centrifugation may eliminate false-positive leucocyte esterase strip test results caused by inflammatory arthritis in the diagnosis of knee infection: A pilot study

Aims

The purpose of this study was to validate our hypothesis that centrifugation may eliminate false-positive leucocyte esterase (LE) strip test results caused by autoimmune diseases in the diagnosis of knee infection.

Methods

Between January 2016 and May 2019, 83 cases, including 33 cases of septic arthritis and 50 cases of aseptic arthritis, were enrolled in this study. To further validate our hypothesis, another 34 cases of inflammatory arthritis from the Department of Rheumatology of our institution were also included. After aspiration, one drop of synovial fluid was applied to LE strips before and after centrifugation. The results were recorded after approximately three minutes according to the different colour grades on the colour chart. The differences of LE results between each cohort were analyzed.

Results

Before centrifugation, 46% (23/50) of the LE strip tests in the aseptic arthritis group were false-positives. Most of the false-positive results were due to inflammatory arthritis; after centrifugation, 78.3% (18/23) of the tests yielded negative results. Similar results were observed in cases from the Department of Rheumatology. The sensitivity of the centrifuged LE strip test was 0.818 (0.639 to 0.924), which is still an acceptable level compared with the uncentrifuged results, which yielded a sensitivity of 0.909 (0.745 to 0.976). However, the specificity was increased from 0.540 (0.395 to 0.679) to 0.900 (0.774 to 0.963) after centrifugation.

Conclusion

Although inflammatory arthritis can yield a false-positive LE strip test result in the diagnosis of knee infection, centrifugation may eliminate these false-positive results.

Cite this article: Bone Joint Res. 2020;9(5):236–241.

The etiology of rheumatoid arthritis

Rheumatoid arthritis is a heterogeneous disease, which can be, based on data combining genetic risk factors and autoantibodies, sub-classified into ACPA-positive and -negative RA. Presence of ACPA and RF as well as rising CRP-levels in some patients years before onset of clinical symptoms indicate that relevant immune responses for RA development are initiated very early. ACPA are highly specific for RA, whereas RF can also be found among healthy (elderly) individuals and patients with other autoimmune diseases or infection. The most important genetic risk factor for RA development, the shared epitope alleles, resides in the MHC class II region. Shared epitope alleles, however, only predispose to the development of ACPA-positive RA. Smoking is thus far the most important environmental risk factor associated with the development of RA. Studies on synovitis have shown the importance not only of adaptive but also of innate immune responses. In summary of the various results from immunological changes in blood and synovial tissue, the extension of the immune response from a diffuse myeloid to a lympho-myeloid inflammation appears to be associated with a more successful therapeutic response to biologics. With respect to advances in synovitis research, new targets for treatment against pathological subsets of immune cells or fibroblasts are already on the horizon. However, alternative strategies involving the microbiome may play an important role as well and research in this field is growing rapidly.

Current Approach to the Evaluation and Management of Septic Arthritis

Septic arthritis is an emergent condition caused by bacterial infection of a joint space. The most common etiology is hematogenous spread from bacteremia, but it can also occur from direct inoculation from bites, injection injuries, cellulitis, abscesses, or local trauma. Septic arthritis occurs most frequently in the lower extremities, with the hips and knees serving as the most common locations. The most sensitive findings include pain with motion of the joint, limited range of motion, tenderness of the joint, new joint swelling, and new effusion. Laboratory testing and imaging can support the diagnosis, but the criterion standard is diagnostic arthrocentesis. Treatment involves intravenous antibiotics and joint decompression.

Early diagnosis of septic arthritis in immunocompromised patients

OBJECTIVES

Septic arthritis results in rapid joint destruction if not properly diagnosed and treated. A work up for septic arthritis includes a peripheral white blood cell count, inflammatory markers, and a joint aspiration. In the general population, the interpretation of these labs has been well-defined by prior studies. To this point, no study has determined how immunosuppressive states affect this work up.

METHODS

Patients with immunosuppressive conditions who received a joint aspiration for a painful joint were retrospectively identified. Laboratory results from their work up were gathered and analyzed.

RESULTS

216 patients were included in the study, 21 of whom were diagnosed with septic arthritis. The average aspiration WBC count was 74,190 with 88% PMNs. 81% had a positive gram stain.

DISCUSSION

Laboratory values for immunosuppressed patients with septic arthritis were similar to those associated with septic arthritis in historical general population controls.

Evidence-based recommendations for the diagnosis and management of rheumatoid arthritis for non-rheumatologists: Integrating systematic literature research and expert opinion of the Thai Rheumatism Association

AIM

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease leading to joint damage, functional disability, poor quality of life and shortened life expectancy. Early diagnosis and aggressive treatment are a principal strategy to improve outcomes. To provide best practices in the diagnosis and management of patients with RA, the Thai Rheumatism Association (TRA) developed scientifically sound and clinically relevant evidence-based recommendations for general practitioners, internists, orthopedists, and physiatrists.

METHODS

Thirty-seven rheumatologists from across Thailand formulated 18 clinically relevant questions: three for diagnosis, 10 for treatments, four for monitoring, and one for referral. A bibliographic team systematically reviewed the relevant literature on these topics up to December 2013. A set of recommendations was proposed based on the results of systematic reviews combined with expert opinions. Group consensus was achieved for all statements and recommendations using the nominal group technique.

RESULTS

A set of recommendations was proposed. For diagnosis, either American College of Rheumatology (ACR) 1987 or ACR/European League Against Rheumatism 2010 classification criteria can be applied. For treatment, nonsteroidal anti-inflammatory drugs, glucocorticoid, and disease-modifying antirheumatic drugs, including antimalarials, methotrexate and sulfasalazine are recommended. Physiotherapy should be suggested to all patients. Tight control strategy and monitoring for efficacy and side effects of treatments, as well as indications for referral to a rheumatologist are provided.

CONCLUSIONS

These evidence-based recommendations provide practical guidance for diagnosis, fundamental management and referral of patients with RA for non-rheumatologists. However, it should be incorporated with clinical judgments and decisions about care for each individual patient.

Clinical significance of delta neutrophil index in the differential diagnosis between septic arthritis and acute gout attack within 24 hours after hospitalization

The most important differential diagnoses of acute monoarticular arthritis are septic arthritis and acute gout attack. Identifying infection is crucial in preventing the devastating outcome of septic arthritis. The delta neutrophil index (DNI) is a value that corresponds to the fraction of circulating immature granulocytes. As DNI reflects the burden of infection, we evaluated this index as a differentiating marker between septic arthritis and acute gout attack.The medical records of 149 patients with septic arthritis and 194 patients with acute gout attack were reviewed. A specific cell analyzer, ADVIA 2120, was used to measure DNI. Clinical and laboratory markers associated with predicting septic arthritis were assessed by using logistic regression.Patients with septic arthritis showed higher levels of DNI than those with acute gout attack (3.3 vs 0.6%, P < .001). Similar results were observed in patients without monosodium urate (MSU) crystal confirmation or those with normouricemia (3.3 vs 0.5 and 3.1 vs 0.7%, respectively; P < .001 for both). A DNI level of 1.9% was determined as the cutoff value for predicting septic arthritis. In the multivariate analysis, DNI was the most powerful independent value for predicting septic arthritis (odds ratio 14.003).This study showed the possibility of using DNI as a differentiating marker between septic arthritis and acute gout attack at the crucial early phase. DNI showed its relevance regardless of confirmation of MSU crystal deposition or serum level of uric acid.

Association between IL-17 and IgA in the joints of patients with inflammatory arthropathies

Background

Hyperactive secretion and pathogenic effects of interleukin (IL)-17 and IgA have been detected in different arthropathies. Recent evidence has revealed that T_H17 cytokines regulate mucosal IgA secretion. However, it is unknown whether and how IL-17 mediates synovial IgA production. Here we aim to investigate the connection of synovial IL-17 with IgA production in the joint.

In this study we included synovial fluids (SF) from patients with rheumatoid arthritis (RA; n = 66), spondyloarthritis (SpA; n = 18) and osteoarthritis (OA; n = 36). The levels of IL-17, IL-6, transforming growth factor (TGF)-β₁, B-cell-activating factor of the TNF family (BAFF) and anti-lipopolyssacharide (LPS) immunoglobulin (Ig)A were investigated by enzyme-linked immunosorbent assay (ELISA). Total IgA was measured by radial immunodiffusion assay. Synovial fluid-derived mononuclear cells (SFMC) were stimulated with bacterial antigens or SF-conditioned media, and cytokines and IgA were analyzed in the supernatants.

Results

IL-17, IL-6 and TGF-β₁ were increased in SF from both RA and SpA compared with OA patients. Concentration of IL-17 correlated with the disease activity score (DAS)-28, IL-6 and anti-LPS IgA levels. Bacterial-stimulated SFMCs from RA and SpA patients secreted higher IL-17 than vehicle-stimulated SFMCs. Conditioned media with SF containing IL-17 induced anti-LPS IgA production by SFMCs which was independent of IL-6 activity. Concentrations of synovial TGF-β₁ and BAFF correlated with anti-LPS and total IgA levels, respectively. Blockade of IL-17 decreased the production of TGF-β₁ and anti-LPS IgA by SF-stimulated SFMCs.

Conclusions

This study reports a connection between IL-17 and IgA secretion in the joint. In addition, it demonstrates that enterobacterial antigens trigger synovial IL-17 production, and that TGF-β₁ and BAFF may mediate the effect of IL-17 on IgA production. This circuit may contribute to the pathogenesis of inflammatory joint diseases.

Predictors of Septic Arthritis in the Adult Population

Septic arthritis is a devastating condition; well-established criteria for diagnosis exist in the pediatric population, but not for adults. This study evaluated patient factors and laboratory parameters that may be associated with the diagnosis of septic arthritis in adults. A total of 458 knee aspirates for suspected septic arthritis were evaluated with serum and synovial leukocyte counts and differentials as well as Kocher criteria for pediatric septic arthritis. Twenty-two patients (4.8%) had septic arthritis confirmed by a positive synovial fluid culture. Erythrocyte sedimentation rate (ESR) and serum white blood cell (WBC) counts were not statistically different between the 2 groups, with 64% of septic arthritis patients having a normal serum WBC count and 77% being afebrile. Mean synovial fluid WBC count was 26,758 cells/µL and 70,581 cells/µL in the nonseptic and septic groups, respectively. The likelihood ratio for a synovial fluid WBC count greater than 65,000 cells/µL was 2.8 (95% confidence interval, 1.2-6.7). Evaluation receiver operating characteristic curves using synovial WBC counts resulted in a significant area under the curve of 0.66 (P=.02). To achieve 90% specificity, a WBC cutoff of 64,000 cells/µL was required with a corresponding sensitivity of 40%. There was no significant difference in the synovial cell differential of 80% vs 90% in diagnosing infection. Synovial fluid WBC count greater than 64,000 cells/µL yielded the optimal combination of sensitivity and specificity. Polymorphonuclear leukocytes, ESR, serum WBC count, fever, and weight-bearing status were not significant predictors of septic arthritis. This study demonstrates the limited utility of Kocher criteria in the adult population and the importance of synovial leukocyte counts. [Orthopedics. 2016; 39(4):e657-e663.].

Synovial IL-6 as inflammatory marker in periprosthetic joint infections

We analyzed serum and synovial biomarkers of 69 patients. 31 of them suffered from a periprosthetic joint infection (PJI) and 38 from aseptic arthralgia after total joint arthroplasty. We used Receiver-Operating-Characteristic-curves to calculate the Area-under-the-curve (AUC), cutoff-values, positive (+LR), negative (-LR) and interval-Likelihood-Ratios (iLR) for predicting a PJI. The most significant parameter was synovial interleukin-6 (IL-6) (cutoff-value ≥ 30,750 pg/ml, AUC = 0.959, SE = 90.0%, SP = 94.7%, +LR = 17.27), followed by synovial lactate (cutoff-value ≥ 8.3 mmol/l, AUC = 0.844, SE = 71.4%, SP=88.0%, +LR = 5.95), and synovial glucose (cutoff-value ≤ 44 mg/dl, AUC = 0.829, SE = 79.2%, SP = 78.6%, +LR = 3.69). IL-6 ≥ 30,750 pg/ml and lactate ≥ 10 mmol/l make a PJI very likely, IL-6 <10,000pg/ml or lactate <4.3 mmol/l makes a PJI very unlikely. If none of these thresholds are met, physicians should use the iLR of IL-6, glucose and lactate to estimate the likelihood of PJI.

Characteristics of patients with definite septic arthritis at Hamad General Hospital, Qatar: a hospital-based study from 2006 to 2011

The aim of this retrospective study was to determine the epidemiological and clinical characteristics, coexisting conditions, causative organisms, and outcomes of all adult patients 15 years of age or older who had definite septic arthritis at Hamad General Hospital, Qatar, from 2006 to 2011. During this period, 56 patients were diagnosed with septic arthritis (mean age ± SD, 49.0 ± 16.6 years). In 53 of 56 (94.6%) patients, arthritis was diagnosed in a single joint, while polyarthritis was diagnosed in 3 of 56 (5.4%) patients; the most commonly involved joint was the knee (40 of 59 joints, 67.7%). The most frequent coexisting condition was diabetes mellitus (24 of 56 patients, 42.8%). Joint pain and restriction of movement were reported by all patients. Gram-positive bacteria accounted for 36 of all 57 (63.0%) isolated microorganisms, and Staphylococcus aureus was the most common pathogen (20 of 57 microorganisms, 35.0%). Three cases of tuberculous arthritis were seen. The most favored antibiotic combinations were cloxacillin/ciprofloxacin, cefazolin/ciprofloxacin, and vancomycin/ciprofloxacin. Repeated needle aspiration, open joint drainage, and arthroscopic techniques were performed in 18 (32.1%), 22 (39.3%), and 11 (19.6%) of the 56 patients, respectively. The 30-day mortality was 3.6%, and the remaining patients showed clinical improvement upon discharge. In conclusion, there was no specific sign or symptom for diagnosing septic arthritis. Isolation of bacteria from the synovial fluid confirmed the diagnosis, and S. aureus and streptococci were the most common pathogens isolated. Prompt treatment with appropriate antibiotics and synovial drainage are mandatory to improve the outcome.

Significance of Negative Cultures in the Treatment of Acute Hematogenous Bone and Joint Infections in Children

BACKGROUND

Synovial fluid and blood cultures often remain negative in acute bone and joint infections of childhood even when characteristic symptoms, signs, and/or radiologic proof are present.

METHODS

We analyzed 345 prospectively documented osteoarticular infections in children at age 3 months to 15 years. In 23% of the cases (N = 80), synovial, bone, and/or blood cultures remained negative. The characteristics of these cases were compared with patients with culture-positive bone and joint infections.

RESULTS

The 2 groups did not differ in age or gender distribution, surgical procedures performed, or outcome. In the culture-negative cases, the initial serum C-reactive protein level was lower (58 vs 87 mg/L, P < .0001) and the hospital stay was shorter (8 vs 11 days, P < .0001).

CONCLUSIONS

Bone and joint infections in which cultures fail to identify the causative agent can be treated similarly as culture-positive cases.

The fate of acutely inflamed joints with a negative synovial fluid culture

PURPOSE

The purpose of this study was to evaluate the management and fate of acutely inflamed joints with a negative synovial fluid culture.

METHODS

Between January and December 2009, all the patients who presented to our institution with an acutely inflamed joint and were subjected to microbiological assessment of their synovial fluid, were included in the study. Patients with a positive synovial fluid culture, a prosthetic joint replacement in situ and where an aspirate was obtained for a rheumatological diagnosis were excluded. This cohort was then divided into two groups depending on whether a diagnosis could be established through the course of their treatment. Group I included patients in whom a diagnosis could be established and group II included patients in whom a diagnosis could not be established. A thorough review of the patients' medical records and the hospital database was performed. Following this, a database consisting of the patient demographics, clinical features, investigations, treatment and outcome was created.

RESULTS

A total of 144 patients met the inclusion criteria (group I: 95, group II: 49). The most commonly affected joint in both the groups was the knee. The average time to presentation was shorter in group II. Clinical findings at presentation were comparable in both groups. However, inflammatory markers were more likely to be raised in group II in comparison with group I. Eighty-two percent of group II required antibiotic treatment compared with 15% of group I. The mean duration of antibiotic treatment in group I was ten days and in group II was 26 days. Mean hospital stay differed significantly between the two groups, with group II being more than twice as long as compared with group I (p=0.001). The rate of mortality was also higher in group II (8.2%, p=0.03).

CONCLUSION

Our study shows that patients presenting with an acutely inflamed joint and a negative synovial fluid culture in whom a diagnosis cannot be established during their hospital stay have a longer hospital stay and an increased rate of mortality as compared with patients in whom a diagnosis can be established.

Role of Newman's classification in predicting outcomes in patients with crystal arthritis

PURPOSE

The aim of the study was to evaluate the utility of Newman's classification in predicting outcomes in patients presenting with crystal arthritis.

METHODS

Between January and December 2009, all patients who presented to our institution with acute crystal arthritis and were investigated with microbiological assessment of their synovial fluid were included in the study. Patients were divided into two groups depending on the fulfilment of Newman's criteria for culture-negative septic arthritis. Group 1 included patients that fulfilled Newman's B criteria. Group 2 included patients that fulfilled Newman's C criteria. A database looking at the demographics, mode of presentation, investigations, treatment and outcomes was then established and the results compared between the two groups.

RESULTS

A total of 58 patients were identified (group 1: n = 13; group 2: n = 45). The average age was 71 years (range 33-96). The joint most commonly involved was the knee followed by the wrist. Clinical findings at presentation were comparable in both groups; however, WBC and C-reactive protein (CRP) were more likely to be raised in group 1. Although most patients in group 1 were treated with antibiotics (62%) there was still a higher rate of morbidity, greater use of supportive therapy and a longer hospital stay (22.3 days, SD 17.4) in comparison with group 2, where most patients were treated by observation only (76%, mean hospital stay 3.5 days, SD ± 4.4). The difference in length of hospital stay was statistically significant (p < 0.0001).

CONCLUSIONS

Newman's criteria are a good indicator for prognosis in patients with crystal arthritis. However, the presence of crystals in an acutely inflamed joint does not exclude the need for supportive therapy and long hospital stay even in the absence of positive synovial fluid culture.

Evidence-based diagnostics: adult septic arthritis

BACKGROUND

Acutely swollen or painful joints are common complaints in the emergency department (ED). Septic arthritis in adults is a challenging diagnosis, but prompt differentiation of a bacterial etiology is crucial to minimize morbidity and mortality.

OBJECTIVES

The objective was to perform a systematic review describing the diagnostic characteristics of history, physical examination, and bedside laboratory tests for nongonococcal septic arthritis. A secondary objective was to quantify test and treatment thresholds using derived estimates of sensitivity and specificity, as well as best-evidence diagnostic and treatment risks and anticipated benefits from appropriate therapy.

METHODS

Two electronic search engines (PUBMED and EMBASE) were used in conjunction with a selected bibliography and scientific abstract hand search. Inclusion criteria included adult trials of patients presenting with monoarticular complaints if they reported sufficient detail to reconstruct partial or complete 2 × 2 contingency tables for experimental diagnostic test characteristics using an acceptable criterion standard. Evidence was rated by two investigators using the Quality Assessment Tool for Diagnostic Accuracy Studies (QUADAS). When more than one similarly designed trial existed for a diagnostic test, meta-analysis was conducted using a random effects model. Interval likelihood ratios (LRs) were computed when possible. To illustrate one method to quantify theoretical points in the probability of disease whereby clinicians might cease testing altogether and either withhold treatment (test threshold) or initiate definitive therapy in lieu of further diagnostics (treatment threshold), an interactive spreadsheet was designed and sample calculations were provided based on research estimates of diagnostic accuracy, diagnostic risk, and therapeutic risk/benefits.

RESULTS

The prevalence of nongonococcal septic arthritis in ED patients with a single acutely painful joint is approximately 27% (95% confidence interval [CI] = 17% to 38%). With the exception of joint surgery (positive likelihood ratio [+LR] = 6.9) or skin infection overlying a prosthetic joint (+LR = 15.0), history, physical examination, and serum tests do not significantly alter posttest probability. Serum inflammatory markers such as white blood cell (WBC) counts, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) are not useful acutely. The interval LR for synovial white blood cell (sWBC) counts of 0 × 10(9)-25 × 10(9)/L was 0.33; for 25 × 10(9)-50 × 10(9)/L, 1.06; for 50 × 10(9)-100 × 10(9)/L, 3.59; and exceeding 100 × 10(9)/L, infinity. Synovial lactate may be useful to rule in or rule out the diagnosis of septic arthritis with a +LR ranging from 2.4 to infinity, and negative likelihood ratio (-LR) ranging from 0 to 0.46. Rapid polymerase chain reaction (PCR) of synovial fluid may identify the causative organism within 3 hours. Based on 56% sensitivity and 90% specificity for sWBC counts of >50 × 10(9)/L in conjunction with best-evidence estimates for diagnosis-related risk and treatment-related risk/benefit, the arthrocentesis test threshold is 5%, with a treatment threshold of 39%.

CONCLUSIONS

Recent joint surgery or cellulitis overlying a prosthetic hip or knee were the only findings on history or physical examination that significantly alter the probability of nongonococcal septic arthritis. Extreme values of sWBC (>50 × 10(9)/L) can increase, but not decrease, the probability of septic arthritis. Future ED-based diagnostic trials are needed to evaluate the role of clinical gestalt and the efficacy of nontraditional synovial markers such as lactate.

Diagnostic utility of laboratory tests in septic arthritis

BACKGROUND

Septic arthritis remains a challenging diagnosis in which the doctor often relies on laboratory tests.

OBJECTIVE

To examine the diagnostic utility of three ancillary tests--namely, white blood cells (WBC), erythrocyte sedimentation rate (ESR) and the WBC in the joint fluid (jWBC)--using likelihood ratios (LRs) and receiver operating characteristic (ROC) curves.

METHODS

This was a retrospective cohort study at the Jacobi Medical Center. Medical charts of patients who had undergone arthrocentesis were included. Patients who had "dry taps" were excluded from the study. Patients were considered to have septic arthritis if they had a positive arthrocentesis culture or operative findings. The primary outcomes of this study were the sensitivities, specificities, LR(+) and LR(-) values of the laboratory tests for septic arthritis. The performance characteristics of the laboratory tests were analysed using ROC curves.

RESULTS

156 patients were enrolled, 16 (10%) had septic arthritis. The sensitivities for WBC, ESR and jWBC were 0.75, 0.75 and 0.50, and the specificities were 0.55, 0.11 and 0.88, respectively. The LR(+) values were 1.7, 0.84 and 4.0, and the LR(-) values were 0.46, 2.4 and 0.57, respectively. In ROC curve analysis, jWBC was the best test (area under the curve (AUC) 0.75, 95% confidence interval (CI) 0.58 to 0.92), followed by WBC (AUC 0.69, 95% CI 0.57 to 0.80) and ESR (AUC 0.55, 95% CI 0.37 to 0.74). A cut-off of jWBC = 17 500 maximised sensitivity and specificity on the ROC curve.

CONCLUSIONS

jWBC was the best diagnostic test for septic arthritis, WBC and ESR were poor tests. However, no test was diagnostic, and the clinician must be careful with patients with a potential septic joint.

Laboratory tests in adults with monoarticular arthritis: can they rule out a septic joint?

It is difficult to differentiate septic arthritis from other causes of monoarticular arthritis solely with a history and physical examination. The clinician must rely on ancillary tests to make a diagnosis, such as the white blood cell count of peripheral blood (WBC), the erythrocyte sedimentation rate (ESR), and the white blood cell count of the joint fluid (jWBC) obtained from arthrocentesis. Although it is known that septic arthritis is associated with abnormalities in these tests, the majority of the data are based on studies in the pediatric population. In addition, although several emergency medicine texts indicate that a jWBC greater than 50,000 cells/mm(3) is "positive," it is known that septic arthritis can occur in patients with low jWBCs.

OBJECTIVES

To determine whether specific ancillary tests have sufficiently high sensitivities to rule out septic arthritis in adults.

METHODS

This was a retrospective consecutive case series of patients from an urban emergency department (ED). Patients at least 18 years old who had septic arthritis confirmed by positive arthrocentesis culture or operative findings were included in the study. WBC greater than 11,000 cells/mm(3), ESR greater than 30 mm/hr, and jWBC greater than 50,000 cells/mm(3) were considered elevated.

RESULTS

Seventy-three patients met the inclusion criteria. The sensitivities of an elevated WBC, ESR, or jWBC in adults who had septic arthritis were 48%, 96%, and 64%, respectively. There were broad ranges of WBC, ESR, or jWBC among the patients. More than one third of adult patients with septic arthritis had jWBCs less than 50,000 cells/mm(3). All patients had an abnormality in at least one of these tests.

CONCLUSIONS

The WBC, ESR, and jWBC are extremely variable in adults with septic arthritis. Laboratory tests do not rule out septic arthritis with accuracy.

The value of white blood cell counts before revision total knee arthroplasty

A white blood cell count (WBC) of >50000 cell/mm(3) from a knee aspirate with >or=80% polymorphonuclear cells (PMNCs) is suggestive of infection. This study sought to determine if these same criteria were applicable when interpreting aspirates from a total knee. Of 440 revision total knee arthroplasties, 86 patients had preoperative aspirations of the knee before revision. Fifty-five aspirates were from aseptic failures; 31 aspirates were from patients determined to have septic failure. The mean white blood cell (WBC) count in aspirates from the aseptic group was 645 cells/mm(3) (SD = 878). The mean WBC count in the septic group was 25951 cells/mm(3) (SD = 34994; P=<.001). The mean percentage of PMNCs was statistically higher in the septic group compared with the aseptic group (72.8% vs 27.3%; P=<.001). The synovial fluid WBC count differential analysis is a statistically relevant indicator of the presence or absence of infection in revision knee arthroplasty. Aspirates with a WBC count of 2500 per milliliter and 60% PMNCs are highly suggestive of infection.

White blood cell counts and differential in synovial fluid of aseptically failed total knee arthroplasty

A cell count and differential was obtained on synovial fluid samples from 79 total knee arthroplasties undergoing revision for aseptic failure over a 5-year period. The mean white blood cell count (WBC) was 782/mL (range, 11-7,200/mL). The mean percentage of monocyte cells was 87%, and the mean polymorphonuclear leukocyte (PML) cell count was 13%. Eight patients (10.4%) had leukocyte cell counts >2,000. Five knees in 4 patients with rheumatoid arthritis had PML counts >50%. There was a single postoperative infection. In patients with osteoarthritis as a primary diagnosis, a synovial WBC of <2,000 and a differential with <50% PMLs had a 98% negative predictive value for the absence of infection. Key words: synovial fluid, cell count and differential, failed total knee arthroplasty, revision total knee arthroplasty.

Two forms of reactive arthritis?

Inflammatory arthritides developing after a distant infection have so far been called reactive or postinfectious, quite often depending on the microbial trigger and/or HLA-B27 status of the patient. For clarity, it is proposed that they all should be called reactive arthritis, which, according to the trigger, occurs as an HLA-B27 associated or non-associated form. In addition to the causative agents and HLA-B27, these two categories are also distinguished by other characteristics. Most important, HLA-B27 associated arthritis may occur identical to the Reiter's syndrome with accompanying ureteritis and/or conjunctivitis, whereas in the B27 non-associated form this has not been clearly described. Likewise, only the B27 associated form belongs to the group of spondyloarthropathies.

Prospective analysis of preoperative and intraoperative investigations for the diagnosis of infection at the sites of two hundred and two revision total hip arthroplasties

BACKGROUND

Total hip arthroplasty is a commonly performed procedure in the United States and Canada that is associated with a definite risk of postoperative infection. Moreover, diagnosing an infection after total hip arthroplasty can present a challenge as there are no preoperative tests that are consistently sensitive and specific for infection in patients who need a revision arthroplasty. The present prospective study was performed to evaluate a variety of investigations for the diagnosis of infection at the site of a previous arthroplasty in order to determine if any combination of diagnostic studies could be used to determine which patients are at risk for a postoperative wound infection.

METHODS

We prospectively analyzed the preoperative and intraoperative investigations used for the diagnosis of infection in 178 patients who had a total of 202 revision hip replacements. Clinical data were collected preoperatively. Investigations to determine the presence or absence of infection included a white blood-cell count, measurement of the erythrocyte sedimentation rate, measurement of the level of C-reactive protein, preoperative aspiration of the joint, intraoperative gram-staining and culture of periprosthetic tissue, a white blood-cell count in synovial fluid, and examination of intraoperative frozen sections. Frozen sections were analyzed in a blinded fashion without knowledge of clinical or laboratory data. Patients receiving antibiotics at the time of aspiration or collection of specimens for intraoperative culture were excluded from the analysis of those investigations, regardless of the results of the cultures. A positive result (suggestive of infection) was clearly defined for each of the investigations.

RESULTS

Thirty-five hips (17 percent) were determined to be infected on the basis of clinical findings and positive results, according to the defined criteria, of investigations. With inflammatory conditions excluded, the sensitivity, specificity, positive predictive value, and negative predictive value were 0.82, 0.85, 0.58, and 0.95, respectively, for the erythrocyte sedimentation rate and 0.96, 0.92, 0.74, and 0.99, respectively, for the level of C-reactive protein. All patients who had a periprosthetic infection had an elevated erythrocyte sedimentation rate or level of C-reactive protein, but not always both. When patients who were receiving antibiotics were excluded, the results of aspiration of the joint were 0.86 for sensitivity, 0.94 for specificity, 0.67 for the positive predictive value, and 0.98 for the negative predictive value. Intraoperative studies revealed sensitivities, specificities, positive predictive values, and negative predictive values of 0.19, 0.98, 0.63, and 0.89, respectively, for gram-staining of specimens of the most inflamed-appearing tissue; 0.36, 0.99, 0.91, and 0.90, respectively, for the white bloodcell count in synovial fluid; and 0.89, 0.85, 0.52, and 0.98, respectively, for a neutrophil count in synovial fluid of more than 80 percent. The sensitivity, specificity, positive predictive value, and negative predictive value were 0.80, 0.94, 0.74, and 0.96, respectively, for the frozen sections and 0.94, 0.97, 0.77, and 0.99, respectively, for the intraoperative cultures.

CONCLUSIONS

The combination of a normal erythrocyte sedimentation rate and C-reactive protein level is reliable for predicting the absence of infection. Aspiration should be used when the erythrocyte sedimentation rate or the C-reactive protein level is elevated or when a clinical suspicion of infection remains. We found the gram stain to be unreliable. Examination of intraoperative frozen sections is useful in equivocal cases or when hematological markers may be falsely elevated because of an inflammatory or other condition.

Occurrence of HLA-B27 tissue antigen in patients with purulent arthritis caused by Staphylococcus aureus or beta-haemolytic streptococci

The HLA-B27 tissue antigen is associated with reactive arthritis caused by different bacterial infections but its occurrence in purulent arthritis has not been studied earlier. We analysed the frequency of HLA-B27 in patients with culture proven purulent arthritis caused by Staphylococcus aureus or beta-haemolytic streptococci. The study included 41 patients treated during the years 1979-96 (15 female and 26 male) with a mean age of 52 years (range 16-80 years). HLA-B27 was found in 24% (9/37) of the tested patients compared with 14% in the healthy Finnish population, but the difference was not statistically significant (P < 0.50). No statistical difference in disease activity according to febrile days or duration of the disease could be found between HLA-B27 positive and negative patients. We conclude that HLA-B27 is not a risk factor for purulent arthritis, and when present it has no significant modifying effect on the clinical picture of purulent arthritis.

Expression of human group II phospholipase A2 in transgenic mice

Group II phospholipase A2 (PLA2) has been proposed to play an important role in inflammation and defense against bacterial infection. We investigated tissues of transgenic mice expressing the human group II PLA2 gene by immunohistochemistry using rabbit anti-human group II PLA2 antibodies, and by in situ hybridization by probing with human group II PLA2 mRNA anti-sense (test) and sense (control) riboprobes. By immunohistochemistry, human group II PLA2 was found in various mouse tissues and cell types including hepatocytes, proximal tubule cells of the kidney, epithelial cells of the renal pelvis, urinary bladder and ureter, granulosa cells of Graafian follicles, aortic intima and media, cartilage, epiphyseal bone, bronchial epithelial cells, and connective tissue cells in the dermis. By in situ hybridization, group II PLA2 mRNA was localized in hepatocytes, epidermal cells, dermal cells, connective tissue fibroblasts, epithelial and smooth muscle cells of the urinary bladder, and cells of Bowman's capsule. These results show that human group II PLA2 is expressed in large amounts in hepatocytes and many extrahepatic tissues of the transgenic mice. These animals provide a useful new tool for studies on the metabolism, in vivo effects, and physiological and pathological roles of phospholipase A2.

Arthritis patient as an emergency case at a university hospital

During a 6-month period in 1994-1995, 0.7% of patient visits (51 visits of 47 patients) at the emergency unit of the Department of Medicine, Helsinki University Central Hospital, were due to joint symptoms. Infection seemed to play an important role as the etiologic factor for the joint complaints. Acute joint exacerbation in pre-existing arthritis was the reason for 11.7%, and suspected Baker's cyst for 3.9% of the visits. Confirmed (12.8%) or suspected reactive arthritis (10.6%), septic arthritis/spondylitis (6.4%), arthritis with inflammatory bowel disease (6.4%), and gout (14.9%) were the most common final diagnoses for the patients. In a quarter of the patients, the etiology for joint symptoms could not be confirmed. In conclusion, joint symptoms very seldom lead to visits to an emergency unit. In such cases, infection seems to be an important contributing factor. Patients with chronic rheumatic diseases only occasionally have to seek help at an emergency unit.

An 18 year clinical review of septic arthritis from tropical Australia

A retrospective study of 191 cases of septic arthritis was undertaken at Royal Darwin Hospital in the tropical north of Australia. Incidence was 9.2 per 100,000 overall and 29.1 per 100,000 in Aboriginal Australians (RR 6.6; 95% CI 5.0-8.9). Males were affected more than females (RR 1.6; 95% CI 1.2-2.1). There was no previous joint disease or medical illness in 54%. The commonest joints involved were the knee (54%) and hip (13%). Significant age associations were infected hips in those under 15 years and infected knees in those over 45 years. Seventy two percent of infections were haematogenous. Causative organisms included Staphylococcus aureus (37%), Streptococcus pyogenes (16%) and Neisseria gonorrhoeae (12%). Unusual infections included three melioidosis cases. Polyarthritis occurred in 17%, with N. gonorrhoeae (11/23) more likely to present as polyarthritis than other organisms (22/168) (OR 6.0; 95% CI 2.1-16.7). Univariate and multivariate analysis showed the hip to be at greater risk for S. aureus than other joints. Open arthrotomy was a more successful treatment procedure than arthroscopic washout or needle aspiration.

The spondyloarthropathies

The spondyloarthropathies occur with variable frequency in the tropics. Ankylosing spondylitis, in particular, is thought to be rare in tropical Africa, reflecting a low frequency of the HLA B27 gene. However, in the Melanesian populations of Papua New Guinea where there is a relatively high frequency of HLA B27, ankylosing spondylosis is infrequent. These diverse observations may be related to variations in B27 sub-types. Reactive arthritis is a common and important form of acute arthritis in the tropics and in Papua New Guinea at least has a strong association with HLA B27. In Africa an increasing prevalence of reactive arthritis may be related to the spread of HIV infection. Extra-articular features such as balanitis and enthositis are helpful pointers to the diagnosis. Disseminated gonococcal infection and tuberculosis must always be considered and treatment offered if doubt exists. The mainstay of treatment of reactive arthritis is, as always, an anti-inflammatory drug, supplemented by hydrocortisone injections; docycline is available for chlamydia-triggered arthritis and chloroquine or dapsone for more chronic, unresponsive cases.

Listeria monocytogenes arthritis of several joints

A patient with rheumatoid arthritis (RA) developed an infection caused by Listeria monocytogenes in her left knee and both shoulder joints. The clinical presentation of the disease was rather indolent with relatively moderate joint symptoms. Moreover, the synovial fluid sample was only slightly turbid with a white blood cell count of 23.5 x 10(9)/1. As compared to the earlier reported cases of L. monocytogenes septic arthritis, our patient is unique because she had infection in several joints. The polyarticular joint involvement combined with the clinical symptoms resembling the activation of RA posed us diagnostic difficulties.

Infection and arthritis

Reactive arthritis is caused by an infection, and components of the triggering agent can be demonstrated at the site of inflammation. This fact has opened new views in studies regarding other rheumatic diseases, such as rheumatoid arthritis and ankylosing spondylitis. The possible role of infectious agents in their etiology and pathogenesis is being re-evaluated.

Synovial-fluid D-lactic acid in bacterial and other acute joint effusions

The use of D-lactic acid in differential diagnosis of bacterial arthritis was evaluated in a prospective study. The concentration of D-lactic acid was determined by the enzymatic UV-method in sixty-eight synovial fluids (SF) and in twenty four sera from adult patients with acute knee effusion. High concentrations of D-lactic acid (> 0.15 mmol/l) were measured most frequently in SF from bacterial arthritis, but also in individual culture-negative SF samples from patients with inflammatory culture-negative joint effusions with and without identified history of infections. Determination of SF D-lactic acid is not useful in differential diagnosis of bacterial arthritis.