How sensitive is the synovial fluid white blood cell count in diagnosing septic arthritis?

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.

Utility of Synovial Fluid Biomarkers for Culture-Positive Septic Arthritis in a Lyme Disease-Endemic Region

OBJECTIVE

To evaluate the performance of synovial fluid biomarkers to identify children with culture-positive septic arthritis.

METHODS

We identified children 6 months to 18 years old presenting to a single emergency department between 2007 and 2022 undergoing evaluation for septic arthritis defined by having a synovial fluid culture obtained. Our primary outcome was septic arthritis defined by a positive synovial fluid culture. We evaluated the ability of synovial fluid biomarkers to identify children with septic arthritis using area under the receiver operating characteristic curve (AUC) analyses. We measured the sensitivity and specificity of commonly used synovial fluid biomarkers.

RESULTS

We included 796 children, of whom 79 (10%) had septic arthritis. Compared with synovial white blood cell count (AUC, 0.72; 95% confidence interval [CI], 0.65-0.78), absolute neutrophil count (AUC, 0.72; 95% CI, 0.66-0.79; P = 0.09), percent neutrophils (AUC, 0.66; 95% CI, 0.60-0.71; P = 0.12), and glucose (AUC, 0.78; 95% CI, 0.67-0.90; P = 0.33) performed similarly, whereas protein (AUC, 0.52; 95% CI, 0.40-0.63, P = 0.04) had lower diagnostic accuracy. Synovial fluid white blood cell count ≥50,000 cells/μL had a sensitivity of 62.0% (95% CI, 50.4%-72.7%) and a specificity of 67.0% (95% CI, 63.4%-70.4%), whereas a positive synovial fluid Gram stain had a sensitivity of 48.1% (95% CI, 36.5%-59.7%) and specificity of 99.1% (95% CI, 98.1%-99.7%) for septic arthritis.

CONCLUSIONS

None of the routinely available synovial fluid biomarkers had sufficient accuracy to be used in isolation in the identification of children with septic arthritis. New approaches including multivariate clinical prediction rules and novel biomarkers are needed.

Diagnostic considerations in the clinical management of sudden swelling of the knee: a case report and review of the literature

BACKGROUND

Reactive arthritis and septic arthritis rarely present concomitantly in the same joint and patient. Reactive arthritis presenting after coronavirus disease 2019 is also exceedingly rare, with less than 30 cases reported thus far. Less common pathogens such as Clostridium difficile have been reported to cause reactive arthritis, especially in patients with a positive human leukocyte antigen B27, and therefore should be considered in diagnostic algorithms. The aim of this case report is to highlight the difficulties and precautions in discerning and diagnosing patients presenting with sudden swelling of the knee.

CASE PRESENTATION

We report the case of a 70-year-old Caucasian male with a recent history of coronavirus disease 2019 upper respiratory infection and diarrhea and negating trauma, who presented with a swollen and painful knee. Pain and swelling worsened and inflammatory parameters increased after an intraarticular corticosteroid injection. The patient was therefore treated with arthroscopic lavage and intravenous antibiotics for suspected septic arthritis. Synovial fluid and synovium samples were taken and sent for microbiological analysis. Synovial fluid cytology showed increased leukocytes at 10,980 × 106/L, while polymerase chain reaction and cultures came back sterile. Clostridium difficile toxin was later detected from a stool sample and the patient was treated with oral vancomycin. The patient was tested for the presence of human leukocyte antigen B27, which was positive. We present a review of the literature about the challenges of distinguishing septic from reactive arthritis, and about the mechanisms that predispose certain patients to this rheumatological disease.

CONCLUSIONS

It is still a challenge to differentiate between septic and reactive arthritis of the knee, and it is even more challenging to identify the exact cause of reactive arthritis. This case report of a human leukocyte antigen-B27-positive patient highlights the necessity of contemplating different, less common causes of a swollen knee joint as a differential diagnosis of an apparent septic infection, especially in the coronavirus disease 2019 era. Treating the patient for septic arthritis prevented any possible complications of such a condition, while treating the C. difficile infection contributed to the substantial relief of symptoms.

Effect of Antibiotic Administration Before Joint Aspiration on Synovial Fluid White Blood Cell Count in Native Joint Septic Arthritis

Background

This study was performed to assess the impact of preaspiration antibiotics on synovial fluid analysis and timing of operative treatment in native-joint septic arthritis.

Methods

We performed a retrospective record review of adult patients from an urban level 1 trauma center with native joint septic arthritis in 2015-2019, identified by means of codes from the International Classification of Diseases (Ninth Revision and Tenth Revision). Univariate and multivariate analyses were performed to determine whether antibiotics were associated with lower synovial fluid white blood cell counts (WBCs), the percentage of polymorphonuclear neutrophil (PMNs), and rate of culture positivity. Secondary analysis included time elapsed from aspiration to surgery.

Results

Of the 126 patients with septic joints included, nearly two-thirds (n = 80 [63.5%]) received antibiotics before joint aspiration. The synovial fluid WBC count, percentage of PMNs, and rate of culture positivity were significantly lower in patients who received preaspiration antibiotics than in those who did not (mean WBC count, 51 379.1/μL [standard deviation, 52 576.3/μL] vs 92 162.7/μL [59 330.6/μL], respectively [P < .001]; PMN percentage, 83.6% [20.5%] vs 91.9% [6.0%; P = .01]; and culture positivity, 32.5% vs 59.1% [P = .008]). Multivariable analyses revealed that these associations remained after controlling for potential confounders (change in PMNs, -42 784.60/μL [95% confidence interval, -65 355/μL to -20 213.90/μL [P < .001]; change in PMNs, -7.8% [-13.7% to -1.8%] [P = .01]; odds ratio, 0.39 [.18-.87; P = .02). Patients with a synovial fluid WBC count ≤50 000/μL experienced significant delay in time from joint aspiration to operative intervention (mean [standard deviation], 10.5 [11.3] vs 17.9 [17.2] hours; P = .02).

Conclusions

The administration of antibiotics before joint aspiration for suspected septic arthritis appears to decrease the synovial fluid WBC count, the percentage of PMNs, and the rate of culture positivity. Efforts to limit antibiotic administration before joint aspiration are important to minimize diagnostic dilemmas and circumvent treatment delays.

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.

A 64-Year-Old Man with Joint Pain

A 64-Year-Old Man with Joint PainA 64-year-old man presented for evaluation of acute oligoarticular joint pain. How do you approach the evaluation, and what is the diagnosis?

Assessment and diagnosis of the acute hot joint: a systematic review and meta-analysis

OBJECTIVES

Prompt diagnosis of septic arthritis (SA) in acute native hot joints is essential for avoiding unnecessary antibiotics and hospital admissions. We evaluated the utility of synovial fluid (SF) and serum tests in differentiating causes of acute hot joints.

METHODS

We performed a systematic literature review of diagnostic testing for acute hot joints. Articles were included if studying ≥1 serum or SF test(s) for an acute hot joint, compared with clinical assessment and SF microscopy and culture. English-language articles only were included, without date restriction. The following were recorded for each test, threshold and diagnosis: sensitivity, specificity, positive/negative predictive values and likelihood ratios. For directly comparable tests (i.e. identical fluid, test and threshold), bivariate random-effects meta-analysis was used to pool sensitivity, specificity, and areas under the curves.

RESULTS

A total of 8443 articles were identified, and 49 were ultimately included. Information on 28 distinct markers in SF and serum, differentiating septic from non-septic joints, was extracted. Most had been tested at multiple diagnostic thresholds, yielding a total of 27 serum markers and 156 SF markers. Due to heterogeneity of study design, outcomes and thresholds, meta-analysis was possible for only eight SF tests, all differentiating septic from non-septic joints. Of these, leucocyte esterase had the highest pooled sensitivity [0.94 (0.70, 0.99)] with good pooled specificity [0.74 (0.67, 0.81)].

CONCLUSION

Our review demonstrates many single tests, individually with diagnostic utility but suboptimal accuracy for exclusion of native joint infection. A combination of several tests with or without a stratification score is required for optimizing rapid assessment of the hot joint.

Performance of a diagnostic score for gouty arthritis: results from a cohort of acute arthritis suspected of being septic

Septic arthritis (SA) and gout are the main suspected etiologies of acute monoarthritis. Differentiating them is essential because SA is an emergency. The performance of a gout diagnostic score developed by Janssens et al. was investigated in a cohort of patients with acute arthritis suspected of being septic. This was an ancillary study of a single-center cohort of patients with suspected SA. Patients were classified into three groups according to the final diagnosis (gout, SA or other diagnosis). We assessed the performance of the score (sensitivity [Se], specificity [Sp], positive and negative predictive value [PPV, NPV], area under the receiver operating characteristic [ROC] curve) for the diagnosis of gouty arthritis. In total, 138 patients were included: 28 (20.3%) had gout, 42 (30.4%) SA, and 68 (49.3%) another diagnosis. The median diagnostic score was 7.0 [4.5; 8.8] for patients with gout, 3.5 [2.5; 6.0] for those with SA and 3.0 [2.0-5.0] for those with another diagnosis. With a score threshold of ≥ 8, the Se for a diagnosis of gout was 28.6%, Sp 96.4%, PPV 66.7%, and NPV 84.1%. With a threshold of ≤ 4, the Se was 82.1%, Sp 64.5%, PPV 37.1%, and NPV 93.4%. The area under the ROC for the diagnostic score was 0.79. The performance of the clinico-biological score of Janssens et al. for a diagnosis of gout applied to a cohort of patients with acute arthritis and suspected of being septic was poor. Joint aspiration remains necessary to differentiate SA from another etiology.

Diagnostic Utility of Synovial Fluid Cell Counts and CRP in Pediatric Knee Arthritis: A 10-Year Monocentric, Retrospective Study

Background: Orthopedic surgeons often use the intra-articular white blood counts (WBCs) and the percentage of polymorphonuclear cells (PMN) in the diagnosis of an acute swollen and painful knee joint in children. Today, there is no established threshold for the synovial WBC, and their differentiation, as indicative of native joint knee bacterial arthritis. We determine the sensitivity and specificity of synovial WBCs and PMN percentages in the prediction of a community-acquired, acute bacterial native joint septic arthritis (SA) in the pediatric population. Methods: A retrospective study on healthy children 0–16 years of age who underwent knee joint aspiration for a community-acquired, acute irritable knee effusion in our tertiary-care children’s hospital between May 2009 and April 2019 was conducted. We divided the study population into two groups according to the detection of bacterial arthritis in the synovial fluid (bacterial arthritis versus its absence) and compared the intra-articular leukocyte and C-reactive protein (CRP) levels. Results: Overall, we found a statistically significant difference regarding the total CRP (p = 0.017), leukocyte or PMN counts (p ≤ 0.001 in favor of a bacterial arthritis). In contrast, the percentage of the neutrophils was not determinant for the later confirmation of bacterial pathogens, and we were unable to establish diagnostically determining minimal thresholds of the intra-articular CRP and leukocyte levels. Conclusions: This pilot study suggests that either the leukocyte or PMN counts may be associated with a bacterial origin of knee arthritis in children. We plan a larger prospective interventional study in the future to confirm these findings including the investigation of other joint aspirate biomarkers.

Optimal Synovial Fluid Leukocyte Count Cutoff for Diagnosing Native Joint Septic Arthritis After Antibiotics: A Receiver Operating Characteristic Analysis of Accuracy

INTRODUCTION

Urgent treatment of septic arthritis is key in preventing devastating morbidity or mortality. Accurate diagnosis is critical, and the standard diagnostic cutoff of 50,000 synovial leukocytes may be altered by previous administration of antibiotics. Our objective was to identify and compare a cutoff synovial leukocyte count with a high sensitivity and specificity for diagnosis of septic arthritis in patients who received antibiotics and those who had not. A receiver operating characteristic (ROC) curve was used to provide a discriminate cutoff value for diagnosing septic arthritis.

METHODS

A retrospective chart review of 383 patients was done over a 13-year period including those who had arthrocentesis of any joint. Two groups were created, those who had not been given antibiotics within 2 weeks (control) and those who received intravenous or oral antibiotics within 2 weeks before arthrocentesis. Relevant data included synovial leukocyte count and differential cell count. Additional metrics included temperature, erythrocyte sedimentation rate, and C-reactive protein. A ROC curve determined the optimal synovial white blood cell cutoff for diagnosing septic arthritis in native joints for each group.

RESULTS

The ROC curve determined that patients who received antibiotics had an optimal cutoff of >16,000 cells (sensitivity = 82%, specificity = 76%), and a neutrophil percentage cutoff of >90% (sensitivity = 73%, specificity = 74%). The control group had an optimal synovial leukocyte cutoff of >33,000 cells (sensitivity = 96%, specificity = 95%). The optimal neutrophil percentage cutoff in the control group was >83% neutrophils (sensitivity = 89%, specificity = 79%).

CONCLUSION

When a patient is given antibiotics before arthrocentesis, a diagnostic value of >16,000 synovial leukocytes should be used to guide treatment of septic arthritis. A diagnostic value of >33,000 synovial leukocytes yields the highest accuracy for diagnosis of septic arthritis in patients who have not been given antibiotics before arthrocentesis.

LEVEL OF EVIDENCE

III.

The Diagnostic Value of Synovial Fluid Lymphocytes in Gout Patients

Objective

This study is aimed at investigating the diagnostic value of synovial fluid cell counts in gout patients.

Methods

A total of 185 gout, 64 rheumatoid arthritis (RA), 26 axial spondyloarthritis (axSpA), and 24 osteoarthritis (OA) patients were included in the study. According to serum uric acid (sUA) levels on attack, gout patients were divided into normal sUA gout patients and high sUA gout patients. The laboratory data were recorded. ROC curves were generated to evaluate the diagnostic value of the variables for gout patients and normal sUA gout patients compared with RA, axSpA, and OA patients.

Results

The synovial fluid white blood cell (WBC), peripheral blood mononuclear cell (PBMC), monocyte, polymorphonuclear (PMN), and neutrophil counts in gout patients were higher than those in OA patients (P < 0.05). The synovial fluid PBMC and lymphocyte counts in gout patients were lower than those in RA and axSpA patients (P < 0.05). ROC curve results showed that the AUC values of lymphocytes and sUA for gout patients were 0.728 and 0.881, respectively, which were higher than those of other variables. The optimal cutoff value of lymphocytes for gout was 1.362, with a Youden index of 0.439, a sensitivity of 83.3%, and a specificity of 60.6%. The AUC values of lymphocytes, sUA, and CRP for normal sUA gout patients were 0.694, 0.643, and 0.700, respectively, which were higher than those of other variables. The optimal cutoff value of lymphocytes for normal sUA gout patients was 1.362, with a Youden index of 0.422, a sensitivity of 81.6%, and a specificity of 60.6%.

Conclusions

The synovial fluid cell counts of gout patients were different from those of RA, axSpA, and OA patients. Synovial fluid lymphocytes had a higher diagnostic value for gout.

Detection of bacterial DNA in synovial fluid in dogs with arthritis: a comparison between bacterial culture and 16S rRNA polymerase chain reaction

Background

Septic arthritis (SA) is a serious condition in dogs that requires a prompt diagnosis and treatment to minimize long-term joint pathology. Although bacterial detection in synovial fluid (SF) through culture or cytology is often performed to confirm diagnosis, the sensitivity of these tests is low. The need for a reliable diagnostic tool to confirm the presence of bacteria in SF in humans has led to the increased use of 16S rRNA (i.e., ribosomal RNA) gene sequencing by polymerase chain reaction (16S rRNA PCR). The aim of this prospective clinical study was to compare the sensitivity and specificity of 16S rRNA PCR with bacterial culture on blood agar plates after pre-incubation of SF in paediatric blood bacterial culture bottles to identify bacteria in dogs with clinical signs of SA and to investigate the usefulness of these methods as diagnostic tools.

Results

Ten dogs with clinical signs of SA, nine with osteoarthritis (OA, control group) and nine with clinical signs of immune-mediated polyarthritis (IMPA, second control group) were examined. Bacterial culture was positive in seven of 10 dogs with clinical SA, of which only two were positive by 16S rRNA PCR. The sensitivity of 16S rRNA PCR and bacterial culture analysis for dogs with clinical SA were 20% and 70%, respectively. All SF samples collected from control group (n = 9) and second control group (n = 14) animals were negative on culture, and 16S rRNA PCR rendered a specificity of 100%.

Conclusions

Our study showed a lower sensitivity of 16S rRNA PCR than bacterial culture for dogs with clinical SA. Our findings suggest that there is currently no advantage in using 16S rRNA PCR as a diagnostic tool for dogs with clinical SA. Furthermore, our study indicates that pre-incubation in paediatric blood bacterial culture bottles before bacterial cultivation on blood agar plates might enhance bacterial culture sensitivity compared to other culture methods.

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.

Approach to a patient with monoarticular disease

PURPOSE

To reassess the diagnostic approach to a patient with a monoarticular disease in light of the up-to-date medical literature and to examine the practical utility of traditional and newer imaging tools in the setting of monoarthritis.

RESULTS

The monoarticular disease can represent a medical emergency on the one hand and be a diagnostic conundrum on the other. The management rules of patients with monoarthritis have been established long ago, but various pitfalls still lead physicians off the right diagnosis at times. Septic, pseudoseptic arthritis and hemarthrosis are the most common diagnoses made in patients with an acute presentation, and a decision not to perform a diagnostic arthrocentesis is the most prevalent cause of misdiagnosis in this setting. Many rheumatic and infectious diseases can present with more indolent monoarthritis; careful history and physical examination frequently provide clues to the straightforward diagnosis in some cases, but the extensive investigation is needed in others. Imaging methods become indispensable in individuals with the non-inflammatory monoarticular disease, with magnetic resonance imaging being the gold standard for diagnosing pigmented villonodular synovitis, lipoma arborescence, avascular necrosis, or neuropathic arthropathy.

CONCLUSIONS

A great variety of medical disorders can present as a monoarticular disease. The disease presentation dictates different diagnostic behavior, while knowing the available imaging methods' diagnostic potential should further shorten the diagnostic process.

Pediatric Septic Arthritis of the Knee Due to a Multi-Sensitive Streptococcus pyogenes Strain Responsive to Clindamycin-A Case Report

Septic arthritis is an inflammatory process usually generated by a bacterial infection. The knee is one of the most frequently involved joints. The etiology varies depending on age, and hematogenous spread remains the primary cause in children. Herein, we report a case of a previously healthy three-year-old female who was referred to our institution for acute swelling of her right knee. After a clinical and radiological diagnosis of septic arthritis, an empirical treatment with a combination of cefotaxime and clindamycin was initiated. The isolation of a multi-sensitive Streptococcus pyogenes strain from the joint’s effusion prompted the discontinuation of clindamycin and the usage of cefotaxime alone. One week later, an ultrasound was executed due to worsening in the patient’s clinical conditions, and an organized corpuscular intra-articular effusion with diffuse synovial thickening was revealed. Cefotaxime was therefore replaced with clindamycin, which improved the symptoms. Despite the antibiotic sensitivity test having revealed a microorganism with sensitivity to both cephalosporin and clindamycin, clinical resistance to cefotaxime was encountered and a shift in the antimicrobial treatment was necessary to ensure a full recovery. This case study confirms that an antibiotic regimen based solely on a susceptibility test may be ineffective for such cases.

A narrative review of the last decade's literature on the diagnostic accuracy of septic arthritis of the native joint

While septic arthritis can be a straightforward diagnosis, there are many cases when the diagnosis is difficult to make. The aim of this study was to review the last decade’s literature on the diagnosis of septic arthritis of the native joint in adults and summarize that data in an easy to follow algorithm to clarify how the last decade’s data may be applied to the diagnosis of septic arthritis. A search of PubMed and CINAHL databases was performed to identify studies that compared results diagnostic tests for septic arthritis. We cross referenced this search with searches of additional databases (including Cochrane Library and Scopus) to confirm similar search results. The Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool was used by two independent reviewers to determine study quality and risk of bias. After applying inclusion and exclusion criteria to the initial search, 15 papers total were included for analysis. All 15 papers were of high quality methodology as determined by the QUADAS tool. There were 26 different diagnostics tests used across the 15 papers included for review. Three of those diagnostic tests had specificity and sensitivity greater than 80%. Eight tests had a positive likelihood ratio of ≥10. Three tests had a negative likelihood ratio < 0.1, indicating that they may help to rule out septic arthritis. A flowchart was created to summarize the findings of our review, so that physicians may reference this visual in making the appropriate diagnosis when the commonly held standards of cell count, gram stain, and culture aren’t enough to make the diagnosis.

Evaluation for septic arthritis of the native adult knee is aided by multivariable assessment

INTRODUCTION

Evaluation of suspected septic arthritis of the native adult knee is a common diagnostic dilemma. Pre-aspirate criteria predictive of septic arthritis do not exist for the adult knee and investigations of aspiration results (cell count, differential, gram stain and crystal analysis) have been limited to univariate analyses. Given numerous clinical variables inform the risk of septic arthritis, multivariable analysis that incorporates all clinically available information is critical to allowing accurate decision-making.

METHODS

We retrospectively identified 455 cases of potential septic arthritis of a native adult knee at a tertiary health system from 2012 to 2017, of which 281 underwent aspiration. We recorded demographics, comorbidities, history, exam, laboratory, and radiographic data. Among aspirated cases, we performed univariate analyses of all variables for association with septic arthritis followed by multivariable logistic regression analysis.

RESULTS

Septic arthritis was confirmed in 61 of 281 patients who underwent aspiration. Independent associations of risk for septic arthritis included synovial fluid WBC ≥ 30,000 (Odds Ratio 90.8, 95% Confidence Interval 26.6-310.1, p < 0.001), bacteria reported on synovial fluid gram stain (OR 21.5, 95% CI 3.9-119.2, p < 0.001), duration of pain >2 days (OR 6.9, 95% CI. 2.3-20.9, p < 0.001), history of septic arthritis at any joint (OR 5.0, 95% CI 1.1-23.4, p = 0.039), clinical effusion (OR 4.8, 95% CI 1.2-20.0, p = 0.030). Independent associations protective against septic arthritis included presence of synovial fluid crystals (OR 0.1, 95% CI 0.1-0.4, p < 0.001). The multivariable model was highly accurate in discriminating between septic and aseptic cases (AUC = 0.942). A web-based tool was created to aid clinical decision-making.

CONCLUSION

When evaluating for septic arthritis of a native adult knee, several independent associations were identified for variables related and unrelated to joint aspiration. The associated multivariable model discriminated very well between patients with and without septic arthritis, outperforming previous univariate assessments. A web-based tool was created that estimates the probability of septic arthritis based on this model. This may aid decision-making in complex clinical scenarios.

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.

Evaluation of automated synovial fluid total cell count and percent polymorphonuclear leukocytes on a Sysmex XN-1000 analyzer for identifying patients at risk of septic arthritis

BACKGROUND

Total cell counts (TC-BF) and percent polymorphonuclear cells (%PMN) of synovial fluid (SF) aspirates provide important cues for the timely diagnosis and management of septic arthritis. To facilitate faster turnaround time, we compared automated to manual TC-BF and differential counts in order to identify reporting cut-offs for automated TC-BF and %PMN that would allow release of automated results concordant with manual counts and differentials.

METHODS

Automated TC-BF and %PMN counts of a non-validated analyzer (Analyzer-B in STAT laboratory) were compared to a validated analyzer (Analyzer-A) and manual TC-BF counts and cytospin differentials. Concordance and %differences of Analyzer-B versus Analyzer-A and manual counts were assessed by linear regression analysis and Bland-Altman comparison.

RESULTS

Overall, automated and manual counts displayed good correlation. A majority of samples demonstrated unacceptable (>20%) differences between automated and manual counts at lower TC-BF (<10,000 cells/μl) and %PMN (<60%).

CONCLUSIONS

Based on good overall correlation and fewer samples with unacceptable (>20%) differences between automated and manual counts, we adopted TC-BF > 10,000 cells/μl and %PMN > 60% as cutoffs for reporting automated counts. These cutoffs minimize differences between automated and manual cell counts and differentials and would allow rapid automated reporting in the vast majority of septic arthritis cases.

Synovial Cell Count Poorly Predicts Septic Arthritis in the Presence of Crystalline Arthropathy

Introduction: A synovial cell count greater than 50,000/mm³ is the threshold most commonly used to diagnose septic arthritis. This lab value may be nonspecific in the setting of crystalline arthropathy. The purpose of this study was to evaluate the accuracy of diagnosing septic arthritis using a synovial cell count cut-off of 50,000/mm³ in the setting of crystalline arthropathy.

Methods: This was a retrospective review of joint aspirations performed between July 1^st, 2013 and June 30^th, 2016. Synovial fluid samples were evaluated for cell count, crystals, Gram stain, and culture. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the synovial markers were calculated.

Results: During the study period, 738 joint aspirations were sent for testing, of which 358 aspirations in 348 patients met inclusion criteria. There were 49 (13.7%) cases of culture-positive septic arthritis, and 47 patients underwent surgical irrigation and debridement. Gout and pseudogout crystals were present in 163 aspirates (45.5%). Three joints (0.8% overall rate) had concomitant crystalline arthropathy and septic arthritis, each of which had a synovial WBC ≥85,000/mm³. Increasing the WBC count cutoff to 85,000/mm³ demonstrated a specificity of 100%, but a PPV of 12.0%.

Conclusions: A cut-off of 85,000/mm³ may be more appropriate to diagnose concomitant septic arthritis and crystalline arthropathy. We recommend medical management and observation in patients with crystal-positive joint aspirations unless the synovial cell count is elevated above 85,000/mm³. Prospective studies using this treatment guideline are needed to evaluate its validity and accuracy.

Performance of a new rapid diagnostic test the lactate/glucose ratio of synovial fluid for the diagnosis of septic arthritis

OBJECTIVE

To evaluate the diagnostic performance of the synovial lactate, glucose and lactate/glucose ratio assay for the diagnosis of septic arthritis.

METHODS

In this monocentric cross-sectional study, synovial fluids were prospectively obtained from patients with acute joint effusion (<30 days) on native joint. Septic arthritis was defined using Newman's criteria. To evaluate diagnostic performance, Receiver Operating Characteristic (ROC) curves with Area under the curve (AUC), Sensitivities (Se), Specificities (Sp), LR+ their 95% confidence intervals were calculated. Synovial fluid cultures with gram staining, crystal analyses, synovial fluid white blood cell counts (WBC), lactate and glucose assays were performed.

RESULTS

A total of 233 synovial fluids were included. 25 patients had septic arthritis and 208 had non-septic arthritis (104 crystal-induced arthritis, 15 RA, 8 SpA, 6 reactive arthritis, and 75 acute arthritis of undifferentiated origin). Synovial lactate/glucose ratio performed higher than the synovial lactate or glucose assay separately (AUC: 0.859 [0.772-0.945]). Best synovial lactate/glucose ratio threshold to differentiate septic arthritis from non-septic arthritis was 5 Se 52% [0.34-0.7], Sp 98.1% [0.95-0.99], LR+ 27.0[9.50-76.00]).

CONCLUSION

The diagnostic performance of synovial lactate/glucose allows septic arthritis to be effectively and very quickly distinguished from other types of arthritis.

Secondary purulent infections of the elbow joint: a retrospective, single-center study

Background

Septic arthritis of the elbow joint is a rare condition. Limited data is available on infections of the elbow joint following trauma or prior surgery on this joint. The aim of this study was to describe the etiology, comorbidities, bacterial spectrum and therapy of secondary purulent elbow infections.

Methods

Patients treated in our hospital were selected through retrospective chart review between 2006 and 2015. We included all patients with an empyema of the elbow after a trauma or surgical intervention on this joint. 30 patients between 26 and 82 years (mean: 52.47) were included.

Results

Seven patients (23.3%) were female, 23 (76.7%) male. 22 patients (73.3%) had a history of trauma, eight (26.7%) had prior elective surgeries on their elbow. Between one and 25 surgeries (mean: 5.77) were necessary for treatment. In nine patients, debridement and synovectomy were sufficient, eight patients (26.7%) received resection of the elbow joint. One patient was treated with a chronic fistula. In 18 patients (60%), cultures of aspiration/intraoperative swabs were positive for Staphylococcus aureus, four of these were methicillin-resistant. Four patients (13.3%) had positive cultures for Staphylococcus epidermidis, in five patients (16.7%) no bacteria could be cultured.

Conclusions

Secondary infections of the elbow joint are a rare disease with potentially severe courses, requiring aggressive surgical treatment and possibly severely impacting elbow function. Staphylococcus aureus was the most common bacteria in secondary infections and should be addressed by empiric antibiotic treatment when no suspicion for other participating organisms is present.

Pilot study of a novel serum mRNA gene panel for diagnosis of acute septic arthritis

BACKGROUND

Septic arthritis is an orthopedic emergency requiring immediate surgical intervention. Current diagnostic standard of care is an invasive joint aspiration. Aspirations provide information about the inflammatory cells in the sample within a few hours, but there is often ambiguity about whether the source is infectious (e.g. bacterial) or non-infectious (e.g. gout). Cultures can take days to result, so decisions about surgery are often made with incomplete data. Novel diagnostics are thus needed. The “Sepsis MetaScore” (SMS) is an 11-mRNA host immune blood signature that can distinguish between infectious and non-infectious acute inflammation. It has been validated in multiple cohorts across heterogeneous clinical settings.

AIM

To study whether the SMS holds diagnostic validity in determining the etiology of acute arthritis.

METHODS

We conducted a blinded, prospective, non-interventional clinical study of the SMS. All patients undergoing work-up for a septic primary joint were enrolled. Patients proceeded through the normal standard-of-care pathway, including joint aspiration and inflammatory labs [white blood cell (WBC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP)]. Venous blood was also drawn into PAX gene RNA-stabilizing tubes and mRNAs were measured using Nano String nCounter™. SMS was calculated blinded to clinical results.

RESULTS

A total of 20 samples were included, of which 11 were infected based on aspiration or intra-operative cultures. The SMS had an area under the ROC curve (AUROC) of 0.87 for separating infectious from non-infectious conditions. For comparison, the AUROCs for ESR = 0.58, CRP = 0.6, and WBC = 0.59. At 100% sensitivity for infection, the specificity of the SMS was 40%, meaning nearly half of non-septic patients could have been ruled out for further intervention.

CONCLUSION

In this pilot study, SMS showed a high level of diagnostic accuracy in predicting septic joints compared to other diagnostic biomarkers. This quick blood test could be an important tool for early, accurate identification of acute septic joints and need for emergent surgery, improving clinical care and healthcare spending.

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.

Performance of automated multiplex polymerase chain reaction (mPCR) using synovial fluid in the diagnosis of native joint septic arthritis in adults

AIMS

This study aimed to assess the performance of an automated multiplex polymerase chain reaction (mPCR) technique for rapid diagnosis of native joint septic arthritis.

PATIENTS AND METHODS

Consecutive patients with suspected septic arthritis undergoing aseptic diagnostic joint aspiration were included. The aspirate was used for analysis by mPCR and conventional microbiological analysis. A joint was classed as septic according to modified Newman criteria. Based on receiver operating characteristic (ROC) analysis, the area under the ROC curve (AUC) values of the mPCR and the synovial fluid culture were compared using the z-test. A total of 72 out of 76 consecutive patients (33 women, 39 men; mean age 64 years (22 to 92)) with suspected septic arthritis were included in this study.

RESULTS

Of 72 patients, 42 (58%) were deemed to have septic joints. The sensitivity of mPCR and synovial fluid culture was 38% and 29%, respectively. No significant differences were found between the AUCs of both techniques (p = 0.138). A strong concordance of 89% (Cohen's kappa: 0.65) was shown. The mPCR failed to detect Staphylococcus aureus (n = 1) and Streptococcus pneumoniae (n = 1; no primer included in the mPCR), whereas the synovial fluid culture missed six microorganisms (positive mPCR: S. aureus (n = 2), Cutibacterium acnes (n = 3), coagulase-negative staphylococci (n = 2)).

CONCLUSION

The automated mPCR showed at least a similar performance to the synovial fluid culture (the current benchmark) in diagnosing septic arthritis, having the great advantage of a shorter turnaround time (within five hours). Cite this article: Bone Joint J 2019;101-B:288-296.

Utility of point-of-care synovial lactate to identify septic arthritis in the emergency department

BACKGROUND

Synovial lactate is a promising biomarker to distinguish septic from aseptic arthritis. If available as a point-of care test, synovial lactate would be rapidly available to aid the emergency provider in clinical decision making. This study assesses the test characteristics of synovial lactate obtained using an EPOC© point-of-care (POC) analyzer to rapidly distinguish septic from aseptic arthritis in the emergency department.

METHODS

We enrolled a convenience sample of patients with possible septic arthritis presenting to the emergency department at a large urban academic center between October 2016 and April 2018. Enrolled patients underwent arthrocentesis based on the clinical judgment of the treating provider. We obtained synovial lactate levels (SLL) from the POC device. Standard laboratory analysis, synovial fluid culture, emergency and hospital course, operative procedures, antibiotics, and discharge diagnosis were abstracted from the electronic medical record.

RESULTS

Thirty-nine patients undergoing forty separate arthrocentesis procedures were enrolled in this study over the two-year period. The sensitivity and specificity of SLL ≥ 5 mmol/L was 0.55 and 0.76 respectively, with +LR 2.3 and -LR 0.6. The sensitivity and specificity of SLL ≥ 10 mmol/L was 0.27 and 0.97 respectively, with +LR 7.9 and -LR 0.8; SLL ≥ 10 mmol/L performed similarly to overall synovial WBC ≥ 50,000/μL by conventional laboratory testing.

CONCLUSION

It is feasible to obtain a synovial lactate level using the EPOC© POC device. In our study, POC SLL performs similarly to other markers used to diagnose septic arthritis. Further study with larger sample sizes is warranted.

Gram Stain is Not Clinically Relevant in Treatment of Pediatric Septic Arthritis

BACKGROUND

The diagnosis of pediatric septic arthritis (SA) can be challenging due to wide variability in the presentation of musculoskeletal infection. Synovial fluid Gram stain is routinely obtained and often used as an initial indicator of the presence or absence of pediatric SA. The purpose of this study was to examine the clinical utility of the Gram stain results from a joint aspiration in the diagnosis and management of pediatric SA.

METHODS

All patients with suspected SA who underwent arthrocentesis and subsequent surgical irrigation and debridement at an urban tertiary care children's hospital between January 2007 and October 2016 were identified. Results of the synovial fluid Gram stain, as well as synovial cell count/differential and serum markers, were evaluated.

RESULTS

A total of 302 patients that underwent incision and drainage for suspected SA were identified. In total, 102 patients (34%) had positive synovial fluid cultures and 47 patients (16%) had a microorganism detected on Gram stain. Gram stain sensitivity and specificity for the detection of SA were 0.40 and 0.97, respectively. This yielded a number needed to misdiagnose of 4.5 (ie, every fifth patient was misdiagnosed by Gram stain). For gram-negative organisms, the sensitivity dropped further to 0.13, with only 2/16 gram-negative organisms identified on Gram stain. Stepwise regression showed that age, serum white blood cell, and absolute neutrophil count were significant independent predictors for having a true positive Gram stain result. Elevated synovial white blood cell count was a significant predictor of having an accurate (culture matching the Gram stain) result.

CONCLUSIONS

The Gram stain result is a poor screening tool for the detection of SA and is particularly ineffective for the detection of gram-negative organisms. The clinical relevance of the Gram stain and cost-effectiveness of this test performed on every joint aspiration sent for culture requires additional evaluation. Patients with gram-negative SA may be at high risk for inadequate coverage with empiric antibiotics due to poor detection of gram-negative organisms on initial Gram stain.

LEVEL OF EVIDENCE

Level III-case-control study.

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.

Hip Synovial Fluid Cell Counts in Children From a Lyme Disease Endemic Area

BACKGROUND

Patients with septic hip arthritis require surgical drainage, but they can be difficult to distinguish from patients with Lyme arthritis. The ability of synovial fluid white blood cell (WBC) counts to help discriminate between septic and Lyme arthritis of the hip has not been investigated.

METHODS

We assembled a retrospective cohort of patients ≤21 years of age with hip monoarticular arthritis and a synovial fluid culture obtained who presented to 1 of 3 emergency departments located in Lyme disease endemic areas. Septic arthritis was defined as a positive synovial fluid culture result or synovial fluid pleocytosis (WBC count ≥50 000 cells per µL) with a positive blood culture result. Lyme arthritis was defined as positive 2-tiered Lyme disease serology results and negative synovial fluid bacterial culture results. All other patients were classified as having other arthritis. We compared median synovial fluid WBC counts by arthritis type.

RESULTS

Of the 238 eligible patients, 26 (11%) had septic arthritis, 32 (13%) had Lyme arthritis, and 180 (76%) had other arthritis. Patients with septic arthritis had a higher median synovial fluid WBC count (126 130 cells per µL; interquartile range 83 303-209 332 cells per µL) than patients with Lyme arthritis (53 955 cells per µL; interquartile range 33 789-73 375 cells per µL). Eighteen patients (56%) with Lyme arthritis had synovial fluid WBC counts ≥50 000 cells per µL. Of the 94 patients who underwent surgical drainage, 13 were later diagnosed with Lyme arthritis.

CONCLUSIONS

In Lyme disease endemic areas, synovial fluid WBC counts cannot always help differentiate septic from Lyme arthritis. Rapid Lyme diagnostics could help avoid unnecessary operative procedures in patients with Lyme arthritis.

An Algorithmic Approach to the Suspected Septic Wrist

An acutely painful, erythematous wrist can be due to a variety of pathologic processes, including crystalline arthropathy, infection, trauma, osteoarthritis, and systemic disease. The broad differential diagnosis of the inflamed wrist and nonspecific clinical findings make accurate diagnosis challenging. There is no published clinical or laboratory criterion that reliably differentiates septic wrist arthritis from a sterile inflammatory arthropathy. For septic joint patients, long-term results are notably poorer in patients with a delay in treatment, therefore establishing evidenced-based guidelines deserves attention.After a comprehensive literature review, we present evidenced-based guidelines and an algorithm for the management of the patient with an acutely inflamed wrist concerning for septic arthritis.For determining a diagnosis, systemic blood laboratory results are extremely variable and unreliable. Despite the attention given to the diagnostic potential of synovial fluid tests, the literature consistently demonstrates that diagnostic certainty cannot always be ascertained at the time of presentation based on aspiration fluid samples. Additionally, the investigative work does not necessarily end at the discovery of crystals since concomitant infection is a rare but well reported entity.Relative to larger joints, the wrist is far less likely to be infected and is easier to drain of debris, and therefore the empiric management of an inflamed wrist joint should reflect these differences. For treatment of the suspected or confirmed septic wrist, prompt initiation with appropriate antibiotics and drainage of joint purulence is critical to rapid recovery. However, the best strategy to clear the joint space of infectious material is controversial. Although the traditional standard of care is open drainage of a septic joint, a growing body of literature supports that for a septic wrist joint, a less invasive approach with serial aspiration can be equally efficacious with reduced morbidity and quicker recovery. If the wrist fails to improve with daily aspirations, then arthroscopy or open washout is needed.For patients with suspected wrist joint infection or crystalline arthropathy with probable concomitant infection, a reasonable approach is admission for systemic antibiotics and daily arthrocentesis. If the wrist fails to improve or worsens, then surgical treatment may be pursued. This treatment strategy could potentially avoid the morbidity of surgery while ensuring that no septic wrist goes untreated.

Optimization of Cellular analysis of Synovial Fluids by optical microscopy and automated count using the Sysmex XN Body Fluid Mode

BACKGROUND

This study was planned to assess the impact of pre-treating synovial fluid (SF) samples with hyaluronidase (HY), defining the best procedure for optical microscopy (OM) analysis and evaluating the performance of Sysmex XN-9000 Body Fluid module (XN-BF).

METHODS

The cell count by OM was carried out both with and without HY pre-treatment, and using 3 different types of staining reagents. The evaluation of XN-BF included data comparison with OM (100 SFs), carryover, Limit of Blank (LoB), Limit of Detection (LoD), Limit of Quantitation (LoQ) and linearity.

RESULTS

Unlike cell count in Burker's chamber and staining with Stromatol, pre-treatment with HY and staining with Methylene Blue and Turk's promoted cell clustering. The SF samples pre-treated with HY displayed excellent morphological quality, contrary to samples without HY pre-treatment. Excellent correlation was found between total cells counting with both OM and XN-BF. Satisfactory agreement was also observed between polymorphonuclear neutrophils compared to XN-BF parameter, whereas mononuclear cell count on XN-BF had suboptimal agreement with OM. The carryover was negligible. The LoB, LoD, LoQ and linearity were excellent.

CONCLUSION

XN-BF displays excellent performance, which makes it a reliable and practical alternative to OM for SF samples analysis in clinical laboratories.

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.].

Rapid exclusion of bacterial arthritis using a glucometer

Bacterial arthritis is a medical emergency. However, prompt diagnosis and differentiation from non-infectious diseases are challenging. As bacterial metabolism leads to glucose reduction, measurement of synovial fluid glucose seems to be a promising diagnostic approach. The purpose of this study was to determine whether synovial fluid glucose levels could be accurately measured by using a glucometer and to evaluate its diagnostic accuracy in diagnosing bacterial arthritis compared to currently available markers. In a prospective diagnostic study, 102 consecutive patients with atraumatic joint effusion were included. Synovial fluid glucose concentrations were determined using both glucometer and automated analyzer respectively. Synovial fluid culture, crystal analysis, and synovial cell analysis were performed. Blood samples were taken for blood cultures, analyses of serum infection markers, and serum glucose. There was a high correlation between synovial fluid glucose measured by the glucometer and the automated analyzer (r ² = 0.92). According to the receiver operating characteristic curve, a threshold of 1.4 mmol/l had a sensitivity of 100 % (95 % CI 78.2-100 %), a specificity of 92.0 % (95 % CI 84.1-96.7 %), a positive predictive value of 68.2 % (95 % CI 45.1-86.1 %), and a negative predictive value of 100 % (95 % CI 95.5-100 %). These results suggest that synovial fluid glucose concentrations could be reliably measured using a glucometer. Due to its simplicity, this test has the potential to be an adjunct in the diagnostic cascade of bacterial arthritis.

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

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

Pediatric Rheumatology for the Primary Care Clinicians-Recognizing Patterns of Disease

This review presents a diagnostic approach to musculoskeletal and rheumatic diseases in children for primary care clinicians. The focus is on juvenile idiopathic arthritis (JIA) as the major arthritis disease in children. It is necessary to know the personalities of these JIA categories. It is also crucial to be able to recognize the common infectious, orthopedic and mechanical, malignant, genetic, other rheumatic diseases, and other miscellaneous syndromes that can mimic JIA. To do so requires recognition of clinical patterns using a thorough musculoskeletal and rheumatic history and repeated complete physical exams with emphasis on the musculoskeletal exam. It also requires targeted and limited laboratory testing with careful follow-up over time.

Preoperative antibiotics for septic arthritis in children: delay in diagnosis

PURPOSE

To review the records of 50 children who underwent open joint washout for septic arthritis with (n=25) or without (n=25) preoperative antibiotics.

METHODS

Records of 50 children who underwent open joint washout for presumed septic arthritis with (n=25) or without (n=25) preoperative antibiotics were reviewed. 17 boys and 8 girls aged 3 weeks to 16 years (median, 1.5 years) who were prescribed preoperative antibiotics before joint washout were compared with 12 boys and 13 girls aged one month to 14 years (median, 2 years) who were not. Following arthrotomy and washout, all patients were commenced on high-dose intravenous antibiotics. Patients were followed up for 6 to 18 months until asymptomatic.

RESULTS

Patients who were referred from places other than our emergency department were twice as likely to have been prescribed preoperative antibiotics (p=0.0032). Patients prescribed preoperative antibiotics had a longer median (range) time from symptom onset to joint washout (8 [2-23] vs. 4 [1-29] days, p=0.05) and a higher mean erythrocyte sedimentation rate (93.1 vs. 54.3 mm/h, p=0.023) at presentation. Nonetheless, the 2 groups were comparable for weight bearing status, fever, and positive culture, as well as the mean (range) duration of antibiotic treatment (4.9 [4-7] vs. 4.7 [1-8] weeks, p=0.586).

CONCLUSION

Preoperative antibiotics should be avoided in the management of septic arthritis in children. Their prescription delays diagnosis and definitive surgery, and leads to additional washouts and complications. A high index of suspicion and expedite referral to a specialist paediatric orthopaedic unit is needed if septic arthritis is suspected.

Management of pediatric patients with synovial fluid white blood-cell counts of 25,000 to 75,000 cells/mm³ after aspiration of the hip

BACKGROUND

In this study, we sought to elucidate the presentation, clinical course, treatments pursued, final diagnosis, and risk factors for septic arthritis in a series of children with hip pain and intermediate synovial fluid values (white blood-cell [WBC] counts of 25,000 to 75,000 cells/mm(3) [25 to 75 × 10(9) cells/L]).

METHODS

We reviewed the records of pediatric patients who underwent hip aspiration between 2005 and 2012 at a tertiary-care pediatric hospital. Demographic data, laboratory values, final diagnosis, and treatment details were recorded for the subpopulation of patients with an aspirate WBC count of 25,000 to 75,000 cells/mm(3) (25 to 75 × 10(9) cells/L). Univariate and multivariable logistic regression analysis was used to assess risk factors for septic arthritis of the hip across final diagnostic groups and subgroups with WBC values of <50,000 and ≥50,000 cells/mm(3) (<50 and ≥50 × 10(9) cells/L).

RESULTS

Forty-six children (twenty-seven males and nineteen females) with a mean age of 7.6 years met the inclusion criteria. The final diagnoses were septic arthritis of the hip (n = 15; 33%), Lyme arthritis (n = 13; 28%), transient synovitis (n = 8; 17%), and other findings (n = 10; 22%). Subjects with a synovial fluid WBC count of ≥50,000 cells/mm(3) (≥50 × 10(9) cells/L) were more likely to be diagnosed with septic arthritis of the hip (odds ratio, 4.4; 95% confidence interval, 1.1 to 16.9; p = 0.03). While septic arthritis of the hip was the most common diagnosis (48%) in patients with WBC values of ≥50,000 cells/mm(3) (≥50 × 10(9) cells/L), it also represented 17% of cases with WBC values of <50,000 cells/mm(3) (<50 × 10(9) cells/L).

CONCLUSIONS

Septic arthritis of the hip is the most common ultimate diagnosis in children with synovial fluid WBC values of 25,000 to 75,000 cells/mm(3) (25 to 75 × 10(9) cells/L) following hip aspiration, and it should be high on the differential diagnosis, even in cases with synovial fluid WBC values of <50,000 cells/mm(3) (<50 × 10(9) cells/L).

Acute hand infections

The continued emergence of antibiotic-resistant bacteria and the development of only a few new classes of antibiotics over the past 50 years have made the treatment of acute hand infections problematic. Prompt diagnosis and treatment are important, because hand stiffness, contractures, and even amputation can result from missed diagnoses or delayed treatment. The most common site of hand infections is subcutaneous tissue and the most common mechanism is trauma. An immunocompromised state, intravenous drug abuse, diabetes mellitus, and steroid use all predispose to infections.