Mark B. Coventry Award: synovial C-reactive protein: a prospective evaluation of a molecular marker for periprosthetic knee joint infection

Tryptophanyl tRNA synthetase is an alternative synovial biomarker for diagnosis of septic arthritis in knee joint

BACKGROUND

To evaluate the diagnostic characteristics of tryptophanyl tRNA synthetase (WRS) for the diagnosis of septic arthritis of the knee joint and to determine whether it is a reliable and sensitive synovial biomarker for discriminating septic arthritis from other types of arthritis.

METHODS

Patients joint effusions for which septic arthritis was suspected were prospectively recruited between January 2019 and September 2020. A total of 9 patients had septic arthritis, 6 had acute gout attack, 1 had an acute flare of chronic rheumatic arthritis, and 46 had pseudogout or reactive arthropathy. Traditional inflammatory markers were measured, and their diagnostic abilities were compared. Neutrophil count, C-reactive protein (CRP) level, WRS, and human neutrophil α-defensin levels were assessed in the synovial fluids. Demographic parameters and biomarkers with a P < 0.05 in differentiating septic from nonseptic arthritis were included in a multivariable model. A multivariable logistic regression with a stepwise selection was performed to build the final combined model. Receiver operating characteristic curves were used to establish optimal thresholds for the diagnosis of septic arthritis of the knee joint, and the area under the curve was calculated to determine the overall accuracy of these tests compared with patients with nonseptic inflammatory arthritis.

RESULTS

Patients with septic arthritis were more likely to display higher serum WBC and CRP levels, synovial neutrophil counts, and levels of two synovial biomarkers, including WRS and α-defensin. WRS showed the highest specificity (87.5%) and sensitivity (83.3%) with α-defensin among the three synovial biomarkers.

CONCLUSIONS

Synovial fluid WRS is a relevant biomarker in discriminating septic arthritis from other inflammatory arthritis and should be tested in an independent cohort.

LEVEL OF EVIDENCE

prospective observational study, III.

Serum and Synovial Markers in the Diagnosis of Periprosthetic Joint Infection of the Hip, Knee, and Shoulder: An Algorithmic Approach

➤ No single test has demonstrated absolute accuracy for the diagnosis of periprosthetic joint infection (PJI).➤ Physicians rely on a combination of serological tests, synovial markers, and clinical findings plus clinical judgment to help to guide preoperative decision-making.➤ Several organizations have proposed criteria for the diagnosis of hip or knee PJI on which we now rely.➤ Given that shoulder arthroplasty has only recently become popular, it is possible that a shoulder-specific definition of PJI will be introduced in the coming years.➤ Although a number of serum and synovial markers have demonstrated high accuracy for the diagnosis of PJI of the hip and knee, further research is needed in order to identify markers that may be more suitable for the diagnosis of shoulder PJI and for the potential development and identification of specific serological tests as screening tools for PJI.

Diagnostics in Late Periprosthetic Infections-Challenges and Solutions

The rising number of arthroplasties is combined with a rising number of periprosthetic joint infections, which leads to life-concerning consequences for the patients, including extended antibiotic treatment, further surgery and increased mortality. The heterogeneity of the symptoms and inflammatory response of the patients due to, e.g., age and comorbidities and the absence of a single diagnostic test with 100% accuracy make it very challenging to choose the right parameters to confirm or deny a periprosthetic joint infection and to establish a standardized definition. In recent years, additional diagnostic possibilities have emerged primarily through the increasing availability of new diagnostic methods, such as genetic techniques. The aim of the review is to provide an overview of the current state of knowledge about the various tests, including the latest developments. The combination of different tests increases the accuracy of the diagnosis. Each physician or clinical department must select the tests from the available methods that can be best implemented for them in organizational and technical terms. Serological parameters and the cultivation of the samples from aspiration or biopsy should be combined with additional synovial tests to create an accurate figure for the failure of the prosthesis, while imaging procedures are used to obtain additional information for the planned therapeutic procedure.

Acidity Is an Excellent Marker of Infection in Hip and Knee Arthroplasty

BACKGROUND

The diagnosis of joint replacement infection is a difficult clinical challenge that often occurs when the implant cannot be salvaged. We hypothesize that the pH value of synovial fluid could be an important indicator of the inflammatory status of the joint. However, in the literature, there is a lack of data on the pH changes in hip and knee joint replacements and their relation to infection and implant failure. In this study, we aimed to measure the pH levels of synovial fluid in patients with hip and knee joint replacements. We also investigated the potential of pH measurement as a diagnostic tool for joint replacement infection. In this study, we recorded the pH values to be 7.55 and 7.46 in patients where Pseudomonas aeruginosa was identified as the cause of the prosthetic joint infection. We attribute this to the different environments created by this specific bacterium. In other cases where the pH was higher, chronic mitigated infections were diagnosed, caused by strains of Staphylococcus aureus, Streptococcus agalactiase, and coagulase negative staphylococcus.

MATERIALS AND METHODS

In our cohort of 155 patients with implanted hip (THA; n = 85) or knee (TKA; n = 70) joint replacements, we conducted a prospective study with a pH measurement. Out of the whole cohort, 44 patients had confirmed joint replacement infection (28.4%) (44/155). In 111 patients, infection was ruled out (71.6%) (111/155). Joint replacement infection was classified according to the criteria of the Musculoskeletal Infection Society (MSIS) from 2018. Based on the measured values, we determined the cut-off level for the probability of ongoing inflammation. We also determined the sensitivity and specificity of the measurement.

RESULTS

The group of patients with infection (n = 44) had a significantly lower synovial fluid pH (pH = 6.98 ± 0.48) than the group of patients with no infection (n = 111, pH = 7.82 ± 0.29, p < 0.001). The corresponding median pH values were 7.08 for the patients with infection and 7.83 for the patients with no infection. When we determined the cut-off level of pH 7.4, the sensitivity level of infected replacements was 88.6%, and the specificity level of the measurement was 95.5%. The predictive value of a positive test was 88.6%, and the predictive value of a negative test was 95.5%.

CONCLUSIONS

Our results confirm that it is appropriate to include a pH measurement in the diagnostic spectrum of hip and knee replacements. This diagnostic approach has the potential to provide continuous in vivo feedback, facilitated by specialized biosensors. The advantage of this method is the future incorporation of a pH-detecting sensor into intelligent knee and hip replacements that will assess pH levels over time. By integrating these biosensors into intelligent implants, the early detection of joint replacement infections could be achieved, enhancing proactive intervention strategies.

Synovial Fluid C-reactive Protein Clinical Decision Limit and Diagnostic Accuracy for Periprosthetic Joint Infection

Introduction C-reactive protein (CRP) has long served as a prototypical biomarker for periprosthetic joint infection (PJI). Recently, synovial fluid (SF)-CRP has garnered interest as a diagnostic tool, with several studies demonstrating its diagnostic superiority over serum CRP for the diagnosis of PJI. Although previous studies have identified diagnostic thresholds for SF-CRP, they have been limited in scope and employed various CRP assays without formal validation for PJI diagnosis. This study aimed to conduct a formal single clinical laboratory validation to determine the optimal clinical decision limit of SF-CRP for the diagnosis of PJI. Methods A retrospective analysis of prospectively collected data was performed using receiver operating characteristic (ROC) and area under the curve (AUC) analyses. Synovial fluid samples from hip and knee arthroplasties, received from over 2,600 institutions, underwent clinical testing for PJI at a single clinical laboratory (CD Laboratories, Zimmer Biomet, Towson, MD) between 2017 and 2022. Samples were assayed for SF-CRP, alpha-defensin, white blood cell count, neutrophil percentage, and microbiological culture. After applying selection criteria, the samples were classified with the 2018 ICM PJI scoring system as "infected," "not infected," or "inconclusive." Data were divided into training and validation sets. The Youden Index was employed to optimize the clinical decision limit. Results A total of 96,061 samples formed the training (n = 67,242) and validation (n = 28,819) datasets. Analysis of the biomarker median values, culture positivity, anatomic distribution, and days from aspiration to testing revealed nearly identical specimen characteristics in both the training set and validation set. SF-CRP demonstrated an AUC of 0.929 (95% confidence interval (CI): 0.926-0.932) in the training set, with an optimal SF-CRP clinical decision limit for PJI diagnosis of 4.45 mg/L. Applying this cutoff to the validation dataset yielded a sensitivity of 86.1% (95% CI: 85.0-87.1%) and specificity of 87.1% (95% CI: 86.7-87.5%). No statistically significant difference in diagnostic performance was observed between the validation and training sets. Conclusion This study represents the largest single clinical laboratory evaluation of an SF-CRP assay for PJI diagnosis. The optimal CRP cutoff (4.45 mg/L) for PJI, which yielded a sensitivity of 86.1% and a specificity of 87.1%, is specific to the assay methodology and laboratory performing the assay. We propose that an SF-CRP test with a laboratory-validated optimal clinical decision limit for PJI may be preferable, in a clinical diagnostic setting, to serum CRP tests that do not have laboratory-validated clinical decision limits for PJI.

Serum procalcitonin has no significance in the diagnosis of periprosthesis joint infection before total hip and knee replacement

Background

Currently, there is no "gold standard" for early diagnosing PJI. The diagnosis of periprosthetic joint infection (PJI) is a challenging problem in the clinic. As we know, many serum markers have been used in the early diagnosis of PJI. The aim of this study was to validate the value of PCT in the diagnosis of PJI.

Methods

A retrospective review of 77 patients with revision arthroplasties from January 2013 to July 2020 was conducted. PJI was defined using the modified Musculoskeletal Infection Society (MSIS) criteria combined with follow-up results. Besides medical history, clinical and laboratory data was gathered. Preoperative blood was taken for serum PCT and other biomarkers measurement. Receiver operating characteristic (ROC) curves were generated to evaluate the biomarkers' diagnostic performance and optimal cut-off value.

Results

Forty-one patients were identified as the PJI group (27 hips and 14 knees), while thirty-six patients were identified as the aseptic loosening (AL) group (33 hips and 3 knees). The AUCs for C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), Platelets (PLT), Fibrinogen (FIB), and Procalcitonin (PCT) were 0.845 (95% CI 0.755-0.936, p < 0.001), 0.817 (95% CI 0.718-0.916, p < 0.001), 0.728 (95% CI 0.613-0.843, p < 0.001), 0.810 (95% CI 0.710-0.910, p < 0.001) and 0.504 (95% CI 0.373-0.635, p = 0.950), respectively. Higher Area under the Curve (AUC) values were obtained for the combinations of PCT and CRP (AUC = 0.870) (95% CI, 0.774-0.936), PCT and ESR (AUC = 0.817) (95% CI, 0.712-0.896), PCT and PLT (AUC = 0.731) (95% CI, 0.617-0.825), PCT and FIB (AUC = 0.815) (95% CI, 0.710-0.894). The serum PCT indicated a sensitivity of 19.51% and a specificity of 83.33% for diagnosing PJI. When the optimal cut-off value for PCT was set as 0.05 ng/ml, its positive and negative likelihood ratios were 57.1% and 47.6%, respectively.

Conclusion

In conclusion, serum PCT appeared to be no reliable biomarker in differentiating PJI from aseptic loosening before revision arthroplasties. However, PCT combined with other biomarkers further increases the diagnostic accuracy.

An artificial intelligence framework for the diagnosis of prosthetic joint infection based on 99mTc-MDP dynamic bone scintigraphy

OBJECTIVES

Dynamic bone scintigraphy (DBS) is the first widely reliable and simple imaging modality in nuclear medicine that can be used to diagnose prosthetic joint infection (PJI). We aimed to apply artificial intelligence to diagnose PJI in patients after total hip or knee arthroplasty (THA or TKA) based on 99mTc-methylene diphosphonate (99mTc-MDP) DBS.

METHODS

A total of 449 patients (255 THAs and 194 TKAs) with a final diagnosis were retrospectively enrolled and analyzed. The dataset was divided into a training and validation set and an independent test set. A customized framework composed of two data preprocessing algorithms and a diagnosis model (dynamic bone scintigraphy effective neural network, DBS-eNet) was compared with mainstream modified classification models and experienced nuclear medicine specialists on corresponding datasets.

RESULTS

In the fivefold cross-validation test, diagnostic accuracies of 86.48% for prosthetic knee infection (PKI) and 86.33% for prosthetic hip infection (PHI) were obtained using the proposed framework. On the independent test set, the diagnostic accuracies and AUC values were 87.74% and 0.957 for PKI and 86.36% and 0.906 for PHI, respectively. The customized framework demonstrated better overall diagnostic performance compared to other classification models and showed superiority in diagnosing PKI and consistency in diagnosing PHI compared to specialists.

CONCLUSION

The customized framework can be used to effectively and accurately diagnose PJI based on 99mTc-MDP DBS. The excellent diagnostic performance of this method indicates its potential clinical practical value in the future.

KEY POINTS

• The proposed framework in the current study achieved high diagnostic performance for prosthetic knee infection (PKI) and prosthetic hip infection (PHI) with AUC values of 0.957 and 0.906, respectively. • The customized framework demonstrated better overall diagnostic performance compared to other classification models. • Compared to experienced nuclear medicine physicians, the customized framework showed superiority in diagnosing PKI and consistency in diagnosing PHI.

Joint aspiration for diagnosis of chronic periprosthetic joint infection: when, how, and what tests?

Diagnosing chronic periprosthetic joint infection (PJI) requires clinical suspicion in combination with both serological and synovial fluid tests, the results of which are generally applied to validated scoring systems or consensus definitions for PJI. As no single "gold standard" test exists, the diagnosis becomes challenging, especially in the setting of negative cultures or equivocal test results. This review aims to address the workup of chronic PJI and considerations for clinical evaluation to guide treatment. Following aspiration of the joint in question, a multitude of tests has been developed in an attempt to assist with diagnosis, including cell synovial white blood cell count, gram stain, cultures, leukocyte esterase, alpha-defensin, synovial C-reactive protein, multiplex polymerase chain reaction, next-generation sequencing, and interleukins. Each test has advantages and disadvantages and should be used in conjunction with the overall clinical picture to guide further clinical evaluation and treatment in this complex patient population.

Diagnosis of Periprosthetic Joint Infection: The Utility of Biomarkers in 2023

Periprosthetic joint infection (PJI) is a rare yet devastating complication following total joint arthroplasty (TJA). Early and accurate diagnosis of PJI is paramount in order to maximize the chances of successful treatment. However, we are yet to identify a single "gold standard" test for the diagnosis of PJI. As a result, the diagnosis of PJI is often challenging. Currently, the 2018 ICM definition of PJI is the only validated diagnostic criteria available. This article will review the importance of serum and synovial biomarkers in the diagnosis of PJI. In addition, it will provide a brief overview of the emerging modalities for the identification of infections in this setting.

Profiling the Immune Response to Periprosthetic Joint Infection and Non-Infectious Arthroplasty Failure

Arthroplasty failure is a major complication of joint replacement surgery. It can be caused by periprosthetic joint infection (PJI) or non-infectious etiologies, and often requires surgical intervention and (in select scenarios) resection and reimplantation of implanted devices. Fast and accurate diagnosis of PJI and non-infectious arthroplasty failure (NIAF) is critical to direct medical and surgical treatment; differentiation of PJI from NIAF may, however, be unclear in some cases. Traditional culture, nucleic acid amplification tests, metagenomic, and metatranscriptomic techniques for microbial detection have had success in differentiating the two entities, although microbiologically negative apparent PJI remains a challenge. Single host biomarkers or, alternatively, more advanced immune response profiling-based approaches may be applied to differentiate PJI from NIAF, overcoming limitations of microbial-based detection methods and possibly, especially with newer approaches, augmenting them. In this review, current approaches to arthroplasty failure diagnosis are briefly overviewed, followed by a review of host-based approaches for differentiation of PJI from NIAF, including exciting futuristic combinational multi-omics methodologies that may both detect pathogens and assess biological responses, illuminating causes of arthroplasty failure.

Synovial C-Reactive Protein is a Useful Adjunct for Diagnosis of Periprosthetic Joint Infection

BACKGROUND

The diagnostic utility of synovial C-reactive protein (CRP) has been debated for a while. Existing studies are limited by small sample sizes and using outdated criteria for periprosthetic joint infection (PJI). Furthermore, the relationship between synovial and serum CRP has rarely been investigated in the setting of PJI. This study aimed to evaluate the diagnostic utility of synovial CRP and to assess its relationship with serum CRP and other common biomarkers.

METHODS

We reviewed 621 patients who underwent evaluation for PJI prior to revision arthroplasty from 2014 to 2021. Biomarkers, including serum CRP and erythrocyte sedimentation rate, synovial CRP, polymorphonuclear leukocyte percentage, white blood cell count, and alpha-defensin, were evaluated using the 2018 International Consensus Meeting criteria.

RESULTS

In total, 194 patients had a PJI; 394 were considered aseptic failures and 33 were inconclusive. Synovial CRP showed an area under the curve (AUC) of 0.951 (95% CI, 0.932-0.970) with 74.2% sensitivity and 98.0% specificity, whereas, serum CRP had an AUC of 0.926 (95% CI, 0.903-0.949) with 83.5% sensitivity and 88.3% specificity. There was a good correlation between synovial and serum CRP (R = 0.703; 95% CI, 0.604-0.785). The combination of serum and synovial CRP yielded a significantly higher AUC than that obtained when using serum CRP alone (AUC 0.964 versus 0.926, P = .016).

CONCLUSION

Synovial CRP demonstrated excellent accuracy when used to determine the presence of PJI. There was a good correlation between serum and synovial CRP levels in revision arthroplasty patients and the combined use of serum and synovial CRP proved to be more accurate than the serum test alone. These findings support the use of synovial CRP as an adjunct in the workup of PJI.

Reliable Diagnostic Tests and Thresholds for Preoperative Diagnosis of Non-Inflammatory Arthritis Periprosthetic Joint Infection: A Meta-analysis and Systematic Review

Objective

The current diagnostic criteria for periprosthetic joint infection (PJI) are diverse and controversial, leading to delayed diagnosis. This study aimed to evaluate and unify their diagnostic accuracy and the threshold selection of serum and synovial routine tests for PJI at an early stage.

Methods

We searched the MEDLINE and Embase databases for retrospective or prospective studies which reported preoperative‐available assays (serum, synovial, or culture tests) for the diagnosis of chronic PJI among inflammatory arthritis (IA) or non‐IA populations from January 1, 2000 to June 30, 2022. Threshold effective analysis was performed on synovial polymorphonuclear neutrophils (PMN%), synovial white blood cell (WBC), serum C‐reactive protein (CRP), and erythrocyte sedimentation rate (ESR) to find the relevant cut‐offs.

Results

Two hundred and sixteen studies and information from 45,316 individuals were included in the final analysis. Synovial laboratory‐based α‐defensin and calprotectin had the best comprehensive sensitivity (0.91 [0.86–0.94], 0.95 [0.88–0.98]) and specificity (0.96 [0.94‐0.97], 0.95 [0.89–0.98]) values. According to the threshold effect analysis, the recommended cut‐offs are 70% (sensitivity 0.89 [0.85–0.92], specificity 0.90 [0.87–0.93]), 4100/μL (sensitivity 0.90 [0.87–0.93], specificity 0.97 [0.93–0.98]), 13.5 mg/L (sensitivity 0.84 [0.78–0.89], specificity 0.83 [0.73–0.89]), and 30 mm/h (sensitivity 0.79 [0.74–0.83], specificity 0.78 [0.72–0.83]) for synovial PMN%, synovial WBC, serum CRP, and ESR, respectively, and tests seem to be more reliable among non‐IA patients.

Conclusions

The laboratory‐based synovial α‐defensin and synovial calprotectin are the two best independent preoperative diagnostic tests for PJI. A cut off of 70% for synovial PMN% and tighter cut‐offs for synovial WBC and serum CRP could have a better diagnostic accuracy for non‐IA patients with chronic PJI.

Diagnosing Periprosthetic Joint Infection: a Scoping Review

PURPOSE OF REVIEW

The goal of this review is to provide an up to date understanding of the utility and limitations of the current tests utilized in the diagnosis of periprosthetic joint infection (PJI) in total knee and hip arthroplasty.

RECENT FINDINGS

Despite the growth in literature surrounding PJI diagnosis, there remains challenges in establishing a diagnosis of PJI. A combination of clinical, serum, and synovial tests and microbiologic and histologic examinations can yield a diagnosis in the majority of cases. Novel molecular and imaging studies may be beneficial for indeterminant cases. A number of emerging diagnostic tests have been proposed and may be incorporated into diagnostic algorithms in the future. Recently proposed stepwise diagnostic algorithms have shown high sensitivity and specificity. The diagnosis of PJI remains challenging due to a lack of tests that can definitively rule out infection. Diagnosis and investigations should occur in a stepwise fashion. There has been a plethora of new diagnostic tests introduced in attempts to improve the accuracy of diagnostic algorithms. The definition and algorithms for the diagnoses of PJI will continue to evolve as new techniques and tests are introduced.

Synovial fluid pH sensor for early detection of prosthetic hip infections

We describe an implantable sensor developed to measure synovial fluid pH for noninvasive early detection and monitoring of hip infections using standard-of-care plain radiography. The sensor was made of a pH responsive polyacrylic acid-based hydrogel, which expands at high pH and contracts at low pH. A radiodense tantalum bead and a tungsten wire were embedded in the two ends of the hydrogel in order to monitor the change in length of the hydrogel sensor in response to pH via plain radiography. The effective pKa of the hydrogel-based pH sensor was 5.6 with a sensitivity of 3 mm/pH unit between pH 4 and 8. The sensor showed a linear response and reversibility in the physiologically relevant pH range of pH 6.5 and 7.5 in both buffer and bovine synovial fluid solutions with a 30-minute time constant. The sensor was attached to an explanted prosthetic hip and the pH response determined from the X-ray images by measuring the length between the tantalum bead and the radiopaque wire. Therefore, the developed sensor would enable noninvasive detection and studying of implant hip infection using plain radiography.

Combined serum and synovial C-reactive protein tests: a valuable adjunct to the diagnosis of chronic prosthetic joint infection

Background

Diagnosis of periprosthetic joint infection (PJI), especially chronic PJI, is very confusing and challenging. The value of C-reactive protein (CRP) in infectious diseases has been recognized, but the diagnostic value of CRP in chronic PJI is unknown. Our aim was to investigate the diagnostic value of synovial CRP in chronic PJI and to explore the role of combined serum and synovial CRP in distinguishing chronic PJI from aseptic failure after knee and hip arthroplasties.

Methods

We prospectively enrolled patients scheduled to have a revision surgery for chronic PJI or aseptic loosening from January 2019 to December 2020, in which synovial CRP was additionally measured along with routine preoperative diagnostic serum ((ESR, CRP) and synovial (PMN%) biomarkers. The receiver operating characteristic (ROC) curves and area under the curve (AUC) were analyzed for each biomarker to determine diagnostic efficacy.

Results

There were no statistically significant differences between the infection (n = 39) and aseptic (n = 58) groups, including 61 hips and 36 knees. The synovial CRP levels were significantly higher in the infection group than in the aseptic group (median: 9.93 mg/l vs 3.58 mg/l; p < .001). The optimal cut-off value for detecting chronic PJI of Synovial fluid (SF) CRP was of 7.26 mg/l with a sensitivity of 84.62%, a specificity of 93.10%. The combined model I (Serum CRP > 10.2 mg/l OR SF CRP > 7.26 mg/l) had a negative predictive value (NPV) of 96.67%, and a sensitivity of 97.44%. The combined model II (Serum CRP > 10.2 mg/l AND Synovial CRP > 7.26 mg/l) led to a specificity of 1, and a positive predictive value (PPV) of 1.

Conclusions

The present study demonstrated that the combination of serum and synovial CRP can be used as an adjunct to the diagnosis of chronic PJI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04545-6.

Serum and Synovial Biomarkers for the Diagnosis of Implant-Associated Infection After Orthopedic Surgery

Implant-associated infection is one of the most devastating complications following orthopedic surgery. Early identification is crucial for treatment. Currently, however, a reliable diagnostic tool is lacking, partly due to disparate bacteria colonies (virulent vs non-virulent), difficulty in distinguishing infection from inflammatory disease, and highly diverse diagnostic thresholds and testing methods. Given the importance of biomarkers in the initial screening for the infection, an extensive effort has been made to develop serum and synovial biomarkers. In this review, the authors summarize the results from the most relevant studies to provide comprehensive information on biomarkers for the diagnosis of implant-associated infection. [Orthopedics. 2021;44(2):e158-e166.].

Value of the synovial C-reactive protein test in the diagnosis of total hip and knee periprosthetic joint infections: A case-control study

INTRODUCTION

The diagnosis of periprosthetic joint infection (PJI) can be challenging and rests on several principles. The use of diagnostic biomarkers, such as the synovial C-Reactive Protein (CRP), seems promising. The purpose of this study was to determine whether synovial CRP was a more discriminating test than serum CRP for the diagnosis of hip and knee PJI.

MATERIALS AND METHODS

In total, 194 patients were included in this single center prospective study: 42 primary arthroplasties (control group [CG]), 111 revisions for aseptic prosthesis (aseptic revision group [ARG]), and 41 revisions for septic prosthesis (septic revision group [SRG]) based on the Musculoskeletal Infection Society (MSIS) criteria.

RESULTS

The serum and synovial CRP levels were significantly higher in the SRG than the other two groups (SRG serum CRP=75.6mg/L vs. ARG serum CRP=6mg/L and CG serum CRP=2.7mg/L, p<0.001; SRG synovial CRP=31.5mg/L vs. CG synovial CRP=2.6mg/L and ARG synovial CRP=1.7mg/L, p<0.001). The positive likelihood ratios (LR+) were very similar for both the synovial CRP cut-off value of 4.4mg/L (LR+=7.04; sensitivity [Se] 82.5%, specificity [Sp] 88.3%) and the serum CRP cut-off value of 9mg/L (LR+=6.3; Se 87.5%, Sp 86.1%).

CONCLUSION

This study showed that synovial CRP testing was not more discriminating than serum CRP in the diagnosis of hip and knee PJI. A serum CRP level greater than 9mg/L was a sign of PJI.

LEVEL OF EVIDENCE

III; case-control study.

Concomitant Hip and Knee Periprosthetic Joint Infection in Periprosthetic Fracture: Diagnostic Utility of Serum and Synovial Fluid Markers

BACKGROUND

Diagnosing periprosthetic joint infection (PJI) in patients with a periprosthetic fracture can be challenging due to concerns regarding the reliability of commonly used serum and synovial fluid markers. This study aimed at determining the diagnostic performance of serum and synovial fluid markers for diagnosing PJI in patients with a periprosthetic fracture of a total joint arthroplasty.

METHODS

A total of 144 consecutive patients were included: (1) 41 patients with concomitant PJI and periprosthetic fracture and (2) 103 patients with periprosthetic fracture alone. Serum markers erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), and synovial markers white blood cell (WBC) count and polymorphonuclear percentage were assessed.

RESULTS

ESR demonstrated 87% sensitivity and 48% specificity at the Musculoskeletal Infection Society threshold, area under the curve (AUC) of 0.74, and optimal threshold of 45.5 mm/h (76% sensitivity, 68% specificity). CRP showed 94% sensitivity and 40% specificity, AUC of 0.68 with optimal threshold of 16.7 mg/L (84% sensitivity, 51% specificity). Synovial WBC count demonstrated 87% sensitivity and 78% specificity, AUC of 0.90 with optimal threshold of 4552 cells/μL (86% sensitivity, 85% specificity). Polymorphonuclear percentage showed 79% sensitivity and 63% specificity, AUC of 0.70 with optimal threshold of 79.5% (74% sensitivity, 63% specificity). The AUC of all combined markers was 0.90 with 84% sensitivity and 79% specificity.

CONCLUSION

The diagnostic utility of the serum and synovial markers for diagnosing PJI was lower in the setting of concomitant periprosthetic fracture compared to PJI alone. Using the Musculoskeletal Infection Society thresholds, ESR, CRP, and WBC count showed high sensitivity, yet low specificity, thus higher thresholds and utilizing all serum and synovial markers in combination should be considered.

Synovial Fluid Aspirates Diluted with Saline or Blood Reduce the Sensitivity of Traditional and Contemporary Synovial Fluid Biomarkers

BACKGROUND

Recent criteria-based diagnostic tools to diagnose periprosthetic infection (PJI), such as the International Consensus Meeting (ICM) definition of PJI, are heavily reliant on synovial fluid laboratory results. Despite the importance of synovial fluid in PJI diagnosis, the effect of the quality of synovial fluid aspirate on testing results has not been studied. Our laboratory has established quality control parameters to identify synovial fluid aspirates that are highly diluted by saline or blood, which appear to degrade the diagnostic performance of synovial fluid laboratory tests.

QUESTIONS/PURPOSES

(1) What proportion of synovial fluid aspirates analyzed at one laboratory are of poor quality (defined as having a red blood count > 1M cells/uL or an optical density at 280 nm < 0.324 or > 1.19)? (2) Does a poor-quality aspirate decrease the sensitivities of International Consensus Meeting-based scores and other synovial fluid biomarker tests in terms of their ability to anticipate a positive culture?

METHODS

From January 2016 to July 2019, a total of 123,549 synovial fluid samples were submitted to one laboratory for the purpose of diagnostic testing. Of these, 14% (16,773 of 123,549) samples were excluded because they were from a site other than a hip, knee, or shoulder arthroplasty, and an additional 33% (35,660 of 106,776) were excluded due to insufficient requested tests, resulting in 58% (71,116 of 123,549) samples included in this study. Specimens diluted with extreme levels of saline or blood were identified (defined as having a red blood count >1 M cells/uL or an optical density at 280 nm < 0.324 or > 1.19) as poor-quality aspirates. The sensitivities of synovial fluid C-reactive protein, alpha defensin, neutrophil elastase, white blood cell count, polymorphonuclear cell percentage, and the 2018 ICM-based tool were assessed in good-quality versus poor-quality synovial fluid samples. To avoid bias from using these evaluated tests within the reference definition of PJI in this study, a positive culture resulting from the synovial fluid served as the reference diagnosis defining a control cohort of PJI-positive samples. Although the low false-positive rate of synovial fluid culture allows for the valid estimation of synovial fluid test sensitivity, the high false-negative rate of synovial fluid culture prevents the valid estimation of test specificity, which was not evaluated in this study.

RESULTS

Of the samples analyzed, 8% (6025 of 71,116) were found to have poor quality, in that they were substantially compromised by saline and/or blood. The sensitivity of all tests to detect culture-positive synovial fluid was lower in poor-quality than in good-quality samples: 2018 International Consensus Meeting-based tool (83% [95% CI 80 to 86] versus 97% [95% CI 96 to 97]), synovial fluid C-reactive protein (65% [95% CI 61 to 69] versus 88% [95% CI 87 to 89]), alpha defensin (70% [95% CI 66 to 73] versus 93% [95% CI 93 to 94]), neutrophil elastase (80% [95% CI 77 to 83] versus 96% [95% CI 96 to 97]), synovial fluid white blood cell count (69% [95% CI 65 to 73] versus 93% [95% CI 93 to 94]), and the polymorphonuclear cell percentage (88% [95% CI 85 to 91] versus 95% [95% CI 94 to 95]), with all p < 0.001.

CONCLUSIONS

When synovial fluid is substantially diluted with saline or blood, the biomarkers and cells being measured are also diluted, decreasing the sensitivity of laboratory testing. We recommend that future diagnostic studies exclude these samples because an artificial reduction in test sensitivity will be observed.

CLINICAL RELEVANCE

Clinicians should avoid relying on negative synovial fluid testing to rule out PJI when the fluid submitted is substantially constituted of saline or blood. Further studies are necessary to understand the diagnostic utility, if any, of these diluted aspirate samples.

Is Procalcitonin (PCT) a reliable biomarker for preoperative diagnosing of low grade periprosthetic joint infection? A prospective study

BACKGROUND

Since a "gold-standard" is missing, diagnosing periprosthetic joint infection (PJI) remains a challenge in orthopedic surgery. The purpose of this study was to evaluate the accuracy of serum and synovial fluid Procalcitonin (S-PCT and SF-PCT) as a diagnostic parameter and to compare it to the biomarkers recommended in the 2018 Definition of periprosthetic hip and knee infection.

METHODS

Between August 2018 and July 2019, a prospective cohort study was conducted in 70 patients with painful hip, shoulder and knee arthroplasty. Besides medical history, clinical and laboratory data was gathered. PJI was diagnosed based on the 2018 Definition of periprosthetic hip and knee infection. Preoperative blood and synovial joint fluid were taken for PCT measurement. S-PCT and SF-PCT levels were measured using standard quantitative PCT enzyme immunoassays.

RESULTS

Twenty three patients (33%) were classified as the PJI group and fourty seven patient (67%) as the aseptic group. The mean levels of S-PCT were significantly (p <  0.001) higher in the PJI group than those in the aseptic group (PJI 0.05 ± 0.21 ng/mL (0.0-1.03) vs. aseptic 0.02 ± 0.03 ng/mL (0.0-0.18)). In synovial fluid, the mean PCT values in the aseptic group were significantly higher (p <  0.001) than those of PJI group (PJI 2.7 ± 1.4 ng/mL (0.53-9.7) vs. aseptic 8.7 ± 2.5 ng/mL (0.25-87.9)). S- PCT, with a cut-off level of 0.5 ng/mL, had a sensitivity of 13.0% and a specificity of 91.0%. SF-PCT, with a cut-off level of 5.0 ng/mL, had a sensitivity of 13.0% and a specificity of 52.0%.

CONCLUSION

S-PCT and SF-PCT appeared to be no reliable biomarkers in the differential diagnosis of PJI from aseptic loosening in total joint arthroplasty.

Diagnosis of peripheral bone and prosthetic joint infections: overview on the consensus documents by the EANM, EBJIS, and ESR (with ESCMID endorsement)

OBJECTIVES

Peripheral bone infection (PBI) and prosthetic joint infection (PJI) are two different infectious conditions of the musculoskeletal system. They have in common to be quite challenging to be diagnosed and no clear diagnostic flowchart has been established. Thus, a conjoined initiative on these two topics has been initiated by the European Society of Radiology (ESR), the European Association of Nuclear Medicine (EANM), the European Bone and Joint Infection Society (EBJIS), and the European Society of Clinical Microbiology and Infectious Diseases (ESCMID). The purpose of this work is to provide an overview on the two consensus documents on PBI and PJI that originated by the conjoined work of the ESR, EANM, and EBJIS (with ESCMID endorsement).

METHODS AND RESULTS

After literature search, a list of 18 statements for PBI and 25 statements for PJI were drafted in consensus on the most debated diagnostic challenges on these two topics, with emphasis on imaging.

CONCLUSIONS

Overall, white blood cell scintigraphy and magnetic resonance imaging have individually demonstrated the highest diagnostic performance over other imaging modalities for the diagnosis of PBI and PJI. However, the choice of which advanced diagnostic modality to use first depends on several factors, such as the benefit for the patient, local experience of imaging specialists, costs, and availability. Since robust, comparative studies among most tests do not exist, the proposed flowcharts are based not only on existing literature but also on the opinion of multiple experts involved on these topics.

KEY POINTS

• For peripheral bone infection and prosthetic joint infection, white blood cell and magnetic resonance imaging have individually demonstrated the highest diagnostic performance over other imaging modalities. • Two evidence- and expert-based diagnostic flowcharts involving variable combination of laboratory tests, biopsy methods, and radiological and nuclear medicine imaging modalities are proposed by a multi-society expert panel. • Clinical application of these flowcharts depends on several factors, such as the benefit for the patient, local experience, costs, and availability.

Diagnosing Prosthetic Joint Infections in Patients With Inflammatory Arthritis: A Systematic Literature Review

BACKGROUND

Patients with inflammatory arthritis (IA) are at increased risk of prosthetic joint infections (PJI), yet differentiating between septic and aseptic failure is a challenge. The aim of our systematic review is to evaluate synovial biomarkers and their efficacy at diagnosing PJI in patients with IA.

METHODS

A comprehensive literature search was performed in the following databases from inception to January 2018: Ovid MEDLINE, Ovid EMBASE, and the Cochrane Library. Searches across the databases retrieved 367 results. Two of 5 reviewers independently screened a total of 298 citations. Discrepancies were resolved by a third reviewer. Twenty articles fit our criteria, but due to methodological differences findings could not be pooled for meta-analysis. For 5 studies, raw data were provided, pooled, and used to derive optimal diagnostic cut points.

RESULTS

Our final analysis included 1861 non-IA patients, including 426 patients with PJI, and 90 IA patients of whom 26 had PJI. There was a significant difference among the 4 groups for serum C-reactive protein (CRP), erythrocyte sedimentation rate, and synovial CRP, polymorphonuclear neutrophil percent, white blood cells, interleukin (IL)-6, IL-8, and IL-1b. Polymorphonuclear neutrophil percent had the highest sensitivity (95.2%) and specificity (85.0%) to detect infections with an optimum threshold of 78%.

CONCLUSION

While levels of synovial white blood cells, IL-6, IL-8, and serum CRP appear higher in patients with IA, there is overlap with those who are not infected. Further studies are needed to explore diagnostic tests that will better detect PJI in patients with IA.

Synovial C-reactive protein features high negative predictive value but is not useful as a single diagnostic parameter in suspected periprosthetic joint infection (PJI)

OBJECTIVES

Synovial fluid C-reactive protein (syCRP) has been recently described as a new biomarker in preoperative diagnostics to identify periprosthetic joint infections (PJI). The aim of this study was to evaluate syCRP in a large cohort of patients with suspected PJI and to calculate the optimal cut-off to diagnose PJI.

METHODS

Between September 2015 and June 2017, we prospectively included patients with suspected PJI, in which syCRP was additionally measured along with routine preoperative diagnostic serum and synovial biomarkers. We analysed the sensitivity and specificity of syCRP using receiver operating characteristic curves.

RESULTS

We included 192 cases (hip n = 80, knee n = 91, shoulder n = 21) with a final diagnosis of PJI in 26 cases (14.0%). Combined for all joints, the syCRP values were significantly higher in the PJI group than in the no PJI group (median: 13.8 vs. 0 mg/l; p < 0.001). The optimal cut-off (Youden Index: 0.71) for the PJI diagnosis combined for all joints was at a syCRP value of 2.9 mg/l with a sensitivity of 88%, a specificity of 82%, and a negative predictive value of 98%.

CONCLUSIONS

SyCRP features high negative predictive value but is not useful as a single diagnostic parameter in suspected periprosthetic joint infection (PJI).

Diagnostic Accuracy of Serum, Synovial, and Tissue Testing for Chronic Periprosthetic Joint Infection After Hip and Knee Replacements: A Systematic Review

BACKGROUND

Chronic periprosthetic joint infection (PJI) is a devastating complication that can occur following total joint replacement. Patients with chronic PJI report a substantially lower quality of life and face a higher risk of short-term mortality. Establishing a diagnosis of chronic PJI is challenging because of conflicting guidelines, numerous tests, and limited evidence. Delays in diagnosing PJI are associated with poorer outcomes and morbid revision surgery. The purpose of this systematic review was to compare the diagnostic accuracy of serum, synovial, and tissue-based tests for chronic PJI.

METHODS

This review adheres to the Cochrane Collaboration's diagnostic test accuracy methods for evidence searching and syntheses. A detailed search of MEDLINE, Embase, the Cochrane Library, and the grey literature was performed to identify studies involving the diagnosis of chronic PJI in patients with hip or knee replacement. Eligible studies were assessed for quality and bias using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. Meta-analyses were performed on tests with sufficient data points. Summary estimates and hierarchical summary receiver operating characteristic (HSROC) curves were obtained using a bivariate model.

RESULTS

A total of 12,616 citations were identified, and 203 studies met the inclusion criteria. Of these 203 studies, 170 had a high risk of bias. Eighty-three unique PJI diagnostic tests were identified, and 17 underwent meta-analyses. Laboratory-based synovial alpha-defensin tests and leukocyte esterase reagent (LER) strips (2+) had the best performance, followed by white blood-cell (WBC) count, measurement of synovial C-reactive protein (CRP) level, measurement of the polymorphonuclear neutrophil percentage (PMN%), and the alpha-defensin lateral flow test kit (Youden index ranging from 0.78 to 0.94). Tissue-based tests and 3 serum tests (measurement of interleukin-6 [IL-6] level, CRP level, and erythrocyte sedimentation rate [ESR]) had a Youden index between 0.61 to 0.75 but exhibited poorer performance compared with the synovial tests mentioned above.

CONCLUSIONS

The quality of the literature pertaining to chronic PJI diagnostic tests is heterogeneous, and the studies are at a high risk for bias. We believe that greater transparency and more complete reporting in studies of diagnostic test results should be mandated by peer-reviewed journals. The available literature suggests that several synovial fluid-based tests perform well for diagnosing chronic PJI and their use is recommended in the work-up of any suspected case of chronic PJI.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Consensus document for the diagnosis of prosthetic joint infections: a joint paper by the EANM, EBJIS, and ESR (with ESCMID endorsement)

Background

For the diagnosis of prosthetic joint infection, real evidence-based guidelines to aid clinicians in choosing the most accurate diagnostic strategy are lacking.

Aim and Methods

To address this need, we performed a multidisciplinary systematic review of relevant nuclear medicine, radiological, orthopaedic, infectious, and microbiological literature to define the diagnostic accuracy of each diagnostic technique and to address and provide evidence-based answers on uniform statements for each topic that was found to be important to develop a commonly agreed upon diagnostic flowchart.

Results and Conclusion

The approach used to prepare this set of multidisciplinary guidelines was to define statements of interest and follow the procedure indicated by the Oxford Centre for Evidence-based Medicine (OCEBM).

Electronic supplementary material

The online version of this article (10.1007/s00259-019-4263-9) contains supplementary material, which is available to authorized users.

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

PURPOSE

(1) To determine the overall accuracy of synovial alpha-defensin, synovial C-reactive protein (sCRP), interleukin-6 (sIL-6), and leukocyte esterase (sLE) as diagnostic markers for periprosthetic joint infection (PJI) and (2) to independantly evaluate the accuracy of both the laboratory-based ELISA alpha-defensin test and the Synovasure™ alpha-defensin test kit.

METHODS

An EMBASE and MEDLINE (PubMed) database search was performed using a set of professionally set search terms. Two independent reviewers rated eligible articles. Sensitivity and specificity were meta-analysed using a bivariate random-effects model.

RESULTS

Accuracy values were extracted from 42 articles. Pooled sensitivity and specificity of the represented biomarkers were: alpha-defensin ELISA 0.97 (95% CI 0.91-0.99) and 0.97 (95% CI 0.94-0.98), respectively; Synovasure™ test kit assay 0.80 (95% CI 0.65-0.89) and 0.89 (95% CI 0.76-0.96), respectively; sLE 0.79 (95% CI 0.67-0.87) and 0.92 (95% CI 0.87-0.92), respectively; sIL-6 0.76 (95% CI 0.65-0.84) and 0.91 (95% CI 0.88-0.94), respectively; sCRP 0.86 (95% CI 0.81-0.91) and 0.90 (95% CI 0.86-0.93), respectively.

CONCLUSION

The labararory-based alpha-defensin ELISA test showed the highest ever reported accuracy for PJI diagnosis. However, this did not apply for the Synovasure™ alpha-defensin test, which was comparable in its overall diagnostic accuracy to sCRP, sIL-6 and sLE. The later biomarkers also did not yield an overall diagnostic accuracy higher than that previously reported for synovial white cell count (sWBC) or culture bacteriology. Based on current evidence, no synovial biomarker should be applied as a standalone diagnostic tool. Furthermore, the use of the laboratory-based alpha-defensin ELISA test should be encouraged, still, the Synovasure™ alpha-defensin test kit should be critically appreciated.

LEVER OF EVIDENCE

III.

Elevation of fibrin degradation product (FDP) values prevents the negative conversion of serum CRP values after total knee arthroplasty

Background

It is essential as an orthopedic surgeon to diagnose prosthetic joint infection (PJI) at an early stage and to carry out precise treatment as well as preventing the deterioration of functional prognosis as much as possible. We suspected that PJI might have been caused because the negative conversion of creatinine reactive protein (CRP) has been prolonged after total knee arthroplasty (TKA) and patients with no serum CRP negative conversion have been treated with antibiotics to avoid the morbidity of PJI. The purpose of the present study is to investigate the factors associated with prolongation of the negative conversion of CRP, with the exclusion of PJI patients.

Methods

We performed a retrospective case control study at our institution from August 2014 to August 2016. We classified the patients into two groups based on whether it required ≥20 days (Group A, n = 23) or <20 days (Group B, n = 23) for CRP levels to normalize. Serum D-Dimer and fibrin degradation product (FDP) values were measured at 1, 2, 5, 9, 12, 16, 19, 23, 26, and 30 days after TKA. Exclusion criteria include anticoagulant oral administration cases before TKA, venous thromboembolism (VTE) by postoperative lower limb venous echocardiography before and after TKA, CRP re-elevation cases, and patients with PJI. The cutoff points for D-dimer and FDP levels for screening tests were calculated from the receiver operating characteristic (ROC) curve.

Results

The ROC analysis of D- Dimer values at 30 days after TKA yielded an AUC of 0.891 (95% confidence interval (CI) 0.858-1.000), which indicates nearly an excellent test. The cutoff point of 22.1 μg/dl for FDP value (Younden Index: 22.1 μg/dl) showed a sensitivity of 81.8% (95% CI 70.1-92.8) and a specificity of 80.0% (95% CI 67.9-89.1).

Conclusion

We revealed that CRP values of patient with an FDP level ≥22.1 μg/dl at 30 days after TKA necessarily showed negative conversion without antibiotic administration, when examining a patient with elevated serum CRP of minor criteria in the definition of PJI proposed by MSIS (other criteria do not apply).

Level of evidence

Ⅲ.

Serum IL-6 in combination with synovial IL-6/CRP shows excellent diagnostic power to detect hip and knee prosthetic joint infection

BACKGROUND

The diagnosis of prosthetic joint infection (PJI) is still a challenge in some patients after total joint replacement. Interleukin-6 (IL-6) strongly participates in the arrangement of the host-bacteria response. Therefore, increased levels of IL-6 should accompany every PJI.

PURPOSE

The aim of the study was to show diagnostic characteristics of serum IL-6 for the diagnosis of prosthetic joint infection (PJI). We also compared the diagnostic values of serum IL-6 with synovial IL-6 (sIL-6) and synovial C-reactive protein (sCRP).

STUDY DESIGN

We performed a prospective study of 240 patients in whom serum IL-6 was determined before total hip (n = 124) or knee (n = 116) reoperations. The PJI diagnosis was based on the MSIS (Musculoskeletal Infection Society) criteria (2011). Receiver operating characteristic plots were constructed for IL-6, sIL-6, and sCRP.

RESULTS

PJI was diagnosed in 93 patients, and aseptic revision was diagnosed in 147 patients. The AUC (area under curve) for IL-6 was 0.938 (95% CI; 0.904-0.971). The optimal IL-6 cut-off value for PJI was 12.55 ng/L. Positive and negative likelihood ratios for IL-6 were 8.24 (95% CI; 4.79-14.17) and 0.15 (95% CI; 0.09-0.26), respectively. The optimal sIL-6 and sCRP cut-off values were 20,988 ng/L and 8.80 mg/L, respectively. Positive and negative likelihood ratios for sIL-6 were 40.000 (95% CI; 5.7-280.5) and 0.170 (95% CI; 0.07-0.417), respectively. Negative likelihood ratio for sCRP was 0.083 (95% CI; 0.022-0.314).

CONCLUSIONS

The present study identified the cut-off values for serum/synovial IL-6 and synovial CRP for diagnostics of PJI at the site of THA and TKA and separately for each site. The diagnostic odds ratio for serum/synovial IL-6 and synovial CRP is very good. Simultaneous positivity of serum IL-6 either with synovial IL-6 or synovial CRP almost excludes false negative detection of PJI at the site of interest.

Histopathology in Periprosthetic Joint Infection: When Will the Morphomolecular Diagnosis Be a Reality?

The presence of a polymorphonuclear neutrophil infiltrate in periprosthetic tissues has been shown to correlate closely with the diagnosis of septic implant failure. The histological criterion considered by the Musculoskeletal Infection Society to be diagnostic of periprosthetic joint infection is “greater than five neutrophils per high-power field in five high-power fields observed from histologic analysis of periprosthetic tissue at ×400 magnification.” Surgeons and pathologists should be aware of the qualifications introduced by different authors during the last years in the histological techniques, samples for histological study, cutoffs used for the diagnosis of infection, and types of patients studied. Recently, immunohistochemistry and histochemistry studies have appeared which suggest that the cutoff point of five polymorphonuclear neutrophils in five high-power fields is too high for the diagnosis of many periprosthetic joint infections. Therefore, morphomolecular techniques could help in the future to achieve a more reliable histological diagnosis of periprosthetic joint infection.

Diagnosis of Prosthetic Joint Infection: Cultures, Biomarker and Criteria

Prosthetic joint infections (PJIs) are devastating complications after joint arthroplasty that continue to pose a diagnostic challenge. Currently, a single, stand-alone test with the adequate accuracy and reliability for diagnosis of PJI is not available; therefore, physicians who care for patients with PJI must rely on a combination of diagnostic tests for the diagnosis of PJI. This article reviews conventional laboratory test modalities, diagnostic accuracy and limitations of current tests, and novel emerging tests for the diagnosis of PJI.

Tertiary care centre adherence to unified guidelines for management of periprosthetic joint infections: a gap analysis

BACKGROUND

The success rate of surgical treatment for periprosthetic joint infection (PJI) remains inconsistent in the literature. Variability in PJI clinical guidelines and surgeon adherence to guidelines could affect treatment success. The objectives of this study were to appraise current recommendations for PJI management and develop a unified clinical standard of care, to perform a gap analysis of PJI cases in a tertiary institution to determine the rate of guideline adherence, and to determine if adherence to unified PJI guidelines affected 2-year treatment outcomes.

METHODS

We appraised the PJI guidelines from 3 academic medical societies, and consistent statements were aggregated. We retrospectively reviewed all PJI cases in a tertiary care institution. We defined PJI based on Musculoskeletal Infection Society PJI criteria. Surgeon adherence to preoperative, intraoperative, surgical and medical management guidelines was calculated, and we evaluated the association between guideline adherence and 2-year treatment outcomes.

RESULTS

The institutional rate of PJI was 1.13% (38 of 3368). Treatment success was 57.8% at 2 years. Unified guideline adherence percentages varied substantially: 92% of patients had preoperative erythrocyte sedimentation rate and C-reactive protein, 97% had intraoperative tissue cultures, 42% had appropriate preoperative arthrocentesis, and 74% underwent guideline-appropriate surgery. Performing appropriate preoperative arthrocentesis significantly correlated with positive treatment outcomes at 2 years (p = 0.028).

CONCLUSION

Adherence to PJI guidelines varies considerably, indicating that clinicians are either unaware of them or do not recognize their value for PJI treatment. This study shows the need for institution-based PJI treatment pathways that are consistent with published guidelines and the need to monitor adherence.

Synovial Fluid Biomarkers for the Diagnosis of Periprosthetic Joint Infection: A Systematic Review and Meta-Analysis

BACKGROUND

The search for a single standard reference test for determining periprosthetic joint infection (PJI) through analysis of synovial fluid has yielded numerous biomarkers as potential candidates. The purpose of the present systematic review and meta-analysis was to evaluate the diagnostic accuracy of synovial fluid biomarkers and to determine which test has the highest diagnostic odds ratio (DOR) for the diagnosis of PJI.

METHODS

An online literature search of the MEDLINE, Embase, and Cochrane databases identified 33 articles reporting a total of 13 major parameters for diagnosing PJI through analysis of synovial fluid. Each of the included articles was independently analyzed for risk of bias and for concerns regarding applicability utilizing the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies-2) tool. The mada (meta-analysis of diagnostic accuracy) tool was used to generate forest plots for sensitivity, specificity, and the log of the DOR, as well as summary statistics.

RESULTS

In this analysis, 13 index tests (leukocyte count; measurement of the percentage of polymorphonucleocytes [PMN%] and the levels of C-reactive protein [CRP], α-defensin, leukocyte esterase [LE], interleukin [IL]-6, IL-8, IL-10, IL-1β, vascular endothelial growth factor [VEGF], and granulocyte-colony stimulating factor [G-CSF]; culture; and polymerase chain reaction [PCR] analysis) were evaluated on the basis of ≥2 articles. Of these tests, 8 (leukocyte count, PMN%, CRP, α-defensin, LE, IL-6, IL-8, and culture) were appropriate for pooled analysis. The overall sensitivity of these 8 markers was 0.85, and all but culture showed a sensitivity of ≥0.8. All markers showed a specificity of ≥0.9. Of the 8 tests, measurement of the α-defensin level showed the highest log DOR.

CONCLUSIONS

Synovial fluid leukocyte count, PMN%, CRP, α-defensin, LE, IL-6, and IL-8 all demonstrated high sensitivity for diagnosing PJI, with α-defensin being the best synovial marker based on the highest log DOR. However, other synovial fluid tests that demonstrate good diagnostic performance can also be used in combination for the diagnosis of PJI.

LEVEL OF EVIDENCE

Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Managing an Acute and Chronic Periprosthetic Infection

A case report of a 65-year-old female with a history of right total hip arthroplasty (THA) in 2007 and left THA in 2009 was presented. She consulted with our institution for the first time, on December 2013, for right hip pain and fistula on the THA incision. It was managed as a chronic infection, so a two-stage revision was performed. First-time intraoperative cultures were positive for Staphylococcus aureus (3/5) and Proteus mirabilis (2/5). Three weeks after the second half of the review, it evolved with acute fever and pain in relation to right hip. No antibiotics were used, arthrocentesis was performed, and a coagulase-negative staphylococci multisensible was isolated at the 5th day. Since the germ was different from the first revision, it was decided to perform a one-stage revision. One year after the first review, the patient has no local signs of infection and presents ESV and RPC in normal limits. The indication and management of periprosthetic infections are discussed.

The Diagnostic Utility of Synovial Fluid Markers in Periprosthetic Joint Infection: A Systematic Review and Meta-analysis

INTRODUCTION

This study is a systematic review of all reported synovial fluid markers for the diagnosis of periprosthetic joint infection and a meta-analysis of the most frequently reported markers to identify those of greatest diagnostic utility.

METHODS

A search of six databases was conducted to identify all studies evaluating the utility of synovial fluid markers in the diagnosis of periprosthetic joint infection. Two observers assessed methodologic quality and extracted data independently. A meta-analysis of the most frequently reported markers was performed.

RESULTS

Twenty-three studies were included in the meta-analysis. The most common markers (and their respective area under the curve) were interleukin-17 (0.974), leukocyte esterase (0.968), α-defensin (0.958), interleukin-6 (0.956), interleukin-1β (0.948), and C-reactive protein (0.927). Among these markers, α-defensin had the highest diagnostic odds ratio but did not achieve statistically significant superiority.

CONCLUSION

The most frequently studied synovial fluid markers for the diagnosis of periprosthetic joint infection are C-reactive protein, leukocyte esterase, interleukin-6, interleukin-1β, α-defensin, and interleukin-17, all of which have high diagnostic utility.

LEVEL OF EVIDENCE

Level II.

The Role of Biomarkers for the Diagnosis of Implant-Related Infections in Orthopaedics and Trauma

Diagnosis of implant-related (periprosthetic joint) infections poses a major challenge to infection disease physicians and orthopaedic surgeons. Conventional diagnostic tests continue to suffer from issues of accuracy and feasibility. Biomarkers are used throughout medicine for diagnostic and prognostic purposes, as they are able to objectively determine the presence of a disease or a biological state. There is increasing evidence to support the measurement of specific biomarkers in serum and/or synovial fluid of patients with suspected periprosthetic joint infections. Promising serum biomarkers include interleukin (IL)-4, IL-6, tumour necrosis factor (TNF)-α, procalcitonin, soluble intercellular adhesion molecule 1 (sICAM-1), and D-dimer. In addition to c-reactive protein and leucocyte esterase, promising biomarkers that can be measured in synovial fluid include antimicrobial proteins such as human β-defensin (HBD)-2 and human β-defensin (HBD)-3, and cathelicidin LL-37, as well as several interleukins such as IL-1β, IL-6, IL-8, IL-17, TNF- α, interferon-δ, and vascular endothelial growth factor.

Utility of Synovial White Blood Cell Count and Differential Before Reimplantation Surgery

BACKGROUND

Determining optimal timing of reimplantation during 2-stage exchange for periprosthetic joint infection (PJI) remains elusive. Joint aspiration for synovial white blood cell (WBC) count and neutrophil percentage (PMN%) before reimplantation is widely performed; yet, the implications are rarely understood. Therefore, this study investigates (1) the diagnostic yield of synovial WBC count and differential analysis and (2) the calculated thresholds for persistent infection.

METHODS

Institutional PJI databases identified 129 patients undergoing 2-stage exchange arthroplasty who had joint aspiration before reimplantation between February 2005 and May 2014. Persistent infection was defined as a positive aspirate culture, positive intraoperative cultures, or persistent symptoms of PJI-including subsequent PJI-related surgery. Receiver-operating characteristic curve was used to calculate thresholds maximizing sensitivity and specificity.

RESULTS

Thirty-three cases (33 of 129; 25.6%) were classified with persistent PJI. Compared with infection-free patients, these patients had significantly elevated PMN% (62.2% vs 48.9%; P = .03) and WBC count (1804 vs 954 cells/μL; P = .04). The receiver-operating characteristic curve provided thresholds of 62% and 640 cells/μL for synovial PMN% and WBC count, respectively. These thresholds provided sensitivity of 63% and 54.5% and specificity of 62% and 60.0%, respectively. The risk of persistent PJI for patients with PMN% >90% was 46.7% (7 of 15).

CONCLUSION

Synovial fluid analysis before reimplantation has unclear utility. Although statistically significant elevations in synovial WBC count and PMN% are observed for patients with persistent PJI, this did not translate into useful thresholds with clinical importance. However, with little other guidance regarding the timing of reimplantation, severely elevated WBC count and differential analysis may be of use.

Management of periprosthetic infections

Periprosthetic joint infection (PJI) is considered one of the most challenging complications compromising patient health and is considered an economic burden. Despite all strategies PJI prevalence is between 1%-2%. Considerable efforts have been investigated in the past decade to diminish or erradicate PJI prevalence. This article manages the definition of PJI and the new major and minor criteria from Parvizi et al Then a scientific analysis of every minor and major criteria. Multidisciplinary management is reccommended according to guidelines. A numerous of surgical options exist each and everyone with its indications, contraindications and specific antibiotic therapy regimen. Surgical options are: (1) irrigation and cleaning with retention of the prosthesis with a success rate 0%-89%; (2) single-stage revision surgery with a succes rate of > 80%; and (3) two-stage revision surgery (authors preferred method) with a succes rate of 87%. Radical treatment options like arthrodesis and amputation are reserved for specific group of patients, with a succes rate varying from 60%-100%. The future of PJI is focused on improving the diagnostic tools and to combat biofilm. The cornerstone of management consists in a rapid diagnosis and specific therapy. This article presents the most current diagnostic and treatment criteria as well as the different surgical treatment options depending on the type of infection, bacterial virulence and patient comorbidities.

Procalcitonin and α-Defensin for Diagnosis of Periprosthetic Joint Infections

BACKGROUND

Current methods to diagnose periprosthetic joint infection (PJI) before revision surgery have limited diagnostic accuracy. This meta-analysis was performed to estimate the accuracy of procalcitonin (PCT) and α-defensin for the diagnosis of PJI.

METHODS

Articles on the diagnostic value of PCT or α-defensin for PJI diagnosis were searched in the PubMed database. Sensitivity, specificity, diagnostic odds ratio, the area under the curve of summary receiver operating characteristic curves (AUC), the positive likelihood ratio, and the negative likelihood ratio were calculated to evaluate the diagnostic ability of PCT and the α-defensin test for the diagnosis of PJI.

RESULTS

The pooled sensitivities for detecting PJI using PCT and α-defensin were 0.53 (95% confidence interval [CI], 0.24-0.80) and 0.96 (95% CI, 0.85-0.99), respectively. The pooled specificities for detecting PJI using PCT and α-defensin were 0.92 (95% CI, 0.45-0.99) and 0.95 (95% CI, 0.89-0.98), respectively. The pooled diagnostic odds ratios for detecting PJI using PCT and α-defensin were 13 (95% CI, 3-70) and 496 (95% CI, 71-3456), respectively. The pooled AUCs for PCT and α-defensin were 0.76 (95% CI, 0.72-0.80) and 0.99 (95% CI, 0.97-0.99), respectively. The positive likelihood ratio and the negative likelihood ratio of PCT were 6.8 (95% CI, 1.0-48.1) and 0.51 (95% CI, 0.31-0.84), respectively, whereas those of α-defensin were 19.6 (95% CI, 8.2-46.8) and 0.04 (95% CI, 0.01-0.17), respectively.

CONCLUSION

Synovial fluid α-defensin has a great potential to diagnose PJI.

The role of biomarkers in the diagnosis of periprosthetic joint infection

The role of serum erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) as the first line for evaluating a patient with periprosthetic joint infection (PJI) has been debunked.We are living in the era of biomarkers for the diagnosis of PJI, and to that effect, several biomarkers have been introduced such as synovial fluid alpha defensin and leukocyte esterase.The synovial fluid leukocyte esterase test has a low cost, is accessible, and has provided promising results for diagnosing PJI.There is an urgent need for an accurate and reliable serum biomarker for diagnosing patients with PJI. Cite this article: Shahi A, Parvizi J. The role of biomarkers in the diagnosis of periprosthetic joint infection. EFORT Open Rev 2016;1:275-278. DOI: 10.1302/2058-5241.1.160019.

Improving the accuracy of synovial fluid analysis in the diagnosis of prosthetic joint infection with simple and inexpensive biomarkers

Aims

The aims of this study were to increase the diagnostic accuracy of the analysis of synovial fluid in the differentiation of prosthetic joint infection (PJI) by the addition of inexpensive biomarkers such as the levels of C-reactive protein (CRP), adenosine deaminase (ADA), alpha-2-macrogloblulin (α2M) and procalcitonin.

Patients and Methods

Between January 2013 and December 2015, synovial fluid and removed implants were requested from 143 revision total joint arthroplasties. A total of 55 patients met inclusion criteria of the receipt of sufficient synovial fluid, tissue samples and removed implants for analysis. The diagnosis of PJI followed the definition from a recent International Consensus Meeting to create two groups of patients; septic and aseptic. Using receiver operating characteristic curves we determined the cutoff values and diagnostic accuracy for each marker.

Results

There were 23 PJIs and 32 patients with aseptic loosening. The levels of total leucocyte count, proportion of polymorphonuclear leucocytes (PMNs), CRP, ADA and α2M in the synovial fluid were all significantly higher in those with a PJI than in those with aseptic loosening. The levels of procalcitonin were comparable in the two groups. Cutoff values for the optimal performance in the diagnosis of infection were: total leucocyte count > 1463 cells/μL (sensitivity (Sens) 100%, specificity (Spec) 71.9%, positive predictive value (PPV) 71.9%, negative predictive value (NPV) 100%); proportion of PMNs > 81% (Sens 78.3%, Spec 75.0%, PPV 69.2%, NPV 82.8%); CRP > 6.7mg/L (Sens 78.3%, Spec 93.8%, PPV 90.0%, NPV 85.7%); ADA > 61U/L (Sens 78.3%, Spec 96.9%, PPV 94.7%, NPV 86.1%) and α2M > 958 mg/L (Sens 47.8%, Spec 96.9%, PPV 91.7%, NPV 72.1%). The addition of a raised level of CRP or ADA to the total leukocyte count increased the specificity: total leukocyte count > 1463 cells/μL and CRP > 6.7mg/L (Sens 78.3%, Spec 100%, PPV 100%, NPV 86.5%) or with ADA > 61U/L (Sens 78.3%, Spec 96.9%, PPV 94.7%, NPV 86.1%).

Conclusion

The total leucocyte count in the synovial fluid offers great negative predictive value in the diagnosis of PJI and the addition of more specific markers such as CRP and ADA improves the positive predictive value. Thus the addition of simple and inexpensive markers to the measurement of the leucocyte count in the synovial fluid may reduce the number of equivocal results which demand more expensive investigation. Cite this article: Bone Joint J 2017;99-B:351–7.

Synovial Fluid C-reactive Protein as a Diagnostic Marker for Periprosthetic Joint Infection: A Systematic Review and Meta-analysis

Background:

Periprosthetic joint infection (PJI) is the main cause of failure following total joint arthroplasty. Until now, the diagnosis of PJI is still confronted with technical limitations, and the question of whether synovial fluid biomarker, C-reactive protein (CRP), can provide high value in the diagnosis of PJI remains unanswered and, therefore, was the aim of the study.

Methods:

First, we conducted a systematic review on CRP in the diagnosis of PJI by searching online databases using keywords such as “periprosthetic joint infection”, “synovial fluid”, and “C-reactive protein”. Eligible studies providing sufficient data to construct 2 × 2 contingency tables were then selected based on the list of criteria and the quality of included studies was assessed subsequently. Finally, the reported sensitivity, specificity, diagnostic odds ratio (DOR), summary receiver operating characteristic (SROC) curve, and the area under the SROC (AUSROC) were pooled together and used to evaluate overall diagnostic performance.

Results:

Seven studies were included in our review, six of which comprising a total of 456 participants were further investigated in our meta-analysis. The pooled sensitivity, specificity, and DOR were 0.92 (95% confidence interval [CI]: 0.86–0.96), 0.90 (95% CI: 0.87–0.93), and 101.40 (95% CI: 48.07–213.93), respectively. The AUSROC was 0.9663 (standard error, 0.0113).

Conclusions:

Synovial fluid CRP is a good biomarker for the diagnosis of PJI with high sensitivity and specificity.

The Fate of Revision Total Knee Arthroplasty With Preoperative Abnormalities in Either Sedimentation Rate or C-Reactive Protein

BACKGROUND

Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are important markers in the evaluation and treatment of painful total knee arthroplasty (TKA). Elevation of both markers usually occurs with infected TKAs while a normal ESR and CRP usually point to aseptic causes for failure. The purpose of this study is to compare (1) rate of revision, (2) infection, and (3) reason for reoperation in a group of patients undergoing revision TKA with a single abnormality in either ESR or CRP in an otherwise negative conventional infection work-up compared to patients with normal preoperative ESR and CRP.

METHODS

We retrospectively reviewed 791 consecutive revision TKAs performed at our institution between years 2004 and 2011. Following exclusion for infection, periprosthetic fracture, prior revision TKA, positive cultures, incomplete records, and patients with less than 24-month follow-up, a total of 228 aseptic revisions (89 knees with 1 abnormal serologic marker) were available for final analysis. No patients met the current established criteria for infection. All knees underwent revision TKA using antibiotic-impregnated cement. The 2 groups were compared in terms of overall survivorship, infection rate, and rate and causes of subsequent aseptic revision.

RESULTS

The average follow-up was 60 months (24-110). There were no significant differences between the 2 groups in terms of age, sex, American Society of Anesthesiologists class, and Charlson comorbidity index. A preoperative abnormality of either ESR or CRP significantly increased the risk for reoperation for all reasons (odds ratio [OR], 3.2; P = .0028), infection (OR, 4.0; P = .034), and revision for aseptic loosening (OR, 3.69; P = .044). There were no differences in reoperations for any other reason. The average time to revision in the study group was 28.3 months compared to 40.0 months in the control group (P = .213).

CONCLUSION

A single abnormality in either the ESR or CRP increased the likelihood of both infection and reoperation following revision TKA. Conventional methods and criteria for infection detection may not be sufficiently sensitive or specific in these cases. Further work-up with additional modalities may help increase the confidence of aseptic failure before revision TKA.

Advancements in Diagnosing Periprosthetic Joint Infections after Total Hip and Knee Arthroplasty

Periprosthetic joint infection (PJI) is a complication of total joint arthroplasty that is challenging to diagnose. Currently, there is no "gold standard" for definite diagnosis of PJI. A multi-criteria definition has been described for PJI based on microbiology cultures, serum markers, such as erythrocyte sedimentation rate and C-reactive protein (CRP), synovial fluid biomarkers, such as leukocyte esterase and histopathology assessment of the periprosthetic tissue. The conventional serum markers are generally nonspecific and can be elevated in inflammatory conditions. Therefore, they cannot be relied on for definite diagnosis of PJI. Hence, with the use of proteomics, synovial fluid biomarkers such as α-defensin, IL-6, and CRP have been proposed as more accurate biomarkers for PJI. Current methods to culture micro-organisms have several limitations, and can be false-negative and false-positive in a considerable number of cases. In an attempt to improve culture sensitivity, diagnostic methods to target biofilms have recently been studied. The understanding of the concept of biofilms has also allowed for the development of novel techniques for PJI diagnosis, such as visualizing biofilms with fluorescent in-situ hybridization and detection of bacteria via DNA microarray. Lastly, the use of amplification-based molecular techniques has provided methods to identify specific species of bacteria that cause culture-negative PJI. While diagnosing PJI is difficult, these advances could be valuable tools for clinicians.

The C-Reactive Protein May Not Detect Infections Caused by Less-Virulent Organisms

BACKGROUND

The aim of the present study was to evaluate the influence of organism type on the performance of the synovial fluid C-reactive protein (CRP) test.

METHODS

We retrospectively reviewed the results of 21,422 synovial fluid samples sent to one common laboratory for the purpose of diagnostic testing for periprosthetic joint infection. Both a synovial fluid CRP result and a positive culture were present for 1789 submitted samples. The cultured organisms were grouped by species, virulence, and gram type; and the median CRP level was determined for each group.

RESULTS

The median synovial fluid CRP level was significantly lower for less-virulent organisms, when compared to those organisms classified as virulent (15.10 mg/L vs 32.70 mg/L; P < .0001). Some less-virulent species such as yeast and Staphylococcus epidermidis were associated with a 4-10 times lower CRP response than those of virulent organisms such as Streptococcus agalactiae and Staphylococcus aureus (P < .0001). Bacterial gram type had no influence on the median CRP result. The rate of false-negative CRP values was 50.9% for yeast, 29.4% for S. epidermidis, 28.5% for all less-virulent organisms, and 11.6% for all virulent organisms.

CONCLUSION

The CRP response appears to be highly dependent on the infecting organism and is more likely to provide false-negative results in the setting of less-virulent organisms. Although the use of a CRP level is an important part of the workup for periprosthetic joint infection, surgeons must be aware that this protein may yield a false-negative result in the setting of less-virulent organisms.

Prosthetic Device Infections

The immunocompromised host is a particularly vulnerable population in whom routine and unusual infections can easily and frequently occur. Prosthetic devices are commonly used in these patients and the infections associated with those devices present a number of challenges for both the microbiologist and the clinician. Biofilms play a major role in device-related infections, which may contribute to failed attempts to recover organisms from routine culture methods. Moreover, device-related microorganisms can be difficult to eradicate by antibiotic therapy alone. Changes in clinical practice and advances in laboratory diagnostics have provided significant improvements in the detection and accurate diagnosis of device-related infections. Disruption of the bacterial biofilm plays an essential role in recovering the causative agent in culture. Various culture and nucleic acid amplification techniques are more accurate to guide directed treatment regimens. This chapter reviews the performance characteristics of currently available diagnostic assays and summarizes published guidelines, where available, for addressing suspected infected prosthetic devices.

Outcomes in the treatment of periprosthetic joint infection after shoulder arthroplasty: a systematic review

BACKGROUND

Although many case series have been published on the treatment of shoulder periprosthetic joint infection (PJI), few provide direct comparison of outcomes. This systematic review synthesizes the available English literature on shoulder PJI to quantify treatment effectiveness.

METHODS

The PubMed and Embase databases were searched in April 2014. Keywords included "shoulder replacement infection" and "shoulder arthroplasty infection." Of 663 titles, 55 manuscripts underwent full-text review after application of exclusion criteria. Thirty articles were finally included.

RESULTS

Propionibacterium acnes was most commonly reported, representing 38.9% of infections, followed by Staphylococcus species. Risk factors for shoulder PJI include previous surgery, increased age, male gender, increased body mass index, and diabetes mellitus. The average white blood cell count in 13 studies was 7472 cells/µL. Ten studies reported a mean erythrocyte sedimentation rate of 27.6 mm/h, whereas 14 studies reported a mean C-reactive protein level of 2.6 mg/dL. P. acnes in intraoperative culture specimens was an independent risk factor for failed treatment for shoulder PJI. When outcomes were pooled, no statistical difference was found in the success rates of 1-stage, 2-stage, or resection arthroplasty revision; each displayed a success rate >90%. However, single-stage revision produced the highest mean Constant score; implant retention resulted in the best range of motion.

CONCLUSIONS

Our data suggest that single-stage revision can be as effective as 2-stage or resection treatments; however, the retrospective nature of these data precluded our ability to control for confounding variables. Future studies on shoulder PJI should involve direct comparisons of 1-stage vs. 2-stage treatment while comparing cost, morbidity, and functional outcomes.