How Reliable Is the Cell Count Analysis in the Diagnosis of Prosthetic Joint Infection?

Synovial Calprotectin is Superior to Synovial Leukocyte Count in Excluding Chronic Periprosthetic Joint Infections, a Retrospective Cohort Study

BACKGROUND

Synovial calprotectin is a promising biomarker for diagnosing chronic periprosthetic joint infections (PJIs), but its diagnostic value has not been directly compared to synovial leukocyte count and polymorphonuclear neutrophils. This study aimed to: (1) evaluate and compare the diagnostic accuracy between these markers in patients undergoing revision arthroplasty for chronic PJI or aseptic reasons; and (2) determine the best rule-out and rule-in test for PJI.

METHODS

Synovial fluid samples from patients undergoing revision arthroplasty in hip and knee joints were collected and analyzed. Patients diagnosed with an acute PJI, patients treated with antibiotics 2 weeks prior to revision surgery, and/or patients who had active inflammatory joint disease were excluded. Periprosthetic joint infections were diagnosed based on the presence of a sinus tract and/or positive intraoperative cultures according to the European Bone and Joint Infection Society microbiological criteria.

RESULTS

A total of 137 patients were included, of whom 19 (14%) were diagnosed with a PJI. Overall, synovial calprotectin had the highest diagnostic accuracy of all studied markers (area under the curve 96%). Synovial calprotectin, with a cutoff of 50 mg/L, had the highest negative predictive value of 100%. However, PMNs (> 80%) combined with a leukocyte count (> 3,000 cells/μL) showed the highest positive likelihood ratio of an infection (PLR 17).

CONCLUSIONS

Synovial calprotectin is the most accurate biomarker for ruling out a chronic PJI, while the combination of synovial leukocyte count and PMN is most reliable for ruling in a chronic PJI.

An overview of the current diagnostic approach to Periprosthetic Joint Infections

The diagnosis of periprosthetic joint infections (PJI) presents a formidable challenge to orthopaedic surgeons due to its complex and diverse manifestations. Accurate diagnosis is of utmost importance, as even mild pain following joint replacement surgery may indicate PJI in the absence of a definitive gold standard diagnostic test. Numerous diagnostic modalities have been suggested in the literature, and international societies have continually updated diagnostic criteria for this debilitating complication. This review article aims to comprehensively examine the latest evidence-based approaches for diagnosing PJI. Through a thorough analysis of current literature, we explore promising diagnostic strategies that have demonstrated effectiveness in identifying PJI. These strategies encompass the utilization of laboratory markers, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), alongside imaging techniques such as magnetic resonance imaging (MRI) and leukocyte scintigraphy. Additionally, we highlight the importance of synovial fluid analysis, including the potential role of alpha-defensin as a biomarker, and examine evolving international diagnostic criteria to standardize and improve diagnostic accuracy.

Current Status and Perspectives of Diagnosis and Treatment of Periprosthetic Joint Infection

Periprosthetic joint infection (PJI) is a catastrophic complication following joint replacement surgery, posing significant challenges to orthopedic surgeons. Due to the lack of a definitive diagnostic gold standard, timely treatment initiation is problematic, resulting in substantial economic burdens on patients and society. In this review, we thoroughly analyze the complexities of PJI and emphasize the importance of accurate diagnosis and effective treatment. The article specifically focuses on the advancements in diagnostic techniques, ranging from traditional pathogen culture to advanced molecular diagnostics, and discusses their role in enhancing diagnostic accuracy. Additionally, we review the latest surgical management strategies, including everything from debridement to revision surgeries. Our summary aims to provide practical information for the diagnosis and treatment of PJI and encourages further research to improve diagnostic accuracy and treatment outcomes.

How Reliable Is the Absolute Synovial Polymorphonuclear Neutrophil Cell Count in Diagnosing Periprosthetic Joint Infection?

BACKGROUND

Diagnosing periprosthetic joint infection (PJI) is a daunting task for even the most experienced orthopedic surgeons, as there is currently no test available that can provide absolute accuracy. Utilizing an established synovial indicator for detecting PJI without incurring additional costs or resources would be the optimal solution for predicting the presence of infection. Therefore, we hypothesized that synovial absolute neutrophil count (ANC) would improve the diagnostic accuracy of chronic knee and hip PJI.

METHODS

The study included 260 patients (134 men and 126 women, mean age of 70 years [range, 26 to 89]) who underwent aspiration during preoperative workup. Of these, 109 patients (41.9%) were diagnosed with chronic PJI (50 knees, 59 hips), and 151 patients (58.1%) were diagnosed as aseptic (94 knees, 57 hips). Data obtained from all patients included age, sex, procedure type (total hip or total knee arthroplasty), operation side, synovial white blood cell count (cells/μL), synovial polymorphonuclear cells percentage, and synovial α-defensin immunoassay value at the admission were retrieved from the electronic medical record.

RESULTS

The calculated optimal threshold for synovial ANC of 1,415.5 cells/μL was associated with an area under the receiver operating characteristic curve (AUC) of 0.930 for chronic knee PJI diagnosis. The calculated optimal threshold for synovial ANC of 2,247 cells/μL was associated with an AUC of 0.905 for chronic hip PJI diagnosis.

CONCLUSIONS

This study has conclusively shown that the synovial ANC serves as a valuable marker in the complicated diagnosis of PJI. This highly effective and efficient approach should be utilized for obtaining further information through standard tests, thereby ruling out the possibility of PJI.

LEVEL OF EVIDENCE

III.

Can the Current Thresholds for Synovial Cell Count and Neutrophil Percentage to Diagnose Prosthetic Joint Infection be Applied to Metal-on-Metal Rotating Hinge Total Knee Arthroplasty?

BACKGROUND

Synovial leukocyte count analysis is an important tool in the diagnosis of PJI. However, results can be poor if metallosis is present. The issue of metallosis was established for some rotating hinge knee arthroplasty designs.

METHODS

This was a retrospective single-center analysis that included 108 patients who had a single-design metal-on-metal rotating hinge knee arthroplasty who underwent revision surgery and had prior synovial fluid analysis performed. The diagnostic accuracy of leukocyte count and the percentage of polymorphonuclear neutrophiles (% PMN) were investigated.

RESULTS

Patients who had a PJI had a higher median leukocyte count and % PMN compared to aseptic revisions (7,905/μL (interquartile range (IQR) 2,419 to 37,400) and 85% (IQR 70.3 to 93.8) versus 450 (IQR 167 to 1,215) and 46% (IQR 28.5 to 67.4%), P < .001). The respective areas under the curves were 0.916 (95% confidence interval 0.862 to 0.970) for leukocyte count and 0.821 (95% confidence interval 0.739 to 0.902) for % PMN. We calculated an optimal cut-off value of 1,200 leukocytes/μL (Sensitivity 94.5%/specificity 75.5%) and 63% PMN (Sensitivity 85.5%/specificity 73.6%) to define PJI. Established thresholds were less sensitive, but more specific. The "infection likely" scenario of the European Bone and Joint Infection Society (EBJIS) definition was closest to the calculated thresholds.

CONCLUSION

Currently used thresholds for leukocyte cell count and %PMN to define PJI were less sensitive and specific in the diagnosis of PJI in metal-on-metal RHK knees. Surgeons must consider lower cut-off values when evaluating such implants for PJI.

Radiological Insights into Sacroiliitis: A Narrative Review

Sacroiliitis is the inflammation of the sacroiliac joint, the largest axial joint in the human body, contributing to 25% of lower back pain cases. It can be detected using various imaging techniques like radiography, MRI, and CT scans. Treatments range from conservative methods to invasive procedures. Recent advancements in artificial intelligence offer precise detection of this condition through imaging. Treatment options range from physical therapy and medications to invasive methods like joint injections and surgery. Future management looks promising with advanced imaging, regenerative medicine, and biologic therapies, especially for conditions like ankylosing spondylitis. We conducted a review on sacroiliitis using imaging data from sources like PubMed and Scopus. Only English studies focusing on sacroiliitis's radiological aspects were included. The findings were organized and presented narratively.

What is the diagnostic accuracy of neutrophil to lymphocyte ratio and monocyte to lymphocyte ratio in detecting acute periprosthetic joint infections? A gender-specific analysis

PURPOSE

The accurate and timely diagnosis of periprosthetic joint infection (PJI) is critical for guiding optimal treatment management and success, highlighting the requirement of readily available inexpensive serum biomarkers to increase the diagnostic accuracy for PJI. Many studies have investigated the diagnostic accuracy of neutrophil to lymphocyte ratio (NLR) and monocyte to lymphocyte ratio (MLR). However, there is a lack of existing literature regarding optimal thresholds for acute PJI. The purpose of this study was to reveal the most appropriate cut-off values for MLR and NLR in detecting acute PJI with a gender specific analysis.

METHODS

Patients were classified as having an acute PJI if they met the International Consensus Meeting (ICM) 2018 modified criteria. Patients who had a negative clinical and diagnostic workup for a PJI and the presence of erythema on the index surgical area were included in the erysipelas group (control group). Data obtained from all patients included age, sex, body mass index (BMI), Charlson Comorbidity Index (CCI), procedure type (THA or TKA), serum C-reactive protein (CRP), and blood studies at the admission and culture results were retrieved from the electronic medical record.

RESULTS

ROC curve analysis was used to determine the gender-specific optimal threshold values for CRP, NLR, and MLR. Comparing the sensitivities and specificities of NLR and MLR at the identified best thresholds in males and females, the study found similar sensitivities of NLR in males and females with 0.84 and 0.84, respectively. On the other hand, an MLR of 0.67 or more reported a notably higher specificity in male patients [0.90 (95% CI 0.75-0.96) versus 0.70 (95% CI 0.56-0.80)].

CONCLUSION

NLR and MLR represent commonly ordered, low-cost, simple, and readily available complete cell count laboratory values and should be used as adjunct tests with reasonable diagnostic accuracy in detecting acute PJIs. Moreover, with its excellent specificity and PPV, MLR could provide valuable insight in diagnosing acute PJI, particularly in male patients.

LEVEL OF EVIDENCE

Level III Retrospective Cohort analysis.

Diagnosis of periprosthetic joint infections in patients who have rheumatoid arthritis

Aims

To investigate the optimal thresholds and diagnostic efficacy of commonly used serological and synovial fluid detection indexes for diagnosing periprosthetic joint infection (PJI) in patients who have rheumatoid arthritis (RA).

Methods

The data from 348 patients who had RA or osteoarthritis (OA) and had previously undergone a total knee (TKA) and/or a total hip arthroplasty (THA) (including RA-PJI: 60 cases, RA-non-PJI: 80 cases; OA-PJI: 104 cases, OA-non-PJI: 104 cases) were retrospectively analyzed. A receiver operating characteristic curve was used to determine the optimal thresholds of the CRP, ESR, synovial fluid white blood cell count (WBC), and polymorphonuclear neutrophil percentage (PMN%) for diagnosing RA-PJI and OA-PJI. The diagnostic efficacy was evaluated by comparing the area under the curve (AUC) of each index and applying the results of the combined index diagnostic test.

Results

For PJI prediction, the results of serological and synovial fluid indexes were different between the RA-PJI and OA-PJI groups. The optimal cutoff value of CRP for diagnosing RA-PJI was 12.5 mg/l, ESR was 39 mm/hour, synovial fluid WBC was 3,654/μl, and PMN% was 65.9%; and those of OA-PJI were 8.2 mg/l, 31 mm/hour, 2,673/μl, and 62.0%, respectively. In the RA-PJI group, the specificity (94.4%), positive predictive value (97.1%), and AUC (0.916) of synovial fluid WBC were higher than those of the other indexes. The optimal cutoff values of synovial fluid WBC and PMN% for diagnosing RA-PJI after THA were significantly higher than those of TKA. The specificity and positive predictive value of the combined index were 100%.

Conclusion

Serum inflammatory and synovial fluid indexes can be used for diagnosing RA-PJI, for which synovial fluid WBC is the best detection index. Combining multiple detection indexes can provide a reference basis for the early and accurate diagnosis of RA-PJI.

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.

The optimal diagnostic cut-off of WBC and PMN counts for joint aspiration in periprosthetic joint infection is 2479/µL and 67%, respectively: ICM criteria thresholds are too high

BACKGROUND

Various organizations have published definitions for periprosthetic joint infection (PJI) with significant differences in the cut-offs of white blood cell (WBC) count and polymorphonuclear (PMN) leukocyte cells. Herein, we aim to analyze optimal cut-offs in patients which are planned to undergo a prosthesis revision and compare them with the actual published thresholds of the International Consensus Meeting (ICM) and European Bone and Joint Infection Society (EBJIS).

METHODS

A test kit was compiled in a monocentric prospective study, according to the ICM criteria (2018) and 2021 EBJIS criteria. The kit was implemented using: blood samples (including leukocyte count and C-reactive protein); samples for examining the synovial fluid (WBC count, PMN cell differentiation, microbiological culture for incubation over 14 days, alpha-defensin ELISA laboratory test, and leukocyte-esterase test). The cut-offs for WBC and PMN counts were investigated using ROC analyses and Youden index. The ICM 2018 criteria were applied, using alpha-defensin in all cases. Patients which have to undergo a prosthesis revision were included, a pre-operative joint aspiration had been performed, and the patients had been followed up prospectively.

RESULTS

405 patients were examined with the compiled test kit; 100% had a complete dataset with respect to alpha-defensin; 383 patients, according to WBC count; and 256, according to PMN cell differentiation The cut-off of 2478.89 cells/µl in the WBC count (sensitivity: 87.70%; specificity: 88.10%) and the cut-off of 66.99% in PMN differentiation showed the best accuracy (sensitivity: 86.00%; specificity: 88.80%). Other published cut-offs for WBC were tested in this cohort and showed the following accuracy: 3000/µl (EBJIS/ICM; sensitivity: 82.10%; specificity: 91.00%), 2000/µl (sensitivity: 89.60%; specificity: 83.40%), and 1500/µl (sensitivity: 91.50%; specificity: 75.00%). The published cut-offs for PMN had the following accuracy in this cohort: 80% (ICM; sensitivity: 66.3%; specificity: 96.50%), 70% (sensitivity: 82.6%; specificity: 90%), and 65% (EBJIS, sensitivity: 86%; specificity: 88.8%).

CONCLUSIONS

This study aims to improve current cut-offs for PMN- and WB-Count, even though PJI diagnosis is based on the combination of all defined tests. The optimal diagnostic cut-off of WBC and PMN counts was found to be 2479/µL and 67%, respectively, whereas ICM cut-offs in this cohort seem too high, as they provide high specificity but very low sensitivity. On the other hand, a cut-off for WBC count of 1500/µl alone would be very low, leading to low specificity and very high suspicion of PJI. The current consensus guidelines could be actualized considering these results to significantly improve the diagnostic quality.

LEVEL OF EVIDENCE

II.

Absolute synovial polymorphonuclear neutrophil cell count as a biomarker of periprosthetic joint infection

The aim of this study was to evaluate the diagnostic accuracy of the absolute synovial polymorphonuclear neutrophil cell (PMN) count for the diagnosis or exclusion of periprosthetic joint infection (PJI) after total hip (THA) or knee arthroplasty (TKA). In this retrospective cohort study, 147 consecutive patients with acute or chronic complaints following THA and TKA were included. Diagnosis of PJI was established based on the 2018 International Consensus Meeting criteria. A total of 39 patients diagnosed with PJI (32 chronic and seven acute) and 108 patients with aseptic complications were surgically revised. Using receiver operating characteristic curves and calculating the area under the curve (AUC), an optimal synovial cut-off value of 2,000 PMN/µl was determined (AUC 0.978 (95% confidence interval (CI) 0.946 to 1)). Using this cut-off, sensitivity and specificity of absolute synovial PMN count for PJI were 97.4% (95% CI 91.2 to 100) and 93.5% (95% CI 88.9 to 98.1), respectively. Positive and negative predictive value were 84.4% (95% CI 72.7 to 93.9) and 99.0% (95% CI 96.7 to 100), respectively. Exclusion of 20 patients with acute complications improved specificity to 97.9% (95% CI 94.6 to 100). Different cut-off values for THA (< 3,600 PMN/µl) and TKA (< 2,000 PMN/µl) were identified. Absolute synovial PMN count correlated strongly with synovial alpha-defensin (AD) (r = 0.759; p < 0.001). With a positive AD result, no additional PJI could be identified in any case. Absolute synovial PMN count is a widely available, rapid, cost-effective, and accurate marker in PJI diagnostics, whereas synovial AD appears to be a surrogate parameter of absolute synovial PMN count. Despite limitations in the early postoperative phase, wear, and rheumatic diseases in confirming PJI, an absolute synovial PMN count below 2,000/µl is highly suitable for ruling out PJI, with specific cut-off values for THA and TKA.

Simple and inexpensive synovial fluid biomarkers for the diagnosis of prosthetic joint infection according to the new EBJIS definition

Introduction: diagnosis of periprosthetic joint infection (PJI) is challenging, as no single test has absolute accuracy. The purpose of this study was to assess the utility of different simple synovial biomarkers in the diagnosis of PJI as defined by the European Bone and Joint Infection Society (EBJIS). Methods: we retrospectively identified all patients undergoing revision hip or knee arthroplasty from 2013 to 2019 on our prospectively maintained database. Only patients with minimum required infection diagnostic workup were included in the study. Patients with comorbidities that may influence the accuracy of synovial biomarkers were excluded. Receiver operator characteristic (ROC) curves were utilised to assess the diagnostic utility of synovial fluid white blood cell (WBC) count, polymorphonuclear leukocyte percentage (PMN %), C-reactive protein (CRP), adenosine deaminase (ADA), and alpha-2-microglobulin (A2M). Results: in total, 102 patients met the inclusion criteria. Of these, 58 were classified as infection unlikely, 8 as infection likely, and 36 as infection confirmed. Synovial WBC count (area under the curve (AUC) 0.94) demonstrated the best utility for the diagnosis of PJI, followed by PMN % (AUC 0.91), synovial CRP (AUC 0.90), ADA (AUC 0.82), and A2M (AUC 0.76). We found added value in the combined interpretation of different biomarkers. We calculated high sensitivity and negative predictive value if at least two of them are negative and high specificity and positive predictive value if at least two are elevated. Conclusion: current results show that synovial fluid investigation is a useful tool for the diagnosis of PJI, and the combined interpretation of simple and inexpensive biomarkers demonstrated improved diagnostic accuracy.

Synovial Fluid Absolute Neutrophil Count and Neutrophil-To-Lymphocyte Ratio are not Superior to Polymorphonuclear Percentage in Detecting Periprosthetic Joint Infection

BACKGROUND

Serum and synovial biomarkers are currently used to diagnose periprosthetic joint infection (PJI). Serum neutrophil-to-lymphocyte ratio (NLR) has shown promise as an inexpensive test in diagnosing infection, but there are no reports of synovial NLR or absolute neutrophil count (ANC) for diagnosing chronic PJI. The purpose of this study was to investigate the diagnostic potential of both markers.

METHODS

A retrospective review of 730 patients who underwent total joint arthroplasty and subsequent aspiration was conducted. Synovial white blood cell (WBC) count, synovial polymorphonuclear percentage (PMN%), synovial NLR, synovial ANC, serum erythrocyte sedimentation rate (ESR), serum C-reactive protein (CRP), serum WBC, serum PMN%, serum NLR, and serum ANC had their utility in diagnosing PJI examined by area-under-the-curve analyses (AUC). Pairwise comparisons of AUCs were performed.

RESULTS

The AUCs for synovial WBC, PMN%, NLR, and ANC were 0.84, 0.84, 0.83, and 0.85, respectively. Synovial fluid ANC was a superior marker to synovial NLR (P = .027) and synovial WBC (P = .003) but not PMN% (P = .365). Synovial NLR was inferior to PMN% (P = .006) but not different from synovial WBC (P > .05). The AUCs for serum ESR, CRP, WBC, PMN%, NLR, and ANC were 0.70, 0.79, 0.63, 0.72, 0.74, and 0.67, respectively. Serum CRP outperformed all other serum markers (P < .05) except for PMN% and NLR (P > .05). Serum PMN% and NLR were similar to serum ESR (P > .05).

CONCLUSION

Synovial ANC had similar performance to PMN% in diagnosing chronic PJI, whereas synovial NLR was a worse diagnostic marker. The lack of superiority to synovial PMN% limits the utility of these tests compared to established criteria.

D-lactate is a promising biomarker for the diagnosis of periprosthetic joint infection

Introduction

Reliable biomarkers for the diagnosis of periprosthetic joint infection (PJI) are of paramount clinical value. To date, synovial fluid leukocyte count is the standard surrogate parameter indicating PJI. As D-lactate is almost solely produced by bacteria, it represents a promising molecule in the diagnostic workflow of PJI evaluation. Therefore, the purpose of this study was to assess the performance of synovial fluid D-lactate for diagnosing PJI of the hip and knee.

Materials and Methods

These are preliminary results of a prospective multicenter study from one academic center. Seventy-two consecutive patients after total hip arthroplasty (THA) or total knee arthroplasty (TKA) were prospectively included. All patients received a joint aspiration in order to rule out or confirm PJI, which was diagnosed according to previously published institutional criteria. Synovial fluid D-lactate was determined spectrophotometrically at 450 nm. Receiver operating characteristic (ROC) analysis was performed to assess the diagnostic performance.

Results

Eighteen patients (25%) were diagnosed with PJI and 54 patients (75%) were classified as aseptic. Synovial fluid D-lactate showed a sensitivity of 90.7% (95% CI: 79.7%-96.9%) and specificity of 83.3% (95% CI: 58.6%-96.4%) at a cut-off of 0.04 mmol/L. The median concentration of D-lactate was significantly higher in patients with PJI than in those with aseptic conditions (0.048 mmol/L, range, 0.026-0.076 mmol/L vs. 0.024 mmol/L, range, 0.003-0.058 mmol/L, p < 0.0001). The predominat microogranisms were staphylococci, followed by streptococci and gram-negative bacteria.

Conclusion

D-lactate bears a strong potential to act as a valuable biomarker for diagnosing PJI of the hip and knee. In our study, a cutoff of 0.04 mmol/L showed a comparable sensitivity to synovial fluid leukocyte count. However, its specificity was higher compared to conventional diagnostic tools. The additional advantages of D-lactate testing are requirement of low synovial fluid volume, short turnaround time and low cost.

Cell-free Deoxyribonucleic Acid: A Potential Biomarker of Chronic Periprosthetic Knee Joint Infection

BACKGROUND

The correct diagnosis of a chronic periprosthetic joint infection (PJI) is a major challenge in clinical practice, with the "gold standard" for diagnosis yet to be established. Synovial fluid analysis has been proven to be a useful tool for that purpose. Cell-free DNA (cf-DNA) levels have been shown to be increased in several conditions such as cancer, trauma, and sepsis. Therefore, this study was designed to evaluate the potential of synovial fluid cf-DNA quantification for the diagnosis of chronic periprosthetic infections following total knee arthroplasty.

METHODS

A prospective study with patients undergoing total knee arthroplasty revision surgery for any indication was performed. PJI diagnosis was defined according to the Second International Consensus Meeting on Musculoskeletal Infection (2018) criteria. The study cohort consisted of 26 patients classified as infected and 40 as noninfected. Synovial fluid cf-DNA direct quantification by fluorescent staining was made. Sensitivity, specificity, and receiver operating characteristic curve were calculated.

RESULTS

The cf-DNA levels were significantly higher in patients who had PJIs (122.5 ± 57.2 versus 4.6 ± 2.8 ng/μL, P < .0001). With a cutoff of 15 ng/μL, the area under the receiver operating characteristic, sensitivity, and specificity of cf-DNA were 0.978, 96.2%, and 100%, respectively.

CONCLUSION

The present study has shown that cf-DNA is increased in synovial fluid of patients who have chronic PJIs. It is a promising biomarker for knee PJI diagnosis and further studies are needed to confirm its utility.

Role of Biomarkers in Periprosthetic Joint Infections

Periprosthetic joint infection (PJI) is one of the most serious complications after joint arthroplasty. The incidence rate of PJI after total joint replacement is 1-3%. Although there are different guidelines and diagnostic criteria used to diagnose PJI, diagnosing PJI is a highly difficult process for orthopedists. The current Musculoskeletal Infection Society (MSIS) criteria are widely used for the diagnosis of PJI. These criteria include results from blood/synovial fluid tests, physical examination, and histological and microbiological analyses of intra-operative samples. However, there is currently no blood or synovial test that can definitively diagnose PJI. To make a more effective diagnosis of PJI, a large number of studies have explored and continue to investigate biomarkers. This review aims to provide general information about serum and synovial markers used for the diagnosis of PJI that may be used to create a database to guide researchers in new studies.

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.

Combination of Synovial Fluid IL-4 and Polymorphonuclear Cell Percentage Improves the Diagnostic Accuracy of Chronic Periprosthetic Joint Infection

Background

Synovial fluid biomarkers have been found to improve the diagnosis of chronic periprosthetic joint infection (PJI); however, no “gold standard” exists yet. Interleukin-4 (IL-4) and polymorphonuclear cell (neutrophil) count in the synovial fluid are crucial in mediating local inflammation during bacterial infections and could be valuable biomarkers for PJI.

Methods

This prospective study was conducted to investigate the diagnostic potential of synovial fluid IL-4 (SF-IL4) and polymorphonuclear cell percentage (SF-PMN%) for chronic PJI. A total of 110 patients who underwent revision arthroplasty between January 2019 and October 2020 were enrolled, and 11 patients were excluded. Of 99 patients, 43 were classified as having PJI and 56 as having aseptic failures according to the 2013 Musculoskeletal Infections Society criteria. In all patients, SF-IL4, SF-PMN%, serum C-reactive protein (CRP), and serum erythrocyte sedimentation rate (ESR) were quantified preoperatively. The diagnostic value for each biomarker was analyzed, and optimal cutoff values were calculated.

Results

The patient demographics did not significantly vary. The area under the curve of SF-IL4 and SF-PMN% was 0.97 and 0.89, respectively, higher than that for serum ESR (0.72) and serum CRP (0.83). The combination of SF-IL4 and SF-PMN% provided higher specificity (97.0%) and accuracy (96.0%) when the cut-off values were 1.7 pg/mL and 75%, respectively.

Conclusion

SF-IL4 is a valuable biomarker for chronic PJI detection, and the combination of SF-IL4 and SF-PMN% improved the diagnostic value of chronic PJI, and further studies are needed until its clinical application.

Which International Consensus Meeting Preoperative Minor Criteria is the Most Accurate Marker for the Diagnosis of Periprosthetic Joint Infection in Hip and Knee Arthroplasty?

BACKGROUND

The accurate preoperative diagnosis of periprosthetic joint infection (PJI) is critical. The aim of this study was to evaluate the diagnostic accuracy and performance of the 2018 International Consensus Meeting (ICM) preoperative minor criteria for the diagnosis of chronic PJI in total hip and knee arthroplasty.

METHODS

We retrospectively reviewed 260 patients that underwent a revision knee or hip arthroplasty at our institution between 2015 and 2017. All major and minor 2018 ICM criteria (except erythrocyte sedimentation rate, D-dimer) were available for all patients included. Cases with at least 1 major criterion were considered as infected. Receiver operative characteristic curve analysis was performed for preoperative minor criteria.

RESULTS

The diagnostic performance of the preoperative minor criteria ranked as per the area under the curve was PMN% (0.926), alpha defensin (0.922), white blood cell count (0.916), leukocyte esterase (0.861), and serum C-reactive protein (0.860). Increasing the PMN % cutoff from 70% to 77.8% improves the diagnostic accuracy (86.5% vs 90.8%). The highest diagnostic performance was achieved by combining all 5 preoperative parameters, and at current ICM thresholds, the diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive were 93.5%, 95.4%, 92.1%, 89.7%, and 96.5%, respectively.

CONCLUSION

The diagnostic performance of preoperative minor criteria was outstanding (PMN%, alpha defensin, white blood cell count) or excellent (leukocyte esterase, serum C-reactive protein). PMN% showed the best diagnostic utility (area under the curve) and should have an increased weight-adjusted score in the ICM scoring system.

Variation of synovial fluid leucocyte cell count and polymorphonuclear percentage in patients with aseptic revision total knee arthroplasty

AIMS

Current guidelines consider analyses of joint aspirates, including leucocyte cell count (LC) and polymorphonuclear percentage (PMN%) as a diagnostic mainstay of periprosthetic joint infection (PJI). It is unclear if these parameters are subject to a certain degree of variability over time. Therefore, the aim of this study was to evaluate the variation of LC and PMN% in patients with aseptic revision total knee arthroplasty (TKA).

METHODS

We conducted a prospective, double-centre study of 40 patients with 40 knee joints. Patients underwent joint aspiration at two different time points with a maximum period of 120 days in between these interventions and without any events such as other joint aspirations or surgeries. The main indications for TKA revision surgery were aseptic implant loosening (n = 24) and joint instability (n = 11).

RESULTS

Overall, 80 synovial fluid samples of 40 patients were analyzed. The average time period between the joint aspirations was 50 days (SD 32). There was a significantly higher percentage change in LC when compared to PMN% (44.1% (SD 28.6%) vs 27.3% (SD 23.7%); p = 0.003). When applying standard definition criteria, LC counts were found to skip back and forth between the two time points with exceeding the thresholds in up to 20% of cases, which was significantly more compared to PMN% for the European Bone and Joint Infection Society (EBJIS) criteria (p = 0.001), as well as for Musculoskeletal Infection Society (MSIS) (p = 0.029).

CONCLUSION

LC and PMN% are subject to considerable variation. According to its higher interindividual variance, LC evaluation might contribute to false-positive or false-negative results in PJI assessment. Single LC testing prior to TKA revision surgery seems to be insufficient to exclude PJI. On the basis of the obtained results, PMN% analyses overrule LC measurements with regard to a conclusive diagnostic algorithm. Cite this article: Bone Jt Open 2021;2(8):566-572.

Poor performance of open incisional biopsy for the microbiological diagnosis of periprosthetic knee joint infection

The accurate preoperative diagnosis of periprosthetic joint infection (PJI) of total knee arthroplasty (TKA) can be difficult despite the use of a combination of serum and synovial markers. In such inconclusive cases, incisional open biopsy might be considered. This study investigates the usefulness of biopsies in patients with inconclusive diagnostic findings. We retrospectively identified 63 patients who underwent incisional biopsy for chronic PJI in the operation theatre following TKA revision between 2010 and 2018 after inconclusive preoperative diagnostics for PJI. In all cases, 5 independent biopsies were taken. Results from open biopsy for PJI were analyzed for diagnostic accuracy using the intraoperative results from following revision surgery as gold standard. 27 patients (43%) had a positive culture taken during biopsy. 15 cases (24%) met the diagnostic criteria for a chronic PJI. Most common organisms were Coagulase-negative staphylococci (67%) and Cutibacterium acnes (30%). Compared to the findings during revision surgery, biopsies showed a sensitivity of 47% and a specificity of 77% for PJI. Open incisional biopsy following inconclusive serum- and synovial diagnostics for low grade PJI may be considered for identification of microorganisms. Due to its low sensitivity and moderate specificity found in the present cohort, microbiological analysis should be combined with additional diagnostic markers and histological investigation.Level of Evidence. Retrospective cohort study (Level III).

Diagnosis and management of the infected total knee replacement: a practical surgical guide

PURPOSE

Prosthetic joint infection (PJI) after total knee arthroplasty (TKA) is a significant burden in health care. Diagnosis and proper management are challenging. A standardised procedure for the diagnostic workup and surgical management provides clear benefits in outcome.

METHODS

Several diagnostic protocols and definitions for PJI were established in recent years. Proper PJI diagnosis remains critical for success and for choosing the optimal treatment option. A distinct workup of diagnostic steps, the evaluation of the results in a multidisciplinary setup and the meticulous surgical management of the infection are the key factors of successful treatment.

RESULTS

The management of PJI after TKA consists of early revision with debridement and implant retention (DAIR) in early cases or staged revision in late infections beyond 30 days postoperative or after onset of acute symptoms. The revision is performed as a two-stage procedure with the use of a fixed or mobile antibiotic spacer, or in selected cases as a single-stage operation with the use of local and systemic antibiotic treatment.

CONCLUSIONS

This paper reflects the opinion of two revision surgeons who follow the same protocol for diagnosis and treatment of PJI after TKA, highlighting the key steps in diagnosis and management.

LEVEL OF EVIDENCE

Expert's opinion.

Soluble Pecam-1 as a Biomarker in Periprosthetic Joint Infection

A reliable workup with regard to a single diagnostic marker indicating periprosthetic joint infection (PJI) with sufficient sensitivity and specificity is still missing. The immunologically reactive molecule Pecam-1 is shed from the T-cell surface upon activation via proinflammatory signaling, e.g., triggered by specific pathogens. We hypothesized that soluble Pecam-1 (sPecam-1) can hence function as a biomarker of PJI. Fifty-eight patients were prospectively enrolled and assigned to one of the respective treatment groups (native knees prior to surgery, aseptic, and septic total knee arthroplasty (TKA) revision surgeries). Via synovial sample acquisition and ELISA testing, a database on local sPecam-1 levels was established. We observed a significantly larger quantity of sPecam-1 in septic (n = 22) compared to aseptic TKA revision surgeries (n = 20, p ≤ 0.001). Furthermore, a significantly larger amount of sPecam-1 was found in septic and aseptic revisions compared to native joints (n = 16, p ≤ 0.001). Benchmarking it to the gold standard showed a high predictive power for the detection of PJI. Local sPecam-1 levels correlated to the infection status of the implant, and thus bear a strong potential to act as a biomarker of PJI. While a clear role of sPecam-1 in infection could be demonstrated, the underlying mechanism of the molecule’s natural function needs to be further unraveled.

Noninvasive diagnostic of periprosthetic joint infection by urinary peptide markers: A preliminary study

Previous immunohistochemical analyses revealed altered protein expression in the periprosthetic membranes of patients with periprosthetic joint infection (PJI). Proteins are degraded to peptides that may pass the blood-kidney barrier depending on their size. The aim of this study was to evaluate if PJI can be diagnosed based on the urinary peptide excretion pattern. Thirty patients undergoing removal of their hip or knee prostheses due to septic or aseptic loosening were enrolled. Specimen sampling was performed according to the MusculoSkeletal Infection Society criteria. A urinary sample was analyzed before surgery using capillary electrophoresis coupled with mass spectrometry. Peptides with differential urinary excretion between groups were used to establish a multimarker model. A total of 137 peptides were differentially excreted between the septic and aseptic groups. The majority of identified peptide markers were fragments of structural extracellular matrix proteins, potentially due to their origin from the periprosthetic membrane. A marker model with 83 peptides achieved the best diagnostic performance for diagnosing PJI with a sensitivity of 95%, a specificity of 90%, and an area under the curve of 0.96. The altered protein expression pattern in the periprosthetic membrane of PJI is most likely reflected in excreted urinary peptides. Thus, the diagnosis of PJI by urinary peptide markers seems to be a reasonable approach.

Current Clinical Methods for Detection of Peri-Prosthetic Joint Infection

Background: Currently, one of the most pressing problems in the field of orthopedic surgery is peri-prosthetic joint infection [PJI]. While there are numerous ways to detect PJI, current clinical detection methods differ across institutions and have varying criteria and protocols. Some of these methods include the Modified Musculoskeletal Infection Society system, culturing, polymerase chain reaction, the determination of the presence of certain biomarkers, testing for the presence of alpha defensin peptides, and leukocyte level testing. Methods: This review summarizes the most recent publications in the field of PJI detection to highlight current strengths as well as provide future directions to find the system for the quickest, cost-effective, and most accurate way to diagnose these types of infections. Results: The results of this literature review suggest that, while each method of diagnosis has its advantages, each has various drawbacks as well. Current methods can be expensive, take days to weeks to complete, be prone to contamination, and can produce ambiguous results. Conclusions: The findings in this review emphasize the need for a more comprehensive and accurate system for diagnosing PJI. In addition, the specific comparison of advantages and drawbacks can be useful for researchers and clinicians with goals of creating new diagnostic tests for PJIs, as well as in clinical scenarios to determine the correct treatment for patients.

How reliable is the next generation of multiplex-PCR for diagnosing prosthetic joint infection compared to the MSIS criteria? Still missing the ideal test

INTRODUCTION

Identification of the pathogen in case of a periprosthetic joint infection (PJI) remains 1 of the greatest challenges in septic surgery. Rapid germ identification enables timely, specific, antimicrobial therapy. The first multiplex PCR (polymerase chain reaction) generation (Unyvero-i60) enables germ detection within 5 hours with a sensitivity of 78.8% and a specificity of 100%. The aim of this study is to investigate the performance of the new generation of cartridges (Unyvero-ITI) of multiplex PCR in the case of a PJI.

METHODS

In a prospective study, intraoperatively aspirated synovial fluid from 97 patients with aseptic or septic hip or knee revision surgery (49 aseptic, 48 septic) was examined with the multiplex PCR system (Unyvero-ITI) and the results were compared with the MSIS criteria. In addition, the time until the microbiological result was obtained in the event of a germ detection was documented.

RESULTS

The multiplex PCR showed a germ detection with a sensitivity of 85.1% and a specificity of 98.0%. In 7 cases a false negative result was found and in one patient a false positive result was found. The general accuracy of this test procedure was 91.8%. The detection of germs was carried out within 5 hours with the multiplex PCR compared to 4.9 days in conventional microbiological diagnostics.

CONCLUSIONS

The new generation of multiplex-PCR was able to improve germ detection. The possibility of prompt detection of germs offers the option of faster, targeted antimicrobial therapy. This diagnostic tool offers significant advantages, particularly in the context of an acute periprosthetic infection.

The 2018 International Consensus Meeting Minor Criteria for Chronic Hip and Knee Periprosthetic Joint Infection: Validation From a Single Center

BACKGROUND

Recently, a revised definition of the minor criteria scoring system for diagnosing periprosthetic joint infection (PJI) was developed by the second International Consensus Meeting on musculoskeletal infection. The new system combines preoperative and intraoperative findings, reportedly achieving high sensitivity and specificity. We aimed to validate the modified scoring system at a high-volume center.

METHODS

We retrospectively reviewed patients who underwent a revision total hip or knee arthroplasty at our institution from May 2015 to August 2018. Serum C-reactive protein, synovial white blood cell count and polymorphonuclear percentage, leukocyte esterase test, alpha-defensin, microbiological and histologic results, and documented existence of sinus tract and intraoperative purulence were available for all patients. Cases with at least 1 major criterion were considered as infected. Using the new minor criteria, a score of ≥6 reflects PJI, while a score <3 can be considered as noninfected. Sensitivity, specificity, mean accuracy (ACC), positive predictive value (PPV), and negative predictive value (NPV) were analyzed.

RESULTS

A total of 345 cases were included. A cutoff score of ≥6 points had the following diagnostic performance: area under the curve (AUC) = 0.90; ACC = 0.88; sensitivity = 0.96; specificity = 0.84; PPV = 0.70; NPV = 0.98. Diagnostic performance was better for the hip (AUC = 0.92; ACC = 0.90; sensitivity = 0.96; specificity = 0.86; PPV = 0.81; NPV = 0.98) than the knee (AUC = 0.89; ACC = 0.85; sensitivity = 0.95; specificity = 0.83; PPV = 0.59; NPV = 0.98).

CONCLUSION

The modified scoring system proposed by the 2018 International Consensus Meeting in diagnosing PJI showed high sensitivity and a good performance, especially as rule-out diagnostic criteria. The cutoff level seems to be different between the hip and knee. Further validation studies considering the acknowledged limitations are recommended.

Reporting Outcomes of Treatment for Periprosthetic Joint Infection of the Knee and Hip Together With a Minimum 1-Year Follow-Up is Reliable

BACKGROUND

Although there is an increasing trend toward reporting the outcome of hip and knee arthroplasty separately, it remains unknown whether joint-specific reporting is necessary for periprosthetic joint infection (PJI) as sample sizes are already low, given its relatively rare occurrence. The aim of this study is to compare treatment outcomes of PJI occurring after knee and hip arthroplasty. Furthermore, we aim to establish the necessary follow-up time for an accurate reporting of PJI treatment outcomes.

METHODS

A retrospective study of 792 cases of hip and knee PJI treated with irrigation and debridement or two-stage exchange arthroplasty from 2000 to 2017 was performed. Treatment failure was defined based on the Delphi method-based criteria. The Kaplan-Meier survivorship curves were generated, and a log-rank test was used to evaluate differences in survivorship. A multivariate Cox proportional hazards regression and a sensitivity analysis using propensity matching were performed. A two-piecewise linear regression model was used to examine the threshold effect of time after treatment on survival rates.

RESULTS

There were no significant differences between hip and knee PJIs in overall survivorship (P = .71), or when stratified by irrigation and debridement (P = .39), or two-stage exchange arthroplasty (P = .59). There was also no difference by joint in the multivariate or sensitivity analysis. Survival rates had the most dramatic rates of decrease in the initial months after treatment of PJI but began to plateau after 1.09 years.

CONCLUSION

This study reveals no difference in treatment outcomes between knee and hip PJIs. In addition, given the difficulty with obtaining follow-up, we suggest that one-year follow-up is sufficient for an accurate reporting of treatment failure.

False-Positive Automated Synovial Fluid White Blood Cell Counting Is a Concern for Both Hip and Knee Arthroplasty Aspirates

BACKGROUND

Although false elevation of automated leukocyte (white blood cell [WBC]) counts has been described in the setting of hip corrosion, the more general correlation between manual and automated cell counts among synovial fluid aspirates from hip and knee arthroplasties has not been studied.

METHODS

This retrospective review at one laboratory identified 8607 consecutive synovial fluid samples from arthroplasties and 812 from native knees, each with an automated WBC count > 3000 cells/μL and a corresponding paired reflex manual count. The correlation between automated and manual counts was evaluated, as was the rate of false-positive automated WBC counts.

RESULTS

The correlation between automated WBC counts for native knees, total knee arthroplasties, and total hip arthroplasties was near-perfect, strong, and moderate, respectively. The false-positive rates for automated counts were 4.4%, 10.1%, and 34.3%, respectively (P < .0001). International Consensus Meeting scores and culture positivity demonstrated that manual counts, not automated counts, were correct.

CONCLUSION

The presence of a hip or knee arthroplasty appears to substantially increase the risk of a false-positive automated synovial fluid WBC count. Clinicians evaluating an arthroplasty should exercise caution when interpreting positive automated WBC counts, and consider requesting a reflex manual count, to verify the accuracy of automated cell counting.

Diagnosis and management of implant debris-associated inflammation

Introduction: Total joint replacement is one of the most common, safe, and efficacious operations in all of surgery. However, one major long-standing and unresolved issue is the adverse biological reaction to byproducts of wear from the bearing surfaces and modular articulations. These inflammatory reactions are mediated by the innate and adaptive immune systems.Areas covered: We review the etiology and pathophysiology of implant debris-associated inflammation, the clinical presentation and detailed work-up of these cases, and the principles and outcomes of non-operative and operative management. Furthermore, we suggest future strategies for prevention and novel treatments of implant-related adverse biological reactions.Expert opinion: The generation of byproducts from joint replacements is inevitable, due to repetitive loading of the implants. A clear understanding of the relevant biological principles, clinical presentations, investigative measures and treatments for implant-associated inflammatory reactions and periprosthetic osteolysis will help identify and treat patients with this issue earlier and more effectively. Although progressive implant-associated osteolysis is currently a condition that is treated surgically, with further research, it is hoped that non-operative biological interventions could prolong the lifetime of joint replacements that are otherwise functional and still salvageable.

Twenty common errors in the diagnosis and treatment of periprosthetic joint infection

Background

Misconceptions and errors in the management of periprosthetic joint infection (PJI) can compromise the treatment success. The goal of this paper is to systematically describe twenty common mistakes in the diagnosis and management of PJI, to help surgeons avoid these pitfalls.

Materials and methods

Common diagnostic and treatment errors are described, analyzed and interpreted.

Results

Diagnostic errors include the use of serum inflammatory biomarkers (such as C-reactive protein) to rule out PJI, incomplete evaluation of joint aspirate, and suboptimal microbiological procedures (such as using swabs or collection of insufficient number of periprosthetic samples). Further errors are missing possible sources of distant infection in hematogenous PJI or overreliance on suboptimal diagnostic criteria which can hinder or delay the diagnosis of PJI or mislabel infections as aseptic failure. Insufficient surgical treatment or inadequate antibiotic treatment are further reasons for treatment failure and emergence of antimicrobial resistance. Finally, wrong surgical indication, both underdebridement and overdebridement or failure to individualize treatment can jeopardize surgical results.

Conclusion

Multidisciplinary teamwork with infectious disease specialists and microbiologists in collaboration with orthopedic surgeons have a synergistic effect on the management of PJI. An awareness of the possible pitfalls can improve diagnosis and treatment results.

Factors to Consider When Assessing the Diagnostic Accuracy of Synovial Leukocyte Count in Periprosthetic Joint Infection

Synovial white blood cell (WBC) count and the percentage of polymorphonuclear leucocytes (PMN%) is one of the diagnostic criteria to diagnose a periprosthetic joint infection (PJI). Although the test is widely available, the diagnostic accuracy of proposed cut-off levels are influenced by several factors, such as: the affected joint, co-morbid conditions, the causative microorganism and the gathering and processing of samples in the laboratory. In this narrative review we provide an overview on how and to what extent these factors can affect the synovial WBC count and PMN% in synovial fluid.

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.