Does inflammatory joint diseases affect the accuracy of infection biomarkers in patients with periprosthetic joint infections? A prospective comparative reliability study

Periprosthetic joint infections in patients with rheumatoid arthritis are associated with higher complication and mortality rates

INTRODUCTION

Periprosthetic joint infection (PJI) remains the most devasting complication after total joint arthroplasty (TJA). There has been a significant focus on this topic in recently-published medical literature. However, relatively little has been published about PJI in patients with rheumatoid arthritis (RA), which are often physiologically frail and immunocompromised. A better understanding of PJI in this patient population is therefore crucial. The main aims of this paper are to (1) report complication and mortality rates in a cohort of PJI-RA patients; and (2) clinically characterize them.

METHODS

Medical and surgical records of all RA PJI patients treated surgically from 2003 to 2020 were retrospectively reviewed. Medical history, physical examination, reactive protein (CRP) level, procalcitonin, white blood cell (WBC) count, joint aspiration results, and cultures were used to determine PJI.

RESULTS

54PJIs, 49 of them chronic, were treated in 53RA patients. Mean patient age was 65 yrs. (range = 32-88); 33females and 20 males (one bilateral hip). The overall mortality rate was 18.9%(n = 10), with five deaths directly attributed to PJI. Staphylococci accounted for 34 infections (63%), while 11(20.4%) had multiorganism infections and six culture-negative PJI. At the end of treatment 79.6%(n = 43) still had an implanted TJR, 7.4% (n = 4) had spacers, 5.6%(n = 3) had undergone resection arthroplasty, 3.7%(n = 2) arthrodesis, and one each amputation and exarticulation.

CONCLUSIONS

Mortality and specially complication rates were (are) high in this RA patients group presenting PJI. Delays to diagnosis and treatment may explain some of these poor outcomes.

LEVEL OF EVIDENCE

A cohort level III retrospective study.

Performance of classical serum inflammatory markers in healed and unhealed treated patients with joint and prosthetic joint infections

BACKGROUND

Serum markers, such as erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and D-dimer, are currently used by clinicians and orthopedic surgeons in diagnosing and managing joint infections (JI), although conflicting results exist on their performance. The aim of this study was to evaluate their performance in assessing healing or unhealing of patients with JI or with prosthetic joint infection (PJI).

METHODS

ESR, CRP and D-dimer serum levels were evaluated before, during and after antibiotic treatment in 61 patients (65.1 ± 12.6 years): 49 affected by PJI and 12 by JI, between 2020 and 2022. These patients had undergone orthopedic surgery and were treated with antibiotics.

RESULTS

ESR, CRP and D-dimer were significantly lower after treatment than before (p value: 0.001, 0.001 and 0.003, respectively) in healed and unhealed patients. A moderate correlation was found between the three inflammatory markers.

CONCLUSIONS

Using a cut off value of 25 mm/h for ESR, 0.5 mg/L for CRP, and 700 ng/ml for D-dimer, it might be possible to discriminate healed from unhealed patients (PPV and NPV: ESR 65.5% and 68.8%, CRP 71.9% and 79.3%, D-dimer 76.9% and 81.8%). The combined use of these three inflammatory markers might be useful in the management of joint infections.

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

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

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.

Graphic type differentiation of cell count data for diagnosis of early and late periprosthetic joint infection: A new method

BACKGROUND

Graphic type differentiation of cell count data of synovial aspirates is a new method for the diagnosis of early and late periprosthetic joint infection.

OBJECTIVE

The aim of the study was to analyse if the same 6 LMNE-types can be differentiated in the new Yumizen H500 cell counter as it was the case for the old cell counter ABX Pentra XL 80 of previous publications, to verify if the erythrocyte and thrombocyte curves of the new device give additional information and to calculate the difference of cell count in LMNE-type I and III (with abrasion) in the cell counter and in the manual counting chamber (Neubauer improved).

METHODS

450 aspirates of 152 total hip arthroplasties and 298 knee arthroplasties obtained for the diagnosis of periprosthetic joint infection were analysed with the Yumizen H500.

RESULTS

All LMNE-matrices of the 450 aspirates could assigned to one of the six LMNE-types. There were 76 LMNE-type I, 72 LMNE-type II, 14 LMNE-type III, 241 LMNE-type IV, 36 LMNE-type V and 12 LMNE-type VI. The erythrocyte and thrombocyte distribution curves were very helpful for differentiation of hematoma and infection. The cell count in the manual counting procedure was lower than in the cell counter: for the LMNE-type I (abrasion type) the median of the difference was 925/μL (median) and for the LMNE-type III (combined type of infection and abrasion) 3570/μL (median).

CONCLUSION

The described graphic type differentiation is a new and helpful method for differentiation of hematoma and early PJI as well as abrasion and late PJI.

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.

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.

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.

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.

A New Graphic Type Differentiation of Cell Account Determination for Distinguishing Acute Periprosthetic Joint Infection from Hemarthrosis

Aims: This study evaluates the value of a new graphic representation of cell count data of synovial fluid in the diagnosis of acute periprosthetic joint infection (PJI). Methods: A total of 75 patients with revisions of 48 primary total knee and 27 hip arthroplasties within the first six weeks after surgery were analyzed with cultivation of the synovial fluid and determination of its cell count as well as microbiological and histological analyses of the periprosthetic tissue obtained during the revision surgery using the ICM classification. The synovial fluid was additionally analyzed for graphic representation of the measured cells using LMNE-matrices. Results: A total of 38 patients (50.7%) had an infection. The following types of LMNE matrices could be differentiated: the indeterminate type (IV) in 14.7%, the infection type (II) in 5.3%, the hematoma type (V) in 33.3%, and the mixed type (VI; infection and hematoma) in 46.7%. Differentiation of LMNE types into infection (types II and VI) and non-infection (types IV and V) resulted in a sensitivity of 100%, a specificity of 97.3%, and a positive likelihood ratio of 37.0. The cell count measurement showed a sensitivity of 78.9%, a specificity of 89.2%, and a positive likelihood ratio of 7.3 at a cut-off of 10,000 cells. The percentage of polymorphonuclear leukocytes showed a sensitivity of 34.2%, a specificity of 100%, and a positive likelihood ratio of >200 at a cut-off of 90%. Conclusion: The graphic representation of the cell count analysis of synovial aspirates is a new and helpful method for differentiating between genuine early periprosthetic infections and postoperative hemarthrosis.

The Graphical Representation of Cell Count Representation: A New Procedure for the Diagnosis of Periprosthetic Joint Infections

Aim: This study was designed to answer the question whether a graphical representation increase the diagnostic value of automated leucocyte counting of the synovial fluid in the diagnosis of periprosthetic joint infections (PJI). Material and methods: Synovial aspirates from 322 patients (162 women, 160 men) with revisions of 192 total knee and 130 hip arthroplasties were analysed with microbiological cultivation, determination of cell counts and assay of the biomarker alpha-defensin (170 cases). In addition, microbiological and histological analysis of the periprosthetic tissue obtained during the revision surgery was carried out using the ICM classification and the histological classification of Morawietz and Krenn. The synovial aspirates were additionally analysed to produce dot plot representations (LMNE matrices) of the cells and particles in the aspirates using the hematology analyser ABX Pentra XL 80. Results: 112 patients (34.8%) had an infection according to the ICM criteria. When analysing the graphical LMNE matrices from synovia cell counting, four types could be differentiated: the type “wear particles” (I) in 28.3%, the type “infection” (II) in 24.8%, the “combined” type (III) in 15.5% and “indeterminate” type (IV) in 31.4%. There was a significant correlation between the graphical LMNE-types and the histological types of Morawietz and Krenn (p < 0.001 and Cramer test V value of 0.529). The addition of the LMNE-Matrix assessment increased the diagnostic value of the cell count and the cut-off value of the WBC count could be set lower by adding the LMNE-Matrix to the diagnostic procedure. Conclusion: The graphical representation of the cell count analysis of synovial aspirates is a new and helpful method for differentiating between real periprosthetic infections with an increased leukocyte count and false positive data resulting from wear particles. This new approach helps to increase the diagnostic value of cell count analysis in the diagnosis of PJI.

What is the performance of novel synovial biomarkers for detecting periprosthetic joint infection in the presence of inflammatory joint disease?

AIMS

The aim of this study was to further evaluate the accuracy of ten promising synovial biomarkers (bactericidal/permeability-increasing protein (BPI), lactoferrin (LTF), neutrophil gelatinase-associated lipocalin (NGAL), neutrophil elastase 2 (ELA-2), α-defensin, cathelicidin LL-37 (LL-37), human β-defensin (HBD-2), human β-defensin 3 (HBD-3), D-dimer, and procalcitonin (PCT)) for the diagnosis of periprosthetic joint infection (PJI), and to investigate whether inflammatory joint disease (IJD) activity affects their concentration in synovial fluid.

METHODS

We included 50 synovial fluid samples from patients with (n = 25) and without (n = 25) confirmed PJI from an institutional tissue bank collected between May 2015 and December 2016. We also included 22 synovial fluid samples aspirated from patients with active IJD presenting to Department of Rheumatology, the first Medical Centre, Chinese PLA General Hospital. Concentrations of the ten candidate biomarkers were measured in the synovial fluid samples using standard enzyme-linked immunosorbent assays (ELISA). The diagnostic accuracy was evaluated by receiver operating characteristic (ROC) curves.

RESULTS

BPI, LTF, NGAL, ELA-2, and α-defensin were well-performing biomarkers for detecting PJI, with areas under the curve (AUCs) of 1.000 (95% confidence interval, 1.000 to 1.000), 1.000 (1.000 to 1.000), 1.000 (1.000 to 1.000), 1.000 (1.000 to 1.000), and 0.998 (0.994 to 1.000), respectively. The other markers (LL-37, HBD-2, D-dimer, PCT, and HBD-3) had limited diagnostic value. For the five well-performing biomarkers, elevated concentrations were observed in patients with active IJD. The original best thresholds determined by the Youden index, which discriminated PJI cases from non-PJI cases could not discriminate PJI cases from active IJD cases, while elevated thresholds resulted in good performance.

CONCLUSION

BPI, LTF, NGAL, ELA-2, and α-defensin demonstrated excellent performance for diagnosing PJI. However, all five markers showed elevated concentrations in patients with IJD activity. For patients with IJD, elevated thresholds should be considered to accurately diagnose PJI. Cite this article: Bone Joint J 2021;103-B(1):32-38.

Progress in Prevention, Diagnosis, and Treatment of Periprosthetic Joint Infection

Periprosthetic joint infection (PJI) after joint replacement surgery is a severe complication associated with high morbidity and increased treatment costs. More than 25% of joint implant failures are attributed to PJI. PJI diagnosis and treatment methods have substantially improved in recent years. However, the prevalence of PJI remains high, primarily due to the increased prevalences of obesity, diabetes, and other underlying conditions. Moreover, increasing elderly prefers to total joint replacement surgery. However, due to frailty and comorbidities, most are at increased risk of infectious arthritis and artificial joint infection (PJI). Therefore, PJI management for the elderly requires multilevel and multiangle intervention. In this review, we summarize the risk factors and diagnostic methods currently available for PJI and discuss the current PJI prevention and treatment interventions, especially the management in older adults.

Does the Alpha Defensin ELISA Test Perform Better Than the Alpha Defensin Lateral Flow Test for PJI Diagnosis? A Systematic Review and Meta-analysis of Prospective Studies

BACKGROUND

Periprosthetic joint infection (PJI) following total joint arthroplasty is a serious complication that causes severe morbidity and adds a major financial burden to the healthcare system. Although there is plenty of research on the alpha-defensin (AD) test, a meta-analysis consisting of only prospective studies investigating AD's diagnostic efficacy has not been performed. Additionally, some important subgroups such as THA and TKA have not been separately analyzed, particularly regarding two commonly used versions of the AD test, the laboratory-based (ELISA) and lateral-flow (LF).

QUESTIONS/PURPOSES

(1) Does the AD ELISA test perform better in the detection of PJI than the AD LF test, in terms of pooled sensitivity and specificity, when including prospective studies only? (2) Are there differences in sensitivity or specificity when using AD ELISA and AD LF tests for PJI diagnosis of THA or TKA PJI separately?

METHODS

Following the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines, we included prospective studies describing the use of either AD test in the workup of pain after total joint arthroplasty (primary or revision, but not after resection arthroplasty). Fifteen studies (AD ELISA: 4; AD LF: 11) were included, with 1592 procedures. Subgroup data on THA and TKA could be retrieved for 1163 procedures (ELISA THA: 123; LF THA: 257; ELISA TKA: 228; LF TKA: 555). Studies not describing THA or TKA, those not using Musculoskeletal Infection Society (MSIS) criteria as the standard for determining the presence or absence of PJI, those not clearly reporting data for the AD test for the total cohort, and those describing data published in another study were excluded. Studies were not excluded based on follow-up duration; the MSIS criteria could be used within a few weeks, when test results were available. Quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 criteria. Study quality was generally good. The most frequent sources of bias were related to patient selection (such as unclear inclusion and exclusion criteria) and flow and timing (uncertainty in place and time of aspiration, for example). Heterogeneity was moderate to high; a bivariate random-effects model therefore was used. To answer both research questions, sensitivity and specificity were calculated for AD ELISA and LF test groups and THA and TKA subgroups, and were compared using z-test statistics and meta-regression analysis.

RESULTS

No differences were found between the AD ELISA and the AD LF for PJI diagnosis in the pooled cohorts (THA and TKA combined), in terms of sensitivity (90% versus 86%; p = 0.43) and specificity (97% versus 96%; p = 0.39). Differences in sensitivity for PJI diagnosis were found between the THA and TKA groups for the AD ELISA test (70% versus 94%; p = 0.008); pooled AD LF test sensitivity did not differ between THA and TKA (80% versus 87%; p = 0.20). No differences in specificity were found in either subgroup.

CONCLUSIONS

Both the AD ELISA and AD LF test can be used in clinical practice because both have high sensitivity and very high specificity for PJI diagnosis. The lower sensitivity found for diagnosis of PJI in THA for the AD ELISA test must be carefully interpreted because the pooled data were heterogenous and only two studies for this group were included. Future research should analyze TKAs and THAs separately to confirm or disprove this finding.

LEVEL OF EVIDENCE

Level II diagnostic study.

Synovial bone sialoprotein indicates aseptic failure in total joint arthroplasty

Background

Until today, a reliable diagnostic discrimination between periprosthetic joint infections (PJI) and aseptic failure (AF) after total joint arthroplasty (TJA) remains challenging. Nearly all recent research focused on synovial markers to be elevated in PJI rather than in AF patients. In this study, synovial bone sialoprotein (sBSP) was investigated in PJI and AF arthroplasty patients before revision surgery.

Methods

sBSP and C-reactive protein (CRP) were determined in synovial fluid samples of PJI (n = 13) patients fulfilling the MSIS criteria and AF (n = 25) patients. Beside descriptive analysis and comparison, computed statistics determined the area under the receiver operating characteristics curve (AUC) to evaluate the discrimination ability of the tested synovial markers.

Results

In patients with PJI according to the MSIS criteria, mean sBSP was significantly lower: 14.8 ng/ml (95% CI 5.5-24.1) vs. 38.2 ng/ml in the AF group (95% CI 31.1-45.3), p ≤ 0.001. Conversely, mean sCRP was significantly higher in PJI patients: 8.4 μg/ml (95% CI 0-17.2) vs. 1.8 μg/ml in the AF group (95% CI 0.9-2.8), p = 0.032. The AUC of sCRP in PJI patients was 0.71. The AUC of sBSP in AF revision arthroplasty patients was 0.83. The detection of osteolyses was not associated with higher sBSP concentrations.

Conclusions

Considering the MSIS criteria, significantly higher sBSP concentrations were found in synovial fluid samples of AF compared to PJI patients. sCRP showed only fair, sBSP good discrimination potential. If it is not clear whether PJI is present or not, sBSP may be considered as an add-on synovial marker.