Diagnosis Of Periprosthetic Joint Infection Research Articles

The role of D-dimer in periprosthetic joint infection: a systematic review and meta-analysis.

The current literature on diagnosis of periprosthetic joint infection (PJI) provides controversial evidence on the diagnostic accuracy of D-dimer. Therefore, this critical literature search and meta-analysis was aimed to summarize the diagnostic accuracy of D-dimer for diagnosing PJI. We searched MEDLINE, Scopus, and Web of Science, for studies on D-dimer for diagnosing PJI, according to the PRISMA flowchart. QUADAS was used for assessing study quality. Sensitivity, specificity, positive (PLR) and negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were analyzed using bivariate diagnostic random-effects model. The area under the receiver-operating curve (AUC-ROC) was calculated. Subgroup analysis and univariate meta-regression were carried out for detecting potential sources of heterogeneity. We included 12 articles, totaling 1,818 patients (539 with PJI). The pooled sensitivity and specificity of D-dimer for diagnosing PJI were 0.739 (95% CI: 0.616-0.833) and 0.785 (95% CI: 0.679-0.863). The pooled PLR, NLR, DOR were 3.359 (95% CI, 2.340-4.821), 0.295 (95% CI, 0.180-0.484), and 11.787 (95% CI, 5.785-24.018). The cumulative ROC plot displayed an AUC of 0.688 (95% CI, 0.663-0.713; p<0.001). No threshold effects could be observed. The type of blood sample was identified as possible source of heterogeneity for DOR (p=0.01). Evidence emerged from this meta-analysis suggests that D-dimer displays sufficient diagnostic accuracy to rule out PJI. The type of blood sample (plasma vs. serum) and the study design could influence the results in terms of DOR and sensitivity. However, further perspective studies would be needed to validate its potential diagnostic usefulness.

Accuracy and Cost-Effectivenss of a Novel Method for Alpha Defensins Measurement in the Diagnosis of Periprosthetic Joint Infections

BackgroundTwo methods for detecting synovial fluids alpha defensins are available: the enzyme-linked immunosorbent assay and the lateral flow test. For both, the proper role and accuracy remain uncertain. The purpose of this study was to assess the accuracy of the matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) for alpha defensin detection in synovial fluids of patients with total knee arthroplasty/total hip arthroplasty failures. The hypothesis was that the alpha defensin measurement through MALDI-TOF MS assay could be a high sensitive and specific test for periprosthetic joint infections (PJI) diagnosis as compared with Musculoskeletal Infection Society (MSIS) criteria. MethodsThe study included 138 patients. The 2018 MSIS criteria were used to diagnose PJIs. Synovial fluids were assessed for routinely synovial fluid tests and alpha defensin measurement through MALDI-TOF MS. Sensitivity, specificity, overall diagnostic accuracy, positive and negative predictive values, receiver operator curves, and area under the curve were calculated. ResultsAs per the 2018 MSIS criteria, 59 PJIs (43%) and 79 aseptic failures (57%) were diagnosed. The MALDI-TOF MS assay showed an overall accuracy of 94.9%. The sensitivity was 93%, the specificity was 96%, the positive predictive value was 95%, and the negative predictive value was 95%. Receiver operator curves analysis demonstrates an area under the curve of 0.95 (P < .001). ConclusionThe MALDI-TOF MS assay showed high sensitivity and specificity for alpha defensin detection in case of total knee arthroplasty/total hip arthroplasty failures. The advantages of the technology, such as the few milliliters of sample needed, the rapidity of obtaining results, and the cost-effectiveness of the procedure could make the MALDI-TOF MS alpha defensin assay a useful and widespread test in clinical practice.

The Utility of MRI With Multiacquisition Variable-Resonance Image Combination (MAVRIC) in Diagnosing Deep Total Hip Arthroplasty Infection.

Background: The 2010 American Academy of Orthopaedic Surgeons Clinical Practice Guidelines report insufficient evidence to address the diagnostic efficacy of magnetic resonance imaging (MRI) for periprosthetic joint infection (PJI). Questions/Purposes: The purpose of this study was to determine the utility of MRI with multiacquisition variable-resonance image combination (MAVRIC) metal artifact suppression techniques in diagnosing PJI in the setting of total hip arthroplasty (THA). Methods: Multiacquisition variable-resonance image combination MRIs obtained of THAs between November 2012 and November 2016 were queried. Radiology reports were classified as positive (suspicious for infection), negative (no features of infection), or inconclusive (infection cannot be excluded or correlation with aspiration suggested if clinically concerned). Chart review identified cases of deep PJI according to the modified Musculoskeletal Infection Society criteria. Results: Of 2156 MRIs of THAs included, MRI was concerning for infection in 1.8% (n = 39), inconclusive in 1.2% (n = 26), and negative in 97.0% (n = 2091). Deep PJI was identified in 53 (2.5%) patients, 30 of whom (56.6%) had conclusively positive finding on MRI (false-negative rate: 43.4%, sensitivity: 56.6%). Of 2103 aseptic THAs, only 9 (0.4%) MRIs were read as suspicious for infection (false-positive rate: 0.4%; specificity: 99.6%). Conclusion: Magnetic resonance imaging with MAVRIC is a highly specific test for PJI with a low false-positive rate. This indicates that when clinicians are provided with an MRI that unexpectedly suggests infection, a formal evaluation for infection is indicated. In patients with otherwise equivocal diagnostic findings, MRI may help confirm, but not refute, a diagnosis of PJI. Prospective study with more experienced image reviewers may further support the use of MRI in PJI.

Different diagnostic performance of plasma fibrinogen and D-dimer in periprosthetic joint infection: a propensity score matched study

BackgroundFibrinogen (Fbg) and D-dimer have been used as biomarkers for the diagnosis of periprosthetic joint infection (PJI). However, previous research has reported conflicting results on the diagnostic value of D-dimer in comparison to Fbg, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR).AimThis study aimed to: (1) determine the optimal threshold of plasma Fbg and D-dimer in the diagnosis of PJI and compare their diagnostic value to that of CRP and ESR; and (2) investigate whether Fbg and D-dimer perform differently than CRP and ESR as diagnostic indicators for different types of PJI.MethodsA total of 115 revision cases after total hip arthroplasty (THA) and total knee arthroplasty (TKA) were identified. Based on demographic characteristics, 25 culture-positive cases were matched to 50 culture-negative cases using propensity score matching. Sensitivity, specificity, receiver operating characteristics (ROC), negative predictive value (NPV), and positive predictive value (PPV) were calculated and compared.ResultsThe optimal thresholds were 2.72 mg/L for D-dimer, 3.655 g/L for Fbg, 12.64 mg/L for CRP, and 27 mm/h for ESR. Levels of plasma Fbg, D-dimer, CRP, and ESR were significantly higher in the culture-positive group than the culture-negative group. Fbg, D-dimer, CRP, and ESR showed sensitivity of 0.92, 0.56, 0.92, and 0.88, respectively, and showed specificity of 0.84, 0.96, 0.94, and 0.80, respectively. The ROC curve showed that CRP has the highest area under the curve (AUC) (0.94), followed by Fbg (0.90), ESR (0.87), and D-dimer (0.81).ConclusionsPlasma Fbg exhibited a similar diagnostic performance compared to CRP and ESR in predicting culture-positive results in PJI. Plasma D-dimer showed high specificity but low sensitivity. In our study, Fbg and D-dimer did not show better diagnostic performance with different pathogens and different types of PJI. Further studies are required to investigate the difference between serum D-dimer and plasma D-dimer in the arthroplasty population.

Diagnostic value of fluoroscopy-guided hip aspiration for periprosthetic joint infection.

To assess the value of preoperative joint aspiration in detecting periprosthetic joint infection (PJI) in patients undergoing revision hip arthroplasty and to compare these with the clinical findings, serum markers, and intraoperative findings. Fluoroscopically guided hip aspirations in patients with pain after hip arthroplasty were retrospectively reviewed from January 2014 to December 2018. All hips underwent subsequent revision hip arthroplasty. Antibiotics were discontinued at least 2weeks before the aspiration. The 2018 Musculoskeletal Infection Society (MSIS) criteria served as a standard of reference for PJI. Clinical, serum, synovial, and intraoperative parameters were recorded in all patients. Correlations between all parameters with PJI diagnosis were analyzed using linear and logistic regression models with ROC analysis. In 202 hips that included 91 septic hips, hip aspiration (AUC = 0.78) and intraoperative (0.80) parameters performed better than serum-based tests (0.64) and clinical parameters (0.68) in detecting PJI. Using MSIS criteria as a standard of reference, hip aspiration had a sensitivity of 64.0% and an accuracy of 78.5% for cultures and a sensitivity of 74.2% and an accuracy of 82.1% for synovial polymorphonuclear neutrophils% (PMN%). Results substantially improved sensitivity after excluding patients that were treated with antibiotics, particularly culture results. Preoperative hip aspiration showed good diagnostic performance in diagnosing PJI compared with MSIS criteria as a standard of reference. But a negative result from aspirate could not rule out PJI. Based on our findings, hip aspiration is an essential test for treatment planning in patients with pain after hip arthroplasty.

Clinical characteristics and risk factors for culture-negative periprosthetic joint infections

BackgroundCulture-negative periprosthetic joint infections (PJIs) can complicate diagnosis and management of PJI. This study aimed to identify risk factors for culture-negative PJI and differences in clinical characteristics between culture-positive and culture-negative PJI group.MethodsThis retrospective, cross-sectional study evaluated PJI cases obtained between January 2013 and October 2019 at our institution. These PJI cases were divided into culture-positive and culture-negative groups and then compared. The demographics, laboratory findings, and details of patient’s clinical characteristics were investigated. Univariate and multivariate logistic regression analysis were performed to investigate risk factors for culture-negative PJI.ResultsA total of 109 PJI cases were included in the analysis: 82 (75%) culture-positive and 27 (25%) culture-negative. The mean serum white blood cell (WBC) count, C-reactive protein level, and erythrocyte sedimentation rate in the culture-negative group were significantly lower than those in the culture-positive group (p < 0.05). There were no significant differences between the two groups regarding history of prior antibacterial administration or treatment success rates. Multivariate analysis identified a low serum WBC count as a risk factor for culture-negative PJI (odds ratio = 0.78; 95% confidence interval [CI] = 0.63–0.97; p = 0.027).ConclusionsA low serum WBC count is a risk factor for culture-negative PJI, but prior antimicrobial therapy is not. The results suggest that PJI cases with lower levels of systemic inflammation are likely to be culture-negative; therefore, the possibility of a culture-negative result should be considered in suspected cases of PJI with low inflammatory markers, regardless of prior antibiotic exposure.

Bias Does Not Exist in Treating Knee Periprosthetic Joint Infection Among Patients With Substance Use Disorder.

Debridement, antibiotics with implant retention (DAIR), and 2-stage revision are standard surgical interventions for treating knee periprosthetic joint infection (PJI). Patients with substance use disorder (SUD), especially addictive drug use disorder (DUD), have been shown to receive inferior medical care in many specialties compared with nonusers. The authors identified patients with a diagnosis of PJI after knee arthroplasty who received either DAIR or 2-stage revision with the Nationwide Inpatient Sample (NIS) database from 2010 to 2014. Patients were stratified into 2 groups, patients with DUD and nonusers, based on Diagnostic and Statistical Manual of Mental Disorders, 5th Edition, criteria. Descriptive analysis was conducted to show the national trend for knee PJI treatment among the 2 patient groups. Multivariate logistic regression was used to compare the prevalence of DAIR and 2-stage revision between these 2 groups, adjusted for likely confounders, including age, sex, income, race, and comorbidities. Among the 11,331 patients with knee infection, 139 (1.23%) had DUD. Compared with nonusers, patients with DUD were significantly younger (P<.001), had more chronic conditions (P<.001), and were predominantly in lower income quartiles (P=.046). The 2 groups did not differ in sex and race (P=.072 and P=.091, respectively). The authors found that 30.22% of patients with DUD and 36.36% of nonusers received DAIR. The difference in these proportions was not statistically significant (P=.135). The results did not change after adjustment for confounding factors (P=.509). The findings suggested that bias does not exist among orthopedic surgeons who choose DAIR or 2-stage revision for knee PJI among patients with DUD. [Orthopedics. 2021;44(3):e385-e389.].

Better choice of the type of specimen used for untargeted metagenomic sequencing in the diagnosis of periprosthetic joint infections.

As a proven and comprehensive molecular technique, metagenomic next-generation sequencing (mNGS) has shown its potential in the diagnosis of pathogens in patients with periprosthetic joint infection (PJI), using a single type of specimen. However, the optimal use of mNGS in the management of PJI has not been explored. In this study, we evaluated the diagnostic value of mNGS using three types of specimen with the aim of achieving a better choice of specimen for mNGS in these patients. In this prospective study, 177 specimens were collected from 59 revision arthroplasties, including periprosthetic tissues, synovial fluid, and prosthetic sonicate fluid. Each specimen was divided into two, one for mNGS and one for culture. The criteria of the Musculoskeletal Infection Society were used to define PJI (40 cases) and aseptic failure (19 cases). The sensitivity and specificity of mNGS in the diagnosis of PJI were 95% and 94.7%, respectively, for all types of specimen. The sensitivity and specificity were 65% and 100%, respectively, for periprosthetic tissues, 87.5% and 94.7%, respectively, for synovial fluid, and 92.5% and 94.7%, respectively, for prosthetic sonicate fluid. The mNGS of prosthetic sonicate fluid outperformed that for other types of specimen in the rates of detection of pathogens (84.6%), sequencing reads (> ten-fold) and the rate of genome coverage (> five-fold). mNGS could serve as an accurate diagnostic tool in the detection of pathogens in patients with a PJI using three types of specimen. Due to its superior perfomance in identifying a pathogen, mNGS of prosthetic sonicate fluid provides the most value and may partly replace traditional tests such as bacteriological culture in these patients. Cite this article: Bone Joint J2021;103-B(5):923-930.

Variability and Interpretation of Synovial Cell Count and Differential: A Perspective in Hip and Knee Arthroplasty.

Multiple threshold values have been proposed for synovial leukocyte count (white blood cell count) and synovial neutrophil percentage (percent polymorphonuclear neutrophils) in the diagnosis of periprosthetic joint infection (PJI). The objective of this study was to elucidate the variability of these criteria under diverse patient/surgical settings. Hip PJIs yield higher synovial white blood cell counts and percent polymorphonuclear neutrophils than knee PJIs. Periprosthetic joint infection of failed unicompartmental knee arthroplasty produces a higher white blood cell count than that of failed total knee arthroplasty. Synovial white blood cell count and percent polymorpho-nuclear neutrophils PJI thresholds also vary in patients with antibiotic cement spacers and depend on the timing from primary arthroplasty (<6 weeks vs >6 weeks). Similarly, test results should be carefully interpreted for patients with comorbidities so that PJI is not missed or falsely identified. [Orthopedics. 2021;44(3):e320-e325.].

Complications Associated With Intravenous Antibiotic Treatment for Cutibacterium acnes Periprosthetic Shoulder Infection.

Whether positive Cutibacterium acnes cultures during revision shoulder arthroplasty represent true periprosthetic joint infection (PJI), deep tissue inoculant, or laboratory contaminant is a point of substantial controversy. The purpose of this study was to review complications of intravenous antibiotics used for treatment of presumed C acnes shoulder PJI. A study population of 26 patients treated for C acnes PJI with a minimum follow-up of 2 years after operative treatment was established. Complication occurrence and severity were obtained through chart review and phone survey. Sixteen (61.5%) patients experienced a therapeutic complication. Twelve (46.2%) patients experienced a total of 47 antibiotic-associated adverse effects and 10 (38.5%) patients experienced 11 total peripherally inserted central catheter line-associated complications. Female sex carried an increased risk for severe complications (relative risk, 3.3; 95% CI, 1.2-9.5; P=.024). Treatment duration of greater than 6 weeks was a significant predictor for the total number of complications experienced [F(1,23)=5.361; P=.030; adjusted R2=0.189]. Age older than 65 years, treatment duration greater than 6 weeks, and female sex were significant predictors for the number of severe complications [F(3,21)=3.249; P=.042; adjusted R2=0.219]. Treating C acnes infection with intravenous antibiotics carries a substantial risk of adverse events, highlighting the importance of accurate diagnosis of shoulder PJI. Further investigations into the efficacy and safety profile of oral antibiotics for shoulder PJI are necessary. [Orthopedics. 2021;44(3):e422-e426.].

A retrospective comparison of thromboelastography and conventional coagulation parameters for periprosthetic joint infection diagnosis and reimplantation timing

PurposeThe diagnostic significance of coagulation parameters in periprosthetic joint infection (PJI) is currently attracting increasing attention. We assessed the diagnostic accuracy of thromboelastography (TEG) for PJI and compared the values of various coagulation indicators for PJI diagnosis and reimplantation timing. MethodsWe enrolled 250 patients undergoing revision for aseptic failure (Group A), revision for PJI (Group B), or reimplantation (Group C) during 2013–2020. C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), representative coagulation-related indicators (reaction time [R], clotting time [K], angle and maximum amplitude [MA]) of TEG and routine coagulation indicators, including fibrinogen, D-dimer, fibrin degradation product (FDP), platelets count (PC), mean platelet volume (MPV), distribution width (PDW) and plateletcrit (PCT) as well as PC/MPV ratio(PVR)were measured preoperatively. Receiver operating characteristic (ROC) curves were used to evaluate the utility of all tested indicators for assessing infection. ResultsAll the indicators showed significant differences between groups A and B (P < 0.05) and, except for D-dimer, FDP, MPV and R, between groups B and C (P < 0.05). Similar differences were also observed in biomarkers before first-stage revision and second-stage reimplantation. ROC curves showed that fibrinogen, K, angle and MA outperformed the other coagulation indicators, with areas under the curve of 0.864 to 0.893 and threshold values of 3.55 g/L, 1.2 min, 72.4 deg and 69.1 mm, respectively. The multiple tests of TEG indices (K, angle and MA) and traditional inflammatory markers (CRP and ESR) or conventional coagulation indicators (fibrinogen, PC and PVR) had good sensitivity and specificity for PJI diagnosis, and the diagnostic values of TEG and platelet-associated indicators (PC and PVR) varied in the different subgroups. ConclusionTEG was closely related to PJI and could serve as a valuable technique for identifying residual infection before reimplantation. Fibrinogen showed high diagnostic accuracy for PJI and effectively guided the timing of reimplantation.

CORR Insights®: What Is the Optimal Timing for Reading the Leukocyte Esterase Strip for the Diagnosis of Periprosthetic Joint Infection?

CORR Insights®: What Is the Optimal Timing for Reading the Leukocyte Esterase Strip for the Diagnosis of Periprosthetic Joint Infection?

Introducing image-guided synovial aspiration and biopsy in assessing peri-prosthetic joint infection: an early single-centre experience.

Synovial sampling can be used in the diagnosis of peri-prosthetic joint infection (PJI). The purpose of this study was to establish the role of simultaneous image-guided synovial aspiration and biopsy (SAB) during an initial 2-year experience at our institution. Retrospective review of consecutive SABs performed during 2014-2016 at a tertiary referral musculoskeletal centre. Radiological SAB microbiology culture results were compared with intra-operative surgical samples or multidisciplinary team (MDT) meeting outcome at 1-year follow-up if surgery was not undertaken. Sensitivity, specificity and accuracy of synovial aspiration (SA), synovial biopsy (SB) and simultaneous SAB were calculated. 103 patients (46 male, 57 female) totalling 111 procedures were analysed with mean age 65years (range 31-83). Image-guided synovial procedures were performed on 52 (46.9%) hip and 59 (53.1%) knee joint prostheses. The mean combined sensitivity, specificity and accuracy for the entire cohort was 72.6%, 96.9% and 90%, respectively. When only SB was obtained, diagnostic accuracy (92.5%) was similar to SA alone (94.1%). In total, there were 21 (18.9%) true-positive, 80 (72.1%) true-negative, 2 (1.8%) false-positive and 8 (7.2%) false-negative cases (PPV 91.3% and NPV 90.9%). No post-procedural complications were recorded at 1-year follow-up. Percutaneous image-guided SAB is a valuable technique in assessing suspected PJI, with most samples indicative of infective status and causative organisms when validated against intra-operative results and specialist MDT evaluation. Image-guided SB is a safe and useful additional procedure following failed SA with equivalent levels of diagnostic accuracy.

Diagnostic Utility of a Novel Point-of-Care Test of Calprotectin for Periprosthetic Joint Infection After Total Knee Arthroplasty: A Prospective Cohort Study.

Despite several synovial fluid biomarkers for the diagnosis of periprosthetic joint infection (PJI) having been investigated, point-of-care (POC) tests using these biomarkers are not widely available. Synovial calprotectin has recently been reported to effectively exclude the diagnosis of PJI. Thus, the objective of this study was to test the value of a calprotectin POC test for PJI diagnosis in patients undergoing total knee arthroplasty (TKA) using the 2013 Musculoskeletal Infection Society (MSIS) PJI diagnosis criteria as the gold standard. Synovial fluid samples were prospectively collected from 123 patients who underwent revision TKA at 2 institutions within the same health-care system from October 2018 to January 2020. The study was conducted under institutional review board approval. Data collection comprised demographic, clinical, and laboratory data in compliance with the MSIS criteria. Synovial fluid samples were analyzed by calprotectin POC tests in accordance with the manufacturer's instructions. Revisions were categorized as septic or aseptic using MSIS criteria by 2 independent reviewers blinded to the calprotectin results. Calprotectin test performance characteristics with sensitivities, specificities, positive predictive values, negative predictive values, and areas under the receiver operating characteristic curve (AUC) were calculated for 2 different PJI diagnosis scenarios: (1) a threshold of ≥50 mg/L, and (2) a threshold of ≥14 mg/L. According to the MSIS criteria, 53 revision TKAs were septic and 70 revision TKAs were aseptic. In the ≥50-mg/mL threshold scenario, the calprotectin POC performance showed a sensitivity of 98.1%, a specificity of 95.7%, a positive predictive value of 94.5%, a negative predictive value of 98.5%, and an AUC of 0.969. In the ≥14-mg/mL threshold scenario, the sensitivity was 98.1%, the specificity was 87.1%, the positive predictive value was 85.2%, the negative predictive value was 98.4%, and the AUC was 0.926. The calprotectin POC test has excellent PJI diagnostic characteristics, including high sensitivity and specificity in patients undergoing revision TKA. This test could be effectively implemented as a rule-out test. However, further investigations with larger cohorts are necessary to validate these results. Diagnostic Level I. See Instructions for Authors for a complete description of levels of evidence.

Microbiological diagnosis of polymicrobial periprosthetic joint infection revealed superiority of investigated tissue samples compared to sonicate fluid generated from the implant surface

ObjectivesIn the microbiological diagnosis of periprosthetic joint infection (PJI), there is much discussion about the methodology of obtaining proper specimens, the processing technique, and suitable culture media. This retrospective study was conducted to analyse the accuracy of our culture techniques. MethodsTissue samples and components from 258 patients after revision arthroplasty of the hip, knee, and shoulder were investigated, and the results of tissue cultures (TC) were compared to those of sonicate fluid cultures (SFC). Furthermore, an evaluation was performed of the influence of different culture media on the detection rate. ResultsPJI was confirmed in 186 patients. The overall sensitivity of TC was no different to that of SFC (91.3% vs 90.8%, P = 1). In 153 cases (82.3%), TC and SFC showed concordant positive results. Results were discordant in 33 cases (17.7%). When differentiated according to the type of infection, TC showed significantly better results than SFC in detecting polymicrobial infections (97.0% vs 67.0%, P = 0.004). There were also significant differences between the culture media regarding the yield of microorganisms. ConclusionsTC was more effective in detecting co-infections. The best results were obtained using both TC and SFC. The choice of culture media has a significant influence on the quality of results.

Diagnostic accuracy of the BJI InoPlex™ (Diaxonhit) immunoassay on blood samples for periprosthetic joint infection in complex microbiological situations. Preliminary results of 24 cases in a French Reference Center for Complex Bone and Joint Infection (CRIOAC)

BackgroundWhile joint aspiration is the benchmark for diagnosing periprosthetic joint infections (PJI), the results can be flawed because certain bacteria are difficult to culture, the patient is on concurrent antibiotic therapy or in some cases, repeated joint aspirations confer conflicting results. The BJI InoPlex™ (Diaxonhit) is a multiplex ELISA (Enzyme Linked Immunosorbent Assay) that measures the immune response (presence of specific IgG) to certain bacterial species from three families: Staphylococcus (8 antigens) epidermidis, aureus and lugdunensis, Streptococcus B (4 antigens) and Cutibacterium acnes (4 antigens). This assay is done with peripherally collected blood. However, there are few published studies about this assay, especially if the microbiological diagnosis is in doubt in cases of suspected chronic PJI. This led us to conduct a retrospective study in a French tertiary care center to determine 1) the sensitivity and specificity of the BJI InoPlex™, 2) its positive (PPV) and negative predictive value (NPV) and 3) what causes diagnostic errors. HypothesisThe BJI InoPlex has a sensitivity/specificity and PPV/NPV above 75%. Materials and methodsThe BJI InoPlex was used 24 times on 24 patients between January 2016 and January 2017 in scenarios where the microbiological diagnosis was difficult: 1 with on-going antibiotic therapy, 13 conflicting repeat joint aspirations, 10 negative cultures with history of infection and/or clinical evidence of a PJI. The series consisted of 11 hip arthroplasty and 13 knee arthroplasty cases. The results of the BJI InoPlex test were compared to the MusculoSkeletal Infection Society (MSIS) the criteria for a joint infection. ResultsFor the bacterial species covered by the test, the sensitivity of the BJI InoPlex for diagnosing a chronic PJI based on the 2018 MSIS criteria was 50%, the specificity was 56%, the PPV was 36% and the NPV was 69%. DiscussionWhile innovative, minimally invasive, and rapid (results in a few hours), the BJI InoPlex does not provide an effective diagnosis of chronic PJI in complex microbiological situations. In this study, we used the test in the most difficult situations possible and on a small number of patients, which may explain why the results were not as good as in other studies. Its current performance and cost mean there is no role for it in our algorithm for treating patients with a suspected PJI, contrary to other biomarkers. Its spectrum must include other bacterial strains involved in chronic PJI. Knowledge of the specific infectious agent increases its diagnostic value, it could be used to monitor the outcome of a PJI, although other studies would be needed to support this use. Level of evidenceIV–Retrospective diagnostic study.

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

IntroductionThe diagnosis of periprosthetic joint infection (PJI) can be challenging and rests on several principles. The use of diagnostic biomarkers, such as the synovial C-Reactive Protein (CRP), seems promising. The purpose of this study was to determine whether synovial CRP was a more discriminating test than serum CRP for the diagnosis of hip and knee PJI. Materials and methodsIn total, 194 patients were included in this single center prospective study: 42 primary arthroplasties (control group [CG]), 111 revisions for aseptic prosthesis (aseptic revision group [ARG]), and 41 revisions for septic prosthesis (septic revision group [SRG]) based on the Musculoskeletal Infection Society (MSIS) criteria. ResultsThe serum and synovial CRP levels were significantly higher in the SRG than the other two groups (SRG serum CRP=75.6mg/L vs. ARG serum CRP=6mg/L and CG serum CRP=2.7mg/L, p<0.001; SRG synovial CRP=31.5mg/L vs. CG synovial CRP=2.6mg/L and ARG synovial CRP=1.7mg/L, p<0.001). The positive likelihood ratios (LR+) were very similar for both the synovial CRP cut-off value of 4.4mg/L (LR+=7.04; sensitivity [Se] 82.5%, specificity [Sp] 88.3%) and the serum CRP cut-off value of 9mg/L (LR+=6.3; Se 87.5%, Sp 86.1%). ConclusionThis study showed that synovial CRP testing was not more discriminating than serum CRP in the diagnosis of hip and knee PJI. A serum CRP level greater than 9mg/L was a sign of PJI. Level of evidenceIII; case-control study.

Low value of platelet count to mean platelet volume ratio to diagnose chronic PJI: A case control study

IntroductionNumerous tests are being evaluated in order to aid the diagnosis of periprosthetic infections since it is a complicated and sometimes inconclusive process. The purpose of this study was to assess the diagnostic performance of platelet count to mean platelet volume ratio as a tool to aid the diagnosis of periprosthetic joint infections. The investigated questions were: “Is platelet count/mean platelet volume ratio more sensitive or specific than C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR) in the diagnosis of periprosthetic joint infections?” and “Does platelet count/mean platelet volume ratio increase the accuracy of periprosthetic joint infection diagnosis?”. HypothesisPlatelet count/mean platelet volume ratio increases the accuracy of periprosthetic joint infection diagnosis. Materials and methodsThis study was performed retrospectively on patients who underwent revision hip or knee arthroplasty between 2016 and 2019. 62 patients with 33 aseptic (AR) and 29 septic revision (SR) who met our inclusion criteria were included. The sensitivity, specificity and diagnostic performance of CRP, ESR and platelet count/mean platelet volume values were analyzed and compared. ResultsThe demographic characteristics were similar between groups. Staphylococcus aureus and Staphylococcus epidermidis were the most commonly encountered microorganisms, while seven patients had negative cultures in SR group. ESR, CRP and platelet count/mean platelet volume values were significantly higher in SR group compared to AR group (p<0.01). ROC analysis for platelet count/mean platelet volume ratio revealed a cut-off value at 35.3 which provided 75.9% sensitivity and 78.8% specificity for periprosthetic joint infections. Platelet count/mean platelet volume ratio yielded lower sensitivity and similar specificity compared to ESR and CRP values. Platelet count/mean platelet volume had a lower area under curve value, indicating a poorer diagnostic performance compared to ESR and CRP. DiscussionThe diagnostic performance of platelet count/mean platelet volume ratio is low and current findings do not support its usage to increase the accuracy of periprosthetic joint infections diagnosis. Level of evidenceIII; diagnostic case-control study.

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.

Exciting Performance of Plasma Fibrinogen in Periprosthetic Joint Infection Diagnosis.

ObjectiveTo test the significance of serum C‐reactive protein (CRP), the erythrocyte sedimentation rate (ESR), the platelet count/mean platelet volume ratio (PC/MPV), plasma fibrinogen, and D‐Dimer in periprosthetic joint infection (PJI) diagnosis.MethodsWe retrospectively analyzed the clinical data of 149 patients diagnosed from July 2016 to December 2019 with primary osteoarthritis (OA group, average age 63.18 years [range, 53–82 years] 18 males, 46 females), PJI (PJI group, average age 63.74 years [range, 52–81 years], 16 males, 31 females), and aseptic loosening (aseptic group, average age 63.18 years [range, 53–80 years], 12 male, 26 female) in our department. Demographic data and the sensitivity and specificity of preoperative CRP, ESR, PC/MPV, fibrinogen, and D‐Dimer in PJI diagnosis were compared.ResultsThere were no significant differences when the demographic data of the three groups were compared. The expression level of CRP (50.67 ± 58.98 mg/L), ESR (50.55 ± 25.81 mm/h), PC/MPV (35.79 ± 18.00), and fibrinogen (4.85 ± 1.33 μg/mL) in the PJI group were higher than in the OA group (CRP: 4.09 ± 9.68 mg/L; ESR:13.44 ± 9.32 mm/1 h; PC/MPV: 24.97 ± 7.58; fibrinogen: 3.09 ± 0.55 μg/mL) and the aseptic group (CRP: 7.01 ± 11.83 mg/L; ESR: 22.47 ± 17.53 mm/1 h; PC/MPV: 25.18 ± 11.48; fibrinogen: 3.39 ± 0.80 μg/mL), respectively. The expression level of plasma D‐dimer (1.60 ± 1.29 mg/L) in the PJI group was higher than in the OA group (0.49 ± 0.42 mg/L) but similar to that in the aseptic group (1.21 ± 1.35 mg/L). Receiver operating characteristic (ROC) curve analysis demonstrated that the areas under the ROC curve (AUC) for CRP, ESR, PC/MPV, fibrinogen, and D‐dimer were 0.892 (95% confidence interval, 0.829–0.954), 0.888 (0.829–0.947), 0.686 (0.589–0.784), 0.873 (0.803–0.943), and 0.835 (0.772–0.899), respectively. When PC/MPV > 31.70, fibrinogen >4.01 μg/mL, and D‐dimer >1.17 mg/L were set as the threshold values for the diagnosis of PJI, the sensitivity of PC/MPV in PJI diagnosis was lower than that of ESR and plasma fibrinogen. In contrast, there was no significant difference when comparing the specificity of CRP, ESR, PC/MPV, fibrinogen, and D‐dimer in PJI diagnosis.ConclusionPlasma fibrinogen is a good new auxiliary diagnostic marker for PJI.