Synovial Biomarkers to Detect Chronic Periprosthetic Joint Infection: A Pilot Study to Compare Calprotectin Rapid Test, Calprotectin ELISA Immunoassay and Leukocyte Esterase Test

Synovial fluid viscosity with synovial fluid cell count, valuable diagnostic marker of prosthetic joint infections

In the absence of standard criteria for prosthetic joint infections (PJI), several diagnostic modalities have been proposed mostly concentrating on novel biochemical markers. The physical chemistry markers received scarce attention. Synovial fluid (SF) viscosity could be considered as marker for PJI, however, its diagnostic value of PJI remains unknown. Our study aimed to determine the potential of SF viscosity as a diagnostic marker of PJI and compare it to SF cell count with differential (CCD). We prospectively analysed 123 SF samples (58 septic and 65 aseptic) for viscosity and CCD of SF obtained during hip and knee revision procedures. The diagnosis of PJI based on EBJIS criteria. The viscosity cut-off for PJI was calculated and the diagnostic power was compared to CCD. The mean SF viscosity in the PJI group was 8.5 ± 0.4 mPa s and 103.2 ± 18.8 mPa s in the aseptic group (p < 0.05). SF viscosity achieved 100% sensitivity and 85.3% specificity, with AUC 0.832 (95% CI 0.739, 0.925). Combination of SF viscosity and CCD achieved AUC 0.951 (95% CI 0.919, 0.987). SF viscosity is more sensitive but slightly less specific in diagnosing PJI than SF CCD. Best diagnostic value is achieved combining SF viscosity with CCD in detection of PJI.

Analytical and clinical considerations of synovial fluid calprotectin in diagnosing periprosthetic joint infections

Calprotectin is a protein predominantly found in the cytosol of myeloid cells, such as neutrophils and monocytes. Calprotectin has several functions in innate immunity, such as attenuating bacteria, recruiting and activating immune cells, and aiding in the production of pro-inflammatory cytokines and reactive oxygen species. Due to its presence in inflammatory sites, it has been investigated as a biomarker for various medical conditions, especially Inflammatory bowel diseases (IBD), rheumatoid arthritis (RA), and has gained interest in the diagnosis of several infectious diseases, in particular for diagnosing periprosthetic joint infections (PJI). Synovial fluid calprotectin has demonstrated to be a sensitive and specific biomarker for both confirming as well as excluding PJI. Synovial fluid calprotectin can be measured using enzyme-linked immunosorbent assay (ELISA), immunoturbidimetry, and lateral flow methods. It is a generally stable biomarker, showing no significant decrease or increase in its levels despite blood or lipid contamination, storage duration, freeze-thaw cycles, and enzymatic pretreatments for viscosity reduction. This review discusses the biology and physiology of calprotectin, pathophysiology of PJI, and the clinical and analytical considerations surrounding its use in diagnosing PJI.

The Application of artificial intelligence in periprosthetic joint infection

Periprosthetic joint infection (PJI) represents one of the most devastating complications following total joint arthroplasty, often necessitating additional surgeries and antimicrobial therapy, and potentially leading to disability. This significantly increases the burden on both patients and the healthcare system. Given the considerable suffering caused by PJI, its prevention and treatment have long been focal points of concern. However, challenges remain in accurately assessing individual risk, preventing the infection, improving diagnostic methods, and enhancing treatment outcomes. The development and application of artificial intelligence (AI) technologies have introduced new, more efficient possibilities for the management of many diseases. In this article, we review the applications of AI in the prevention, diagnosis, and treatment of PJI, and explore how AI methodologies might achieve individualized risk prediction, improve diagnostic algorithms through biomarkers and pathology, and enhance the efficacy of antimicrobial and surgical treatments. We hope that through multimodal AI applications, intelligent management of PJI can be realized in the future.

Rapid multiplex micro-ELISA assay for simultaneous measurement of synovial biomarkers : a potential aid in diagnosing periprosthetic joint infection?

Aims

The diagnosis of periprosthetic joint infection (PJI) remains a challenge, as no single diagnostic test shows high diagnostic accuracy. Recently, the measurement of synovial biomarkers has shown promising results. The aim of this study was to present a novel multiplex micro-enzyme-linked immunosorbent assay (ELISA) method for the rapid and simultaneous measurement of alpha-defensin, interleukin (IL)-6, and calprotectin developed in a model buffer system and human spiked synovial fluid.

Methods

A microfluidics- and chemiluminescence-based multiplex micro-ELISA point-of-care testing system was employed for the rapid and simultaneous measurement of alpha-defensin, calprotectin, and IL-6 developed in a model buffer system and spiked human synovial fluid. Cut-off values of 1.56 µg/ml for alpha-defensin, 50 µg/ml for calprotectin, and 0.031 µg/ml for IL-6 were extracted from the literature as optimal cut-off values for the diagnosis of PJI, and were used for comparison.

Results

Limit of detection (LoD) was determined for each individual biomarker by means of calibration curves with serial dilutions in a model buffer system. LoDs of 0.008, 0.002, and 0.00014 µg/ml were determined for alpha-defensin, calprotectin, and IL-6, respectively. The spiked synovial fluid assay determined LoDs of 0.08, 0.31, and 0.004 µg/ml for alpha-defensin, calprotectin, and IL-6, respectively.

Conclusion

These findings highlight the proposed platform's unique features, including simultaneous measurement of three key synovial biomarkers, minimal sample volume requirements (5 to 50 µl), lower LoDs compared to conventional tests, and a short processing turnaround time of 22 minutes. Further validation studies are necessary to confirm its clinical utility.

Periprosthetic joint infections: state-of-the-art

In general, periprosthetic joint infection (PJI) is regarded as one of the most common complications of total joint arthroplasty (TJA) and may lead to surgical failure, revision surgery, amputation or death. Nowadays, PJI has become a global health concern, which brings a great burden to public healthcare. In addition, there are still obstacles to achieve high success rates in the prevention, diagnosis and treatment of PJI. However, promising studies are also available with the advancements in biotechnology. This article will present an overview of the current methods used in the prevention, diagnosis and management of PJI while underlining the new technologies utilized.

Synovial calprotectin in prosthetic joint infection. A systematic review and meta-analysis of the literature

INTRODUCTION

Calprotectin is a protein endowed with antimicrobial properties, rendering it a distinctive marker for infection. Two methods are currently available for the assay of calprotectin: the enzyme-linked immunosorbent assay (ELISA) and the lateral flow test (LFT). We aimed to assess the diagnostic accuracy of synovial fluid calprotectin and to compare the accuracy of the laboratory-based test and the qualitative assessment for the diagnosis of hip and knee prosthetic infection.

MATERIALS AND METHODS

We searched (from inception to November 2023) MEDLINE, Scopus, EMBASE, Web of Science, and Cochrane for studies on calprotectin in the diagnosis of periprosthetic joint infection (PJI). Sensitivity, specificity, positive and negative likelihood ratio (LR), and diagnostic odds ratio were analyzed. The receiver-operating curve for each method was calculated.

RESULTS

We included 14 articles in our meta-analysis, including 902 patients who underwent total hip and knee arthroplasties revision; 331 (37%) had a joint infection according to MSIS, MSIS-modified criteria, ICM 2018 and EBJIS 2021. Considering the false-positive result rate of 6% and false-negative result rate of 7%, pooled sensitivity and specificity were 0.92 (95% CI 0.89-0.94) and 0.93 (0.91-0.95), respectively. The area under the curve (AUC) was 0.93 (95% CI 0.91-0.94). No statistical differences in terms of sensitivity and specificity were found between ELISA and LFT. The pooled sensitivity and specificity of the two calprotectin assessment methods were: LFT 0.90 (95% CI 0.869-0.935) and 0.92 (95% CI 0.894-0.941), respectively; ELISA 0.96 (95% CI 0.914-0.986) and 0.97 (95% CI 0.934-0.988), respectively. The diagnostic odds ratio of the ELISA was superior to that of the LFT (906.6667, 95% CI 271.2686-3030.3712 versus 113.8886, 95% CI 70.4001-184.2414; p < 0.001). The AUC for ELISA and LFT was 0.968 (95% CI 0.944-0.984) and 0.915 (95% CI 0.895-0.933), respectively.

CONCLUSIONS

Detection of synovial calprotectin is an accurate test for diagnosis of hip and knee prosthetic infections. The diagnostic accuracy of the two calprotectin assessment methods is almost comparable. The LFT is a valid, rapid, and more available diagnostic tool, particularly to rule out PJI.

Comparative performance analysis of Synovasure™ and Leukocyte Esterase assays for the diagnosis of periprosthetic infections in complex microbiological situations

INTRODUCTION

Osteoarticular infections (OAI) after prosthetic surgery have serious functional and economic consequences. Rapid tests for alpha-defensin (TAD) and leukocyte esterase (TLE) are two intra-articular markers involved in the diagnosis of OAIs. TLE cannot be applied in the presence of blood unless centrifugation is used, but the rate of "non-application" of the test for this reason is unknown in complex microbiological situations (discordant or negative puncture, ongoing antibiotic treatment). We therefore conducted a prospective study to determine: 1) the performance of the TAD and TLE rapid tests in diagnosing complex OAI, 2) the rate of non-application of the TLE due to hemarthrosis, and 3) the concordance between the two tests.

ASSUMPTION

These two diagnostic tests had a negative predictive value (NPV) ≥ 90% for the diagnosis of complex OAI.

MATERIALS AND METHODS

A total of 79 suspected OAI patients with complex microbiological diagnoses were included between 2018 and 2023. They were 52 men (66%) for 27 women (34%), with a mean age of 66 ± 13.5 years. The hip (n = 41, 52%) and knee (n = 36, 46%) were the most represented, followed by the elbow (n = 1, 1%) and shoulder (n = 1, 1%). These patients were suspected of having an OAI that required joint puncture, but with a complex microbiological diagnosis due to discordant punctures (n = 21, 27%) or sterile punctures despite strong suspicion of infection (n = 50, 63%), or in case of ongoing antibiotic treatment (n = 8, 10%). All patients underwent joint fluid puncture followed by TAD (Synovasure™, Zimmer, Warsaw, IN, USA) and, when the macroscopic appearance of the sample allowed (clear fluid group), TLE (Multistix 8SG, Siemens Healthcare GmbH, Erlangen, Germany). The results of both tests were compared with Musculoskeletal Infection Society (MSIS) criteria.

RESULTS

Of the 79 patients included, 27 (34%) were considered infected according to the MSIS. In 30% of cases (n = 24), TLE was not feasible due to the presence of blood in the joint fluid. In the "clear fluid" group, the NPV was equal to 90% for both TAD (sensitivity 87%, specificity 88%) and TLE (sensitivity 87%, specificity 81%). The two parameters showed almost perfect agreement (κ = 0.927).

CONCLUSION

TAD and TLE are two rapid, reliable tests with near-perfect concordance and high NPV, even in situations of complex microbiological diagnosis. They are particularly useful for deciding on a therapeutic strategy for patients with complex OAI. The TLE cannot be used in 30% of cases due to hemarthrosis, but centrifugation can correct this defect.

LEVEL OF EVIDENCE

III; Prospective comparative diagnostic accuracy study.

Active myeloperoxidase: a promising biomarker to differentiate "acute" and "low-grade" peri-prosthetic joint infections from aseptic failures

Introduction

The accurate distinction between periprosthetic joint infections (PJI) and aseptic failures (AF) is of paramount importance due to differences in treatment. However, this could be challenging by using the current criteria. Various synovial fluid biomarkers are being assessed to improve the diagnostic accuracy. Myeloperoxidase (MPO), an enzyme contained in the granules of neutrophils, may be a promising biomarker for PJI.

Methods

Synovial fluids of 99 patients (n = 65 PJI according to EBJIS criteria; n = 34 AF) were collected in two specialized orthopedic centers. PJI were divided into acute (n = 33) and low-grade (n = 32) according to previously published classification. An activity assay specific for active MPO was performed in each sample. Ability of MPO to correctly discriminate patients with PJI from AF was determined by ROC analysis. The best discriminating cut-off value was determined by calculating the J Youden index. For all analyses, a P value < 0.05 was considered statistically significant.

Results

Active MPO was higher in PJI than AF (P < 0.0001). The ROC analysis revealed a significant area under the curve (AUC: 0.86; 95% CI: 0.78-0.93, P < 0.0001). A cut-off value of 561.9 U/mL, with good sensitivity (0.69) and specificity (0.88), discriminated between AF and PJI (accuracy 75.76%, 95% CI: 66.11-83.81%, positive likelihood ratio 5.88, 95% CI: 2.31-14.98 and negative likelihood ratio 0.35, 95%CI: 0.24-0.51). No difference in MPO levels was found between acute and chronic low-grade PJI.

Conclusion

The proposed assay appears to be a reliable and affordable tool for detecting the active MPO in synovial fluid, with promising characteristics of sensitivity and specificity in discriminating both acute and low-grade PJI from AF. Further studies are needed to confirm MPO diagnostic cut-off values and validate their use in the routine clinical practice.

Differences in the Synovial Fluid Proteome of Septic and Aseptic Implant Failure

Implant loosening is a severe complication after total joint replacement. Here, differential diagnosis between septic and aseptic cases is crucial for further surgical treatment, but low-grade periprosthetic joint infections (PJIs) in particular remain a challenge. In this study, we analyzed the synovial fluid proteome of 21 patients undergoing revision surgery for septic (eight cases) or aseptic (thirteen cases) implant failure using LC-MS/MS to identify potential new biomarkers as future diagnostic tools. Staphylococci were found in four cases, Streptococci in two cases, Serratia marcescens and Cutibacterium acnes in one case. Proteomic analysis of the synovial fluid resulted in the identification of 515 different proteins based on at least two peptides. A statistical comparison revealed 37 differentially abundant proteins (p < 0.05), of which 17 proteins (46%) showed a higher abundance in the septic group. The proteins with the highest fold change included the known marker proteins c-reactive protein (7.57-fold) and the calprotectin components protein S100-A8 (4.41-fold) and protein S100-A9 (3.1-fold). However, the protein with the highest fold change was leucine-rich alpha-2-glycoprotein 1 (LRG1) (9.07-fold), a currently discussed new biomarker for inflammatory diseases. Elevated LRG1 levels could facilitate the diagnosis of PJI in the future, but their significance needs to be further investigated.

Early Biofilm Formation on the Drain Tip after Total Knee Arthroplasty Is Not Associated with Prosthetic Joint Infection: A Pilot Prospective Case Series Study of a Single Center

BACKGROUND

Periprosthetic joint infection (PJI) is a devastating complication of arthroplasties that could occur during the surgery. The purpose of this study was to analyze the biofilm formation through microbiological culture tests and scanning electron microscopy (SEM) on the tip of surgical drainage removed 24 h after arthroplasty surgery.

METHODS

A total of 50 consecutive patients were included in the present prospective observational study. Drains were removed under total aseptic conditions twenty-four hours after surgery. The drain tip was cut in three equal parts of approximately 2-3 cm in length and sent for culture, culture after sonication, and SEM analysis. The degree of biofilm formation was determined using a SEM semi-quantitative scale.

RESULTS

From the microbiological analysis, the cultures of four samples were positive. The semi-quantitative SEM analysis showed that no patient had grade 4 of biofilm formation. A total of 8 patients (16%) had grade 3, and 14 patients (28%) had grade 2. Grade 1, scattered cocci with immature biofilm, was contemplated in 16 patients (32%). Finally, 12 patients (24%) had grade 0 with a total absence of bacteria. During the follow-up (up to 36 months), no patient showed short- or long-term infectious complications.

CONCLUSIONS

Most of the patients who underwent primary total knee arthroplasty (TKA) showed biofilm formation on the tip of surgical drain 24 h after surgery even though none showed a mature biofilm formation (grade 4). Furthermore, 8% of patients were characterized by a positivity of culture analysis. However, none of the patients included in the study showed signs of PJI up to 3 years of follow-up.

Synovial Fluid Biomarkers for the Diagnosis of Periprosthetic Joint Infection-A Systematic Review and Meta-Analysis of Their Diagnostic Accuracy According to Different Definitions

BACKGROUND

Different synovial fluid biomarkers have emerged to improve periprosthetic joint infection (PJI) diagnosis. The goals of this paper were (i) to assess their diagnostic accuracy and (ii) to evaluate their performance according to different PJI definitions.

METHODS

A systematic review and meta-analysis was performed using studies that reported diagnostic accuracy of synovial fluid biomarkers using validated PJI definitions published from 2010 to March 2022. A database search was performed through PubMed, Ovid MEDLINE, Central, and Embase. The search identified 43 different biomarkers with four being the more commonly studied, with 75 papers overall: alpha-defensin; leukocyte esterase; synovial fluid C-reactive protein; and calprotectin.

RESULTS

Overall accuracy was higher for calprotectin, followed by alpha-defensin, leukocyte esterase, and synovial fluid C-reactive protein with sensitivities of 78 to 92% and specificities of 90 to 95%. Their diagnostic performance was different according to which definition was adopted as the reference. Specificity was consistently high across definitions for all four biomarkers. Sensitivity varied the most with lower values for the more sensitive European Bone and Joint Infection Society or Infectious Diseases Society of America definitions with higher values for the Musculoskeletal Infection Society definition. The International Consensus Meeting 2018 definition showed intermediate values.

CONCLUSION

All evaluated biomarkers had good specificity and sensitivity, making their use acceptable in the diagnosis of PJI. Biomarkers perform differently according to the selected PJI definitions.

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.

Novel diagnostic markers for periprosthetic joint infection: a systematic review

Background

Identifying novel biomarkers that are both specific and sensitive to periprosthetic joint infection (PJI) has the potential to improve diagnostic accuracy and ultimately enhance patient outcomes. Therefore, the aim of this systematic review is to identify and evaluate the effectiveness of novel biomarkers for the diagnosis of PJI.

Methods

We searched the MEDLINE, EMBASE, PubMed, and Cochrane Library databases from January 1, 2018, to September 30, 2022, using the search terms "periprosthetic joint infection," "prosthetic joint infection," or "periprosthetic infection" as the diagnosis of interest and the target index, combined with the term "marker." We excluded articles that mentioned established biomarkers such as CRP, ESR, Interleukin 6, Alpha defensin, PCT (procalcitonin), and LC (leucocyte cell count). We used the MSIS, ICM, or EBJS criteria for PJI as the reference standard during quality assessment.

Results

We collected 19 studies that analyzed fourteen different novel biomarkers. Proteins were the most commonly analyzed biomarkers (nine studies), followed by molecules (three studies), exosomes (two studies), DNA (two studies), interleukins (one study), and lysosomes (one study). Calprotectin was a frequently analyzed and promising marker. In the scenario where the threshold was set at ≥50-mg/mL, the calprotectin point-of-care (POC) performance showed a high sensitivity of 98.1% and a specificity of 95.7%.

Conclusion

None of the analyzed biomarkers demonstrated outstanding performance compared to the established parameters used for standardized treatment based on established PJI definitions. Further studies are needed to determine the benefit and usefulness of implementing new biomarkers in diagnostic PJI settings.

Antibiotic Prophylaxis in One-Stage Revision of Septic Total Knee Arthroplasty: A Scoping Review

BACKGROUND

Total knee replacement (TKA) is becoming a routine procedure in orthopedic surgery. One of the possible complications of this surgery is periprosthetic joint infection (PJI). The purpose of this study is to identify, through a literature review, which antibiotic is used as prophylaxis for septic one-stage revision TKA and what is the rationale for its use.

METHODS

We searched: MEDLINE, Embase, PsycINFO on Ovid, the Cochrane Library, and the Google Scholar Database. The searches were limited by date (January 2005 to September 2022) and to the English language. All types of original research were considered, including prospective or retrospective longitudinal studies, cross-sectional studies, and randomized trials. The specific search terms were ((antibiotic [MeSH]) AND (prophylaxis)) and (TKA OR TKR OR "Arthroplasty, Replacement, Knee" [MeSH] OR ((knee) adj2 (replace* OR arthroplasty* OR prosthe*))).

RESULTS

Despite our research efforts, we found no article capable of answering the question of which antibiotic to use as surgical prophylaxis for a septic revision one-stage TKA.

CONCLUSIONS

Although the research results are inconclusive, we would recommend using the same antibiotic prophylaxis as for primary joint replacement, i.e., cefazolin, as it was recommended for its low side effect rate and relative effectiveness.

The Challenge of Periprosthetic Joint Infection Diagnosis: From Current Methods to Emerging Biomarkers

Due to the increase in the life span and mobility at older ages, the number of implanted prosthetic joints is constantly increasing. However, the number of periprosthetic joint infections (PJIs), one of the most severe complications after total joint arthroplasty, also shows an increasing trend. PJI has an incidence of 1-2% in the case of primary arthroplasties and up to 4% in the case of revision operations. The development of efficient protocols for managing periprosthetic infections can lead to the establishment of preventive measures and effective diagnostic methods based on the results obtained after the laboratory tests. In this review, we will briefly present the current methods used in PJI diagnosis and the current and emerging synovial biomarkers used for the prognosis, prophylaxis, and early diagnosis of periprosthetic infections. We will discuss treatment failure that may result from patient factors, microbiological factors, or factors related to errors during diagnosis.

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.

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.

What's New in the Diagnosis of Periprosthetic Joint Infections: Focus on Synovial Fluid Biomarkers

Periprosthetic joint infections are some of the leading causes of revision prosthetic surgery, accounting for 25% of failed total knee replacements and 15% of failed total hip replacements. The search for a biomarker that, together with clinical and radiological findings, could improve the management of such patients is currently a significant challenge for orthopaedic surgeons. Synovial fluid is a viscous and mucinous substance produced by the synovium, a specialized connective tissue that lines diarthrodial joints. Synovial fluid is an ultrafiltrate of plasma but also contains proteins secreted from the surrounding tissues, including the articular cartilage and synovium. Therefore, synovial fluid represents a source of disease-related proteins that could be used as potential biomarkers in several articular diseases. Based on these findings, the study of synovial fluid has been gaining increasing importance in recent years. This review aims to assess the accuracy and the limitations of the most promising synovial fluid biomarkers-i.e., Alpha-Defensin, Leukocyte Esterase, C-Reactive Protein, Interleukin-6, Calprotectin, Presepsin and Neopterin-in the diagnosis of PJI. Special attention will be given to emerging synovial biomarkers, which could soon be important in diagnosing PJIs.

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.

The role of antibiotic calcium sulfate beads in acute periprosthetic knee infection: a retrospective cohort study

Background

The study aimed to compare debridement, antibiotics, and implant retention (DAIR) vs. debridement antibiotic bead and retention of the implant (DABRI) in terms of infection-free success rate and treatment cost for acute periprosthetic joint infections after total knee arthroplasty (TKA).

Method

Between 2017 and 2020, 32 patients with acute periprosthetic joint infection who were treated by total knee arthroplasty were retrospectively reviewed. The patients were divided into a DAIR group (n=15) and a DABRI group (n=17). During the DABRI, additional calcium ulphate antibiotic beads were used. Patient age, the Musculoskeletal Infection Society score, microorganisms involved, and success rate were assessed.

Results

The mean age of DAIR group (n=15) was 69 years, with 7 being male, and 8 female. The mean follow-up period lasted 30 months. The success rate was 80% (12/15). The mean age of DABRI group (n=17) was 64 years, with 10 patients being male and 7 female. The mean follow-up period was 16 months. The success rate was 88% (15/17). There were no significant differences in patient age (P>0.05), the Musculoskeletal Infection Society score (P>0.05), and success rate (P>0.05). A significant difference was found in the follow-up period between the two groups (P<0.05).

Conclusion

Both DAIR and DABRI could be used to treat acute periprosthetic joint infections and the outcomes and treatment costs of the two procedures were comparable. Additional use of calcium sulfate beads was safe, but might not improve the treatment result. Randomized controlled studies are warranted for the routine use.

Synovial fluid calprotectin in diagnosing periprosthetic joint infection: A meta-analysis

Purpose

Periprosthetic joint infection (PJI) is one of the most debilitating complications following joint replacement surgery. Synovial biomarkers, such as Calprotectin, have become valuable in the diagnosis of PJI. This meta-analysis aimed to investigate the role of synovial Calprotectin as a diagnostic test in PJI.

Methods

This meta-analysis was conducted with adherence to PRISMA guidelines. PubMed, Cochrane, Web of Science, and Google Scholar were searched until February 2022. Inclusion criteria were as follows: all studies in which the patients with joint replacements were evaluated for PJI; synovial Calprotectin was the biomarker of choice to diagnose PJI; standardized guidelines were used as the gold standard for the diagnosis; and a comparison between the guidelines and Calprotectin results was made. Diagnostic parameters such as sensitivity, specificity, diagnostic odds ratio (DOR), positive predictive value, negative predictive value, and area under the curve (AUC) were calculated for the included studies to evaluate synovial Calprotectin for PJI diagnosis.

Results

The total number of the included patients was 618 from eight studies. The pooled sensitivity, specificity, and diagnostic odds ratio of Calprotectin test were 92% (95%CI: 84%-98%), 93% (95%CI: 84%-99%), and 187.61 (95%CI: 20.21–1741.18), respectively. The results showed that the negative and positive likelihood ratios of the Calprotectin test were 0.07 (95%CI: 0.02–0.22) and 9.91 (95%CI: 4.11–23.93), respectively. The SROC showed that the area under the curve for Calprotectin test was 0.935.

Conclusion

Synovial Calprotectin is a valuable biomarker as it provides a reliable and rapid diagnosis of PJI. It has the potential to be used in clinical practice due to its high sensitivity and specificity that are comparable to the other utilized biomarkers. Another advantage is its low cost relative to other biomarkers.