Synovial Fluid Alpha-defensin Research Articles

Synovial Fluid Alpha-defensin Lateral Flow Assay is Specific but Not Sensitive for Periprosthetic Joint Infection in Revision Arthroplasty: A Propensity Score-matched Analysis

Synovial Fluid Alpha-defensin Lateral Flow Assay is Specific but Not Sensitive for Periprosthetic Joint Infection in Revision Arthroplasty: A Propensity Score-matched Analysis

It can be unnecessary to combine common synovial fluid analysis and alpha-defensin tests for periprosthetic joint infection diagnosis

BackgroundPeriprosthetic joint infection is a serious complication after total joint arthroplasty. Despite that alpha-defensin was used as diagnostic test in the 2018 ICM (international consensus meeting) criteria, its position in the PJI diagnostic pipeline was controversial. Therefore, we performed a retrospective pilot study to identify whether synovial fluid alpha-defensin test was necessary when corresponding synovial fluid analysis (WBC count, PMN% and LE tests) was performed.MethodsBetween May 2015 and October 2018, a total of 90 suspected PJI patients who underwent revisions after TJA were included in this study. Based on the 2018 ICM criteria, the interobserver agreements between preoperative diagnostic results and postoperative diagnostic results and the interobserver reliability between preoperative diagnostic results and postoperative diagnostic results with or without synovial fluid alpha-defensin tests were calculated. After that, the ROC analysis, and the direct cost-effectiveness of adding alpha-defensin was performed.ResultsThere were 48,16 and 26 patients in the PJI group, inconclusive group and non-PJI group, respectively. Adding the alpha-defensin tests into 2018 ICM criteria can’t change the preoperative diagnostic results, postoperative diagnostic results, and the concordance between preoperative and postoperative diagnostic results. Moreover, the Risk–benefit Ratio is over 90 per changed decision and the direct cost-effectiveness of alpha-defensin was more than $8370($93*90) per case.ConclusionsAlpha-defensin assay exhibit high sensitivity and specificity for PJI detection as a standalone test based on the 2018 ICM criteria. However, the additional order of Alpha-defensin can’t offer additional evidence for PJI diagnosis when corresponding synovial fluid analysis was performed (synovial fluid WBC count, PMN% and LE strip tests).Evidence levelLevel II, Diagnostic study.

Infection after total joint replacement of the hip and knee: research programme including the INFORM RCT

Infection after total joint replacement of the hip and knee: research programme including the INFORM RCT

Synovial fluid alpha-defensin in periprosthetic knee infection workup : liquid chromatography-mass spectrometry detection of alpha-defensin in synovial fluid.

The diagnosis of periprosthetic joint infection (PJI) continues to present a significant clinical challenge. New biomarkers have been proposed to support clinical decision-making; among them, synovial fluid alpha-defensin has gained interest. Current research methodology suggests reference methods are needed to establish solid evidence for use of the test. This prospective study aims to evaluate the diagnostic accuracy of high-performance liquid chromatography coupled with the mass spectrometry (LC-MS) method to detect alpha-defensin in synovial fluid. Between October 2017 and September 2019, we collected synovial fluid samples from patients scheduled to undergo revision surgery for painful total knee arthroplasty (TKA). The International Consensus Meeting criteria were used to classify 33 PJIs and 92 aseptic joints. LC-MS assay was performed to measure alpha-defensin in synovial fluid of all included patients. Sensitivity, specificity, positive predictive value, negative predictive value, and the area under the receiver operating characteristic curve (AUC) were calculated to define the test diagnostic accuracy. The AUC was 0.99 (95% confidence interval (CI) 0.98 to 1.00). Receiver operating characteristic (ROC) analysis showed that the optimal cut-off value of synovial fluid alpha-defensin was 1.0 μg/l. The sensitivity of alpha-defensin was 100% (95% CI 96 to 100), the specificity was 97% (95% CI 90 to 98), the positive predictive value was 89.2% (95% CI 82 to 94), and negative predictive value was 100% (95% CI 96 to 100). ROC analysis demonstrated an AUC of 0.99 (95% CI 0.98 to 1.0). The present study confirms the utility of alpha-defensin in the synovial fluid in patients with painful TKA to select cases of PJI. Since LC-MS is still a time-consuming technology and is available in highly specialized laboratories, further translational research studies are needed to take this evidence into routine procedures and promote a new diagnostic approach.Cite this article: Bone Joint J2022;104-B(9):1047-1051.

Development of a multiplex and sensitive lateral flow immunoassay for the diagnosis of periprosthetic joint infection

The diagnosis of periprosthetic joint infection (PJI) remains a challenge. However, recent studies showed that synovial fluid biomarkers have demonstrated greater diagnostic accuracy than the currently used PJI diagnostic tests. In many diagnostic tests, combining several biomarkers into panels is critical for improving diagnostic efficiency, enhancing the diagnostic precision for specific diseases, and reducing cost. In this study, we prove that combining alpha-defensin and C-reactive protein (CRP) as biomarkers possesses the potential to provide accurate PJI diagnosis. To further verify the result, we developed a multi-target lateral flow immunoassay strip (msLFIA) with staking pad design to obtain on-site rapid response for clinical diagnosis of PJI. A total of 10 synovial fluid samples were tested using the msLFIA, and the results showed that the combined measurements of synovial fluid alpha-defensin and CRP levels were consistent with those obtained from a commercial enzyme-linked immunosorbent assay kit. In addition, we developed a multi-target lateral flow immunoassay strip (msLFIA) with staking pad design to obtain on-site rapid response for clinical diagnosis of PJI, which the multi-target design is used to increase specificity and the stacking pad design is to enhance detection sensitivity. As a result, the turnaround time of the highly sensitive test can be limited from several hours to 20 min. We expect that the developed msLFIA possesses the potential for routine monitoring of PJI as a convenient, low-cost, rapid and easy to use detection device for PJI.

A Case Report and Literature Review to Aid in the Management of Trunnion Failure in Hip Arthroplasty Patients: Can Trunnionosis and Prosthetic Joint Infection Co-Exist?

Trunnionosis is a type of corrosion and wear at the head-neck taper junction of the femoral implant, and it can be a slow and silent catastrophe. Simultaneous prosthetic joint infection (PJI) is occasionally possible based on the fulfillment of a few of the minor criteria from the Musculoskeletal Infection Society (MSIS), but the existing literature lacks adequate evidence to support that the infection actually exists. We are presenting a case of an 82-year-old man with right total hip arthroplasty performed over a decade prior to presenting to the emergency room with a sudden-onset pop followed by groin pain and difficulty in walking. Radiographs showed a dissociated femoral implant at the level of trunnion with malalignment and heterotopic ossification. Metal Artifact Reduction Sequence MRI of the right hip showed mixed type-two and type-three pseudotumors, and atrophy of surrounding abductor muscles. The erythrocyte sedimentation rate was within normal limits, C-reactive protein was borderline raised, and serum cobalt-chromium levels were elevated without any signs of systemic metal toxicity. Hip joint aspirate revealed blood-stained fluid flooded with red blood cells, leukocytes and neutrophils, and a positive alpha-defensin assay. These findings were interpreted as positive for prosthetic joint infection. Intraoperatively, there was severe wear of the inferomedial aspect of the femoral head-neck junction and extensive metallosis throughout the right hip. Tissue and fluid specimens were sent for cultures, sensitivities, and histopathology for pseudotumor and infection evaluation. An articulating antibiotic spacer was then placed with the intent to perform a staged reconstruction of the femur and right acetabulum. Final synovial, bone, and soft tissue cultures, as well as histopathological photomicrograph of the tissue slides, were negative for infection. This case demonstrates the striking features of metallosis associated with trunnion failure of a metal-on-polyethylene total hip joint prosthesis that was simultaneously showing signs of prosthetic infection by satisfying the minor criteria according to the latest guidelines by the MSIS with a strikingly high cell count of red blood cells in the synovial fluid exam, indicating inflamed hyper-vascular pseudotumors vs. hemarthrosis vs. bloody tap. Diagnostic dilemma led by positive synovial fluid alpha defensin, high synovial neutrophil and white cell count results with negative final cultures or infection on histological slides raises concern that infection was not present and two-stage revision arthroplasty with six weeks of antibiotics was not necessary along with increased risk of morbidity, mortality as well as cost of care.

Improved diagnostic accuracy with the classification tree method for diagnosing low-grade periprosthetic joint infections by quantitative measurement of synovial fluid alpha-defensin and C-reactive protein.

The diagnosis of low-grade periprosthetic joint infections (PJIs) is challenging, because patients may present with unspecific symptoms, false-negative cultures, or marginally elevated values of serum biomarkers like C-reactive protein (CRP). This may lead to the unintended implantation of a revision prosthesis into an infected surgical site with a repeat risk of short-term failure. Conversely, false diagnosis of joint infection may result in multistage revision procedures, which expose the patient to unnecessary surgical procedures and inappropriate antibiotic treatment. Here, we investigated whether synovial biomarkers can preoperatively distinguish between aseptic prosthesis loosening and low-grade joint infection and the most accurate biomarker combinations. Inclusion criteria for the study were indication for revision arthroplasty due to aseptic implant failure, acute high-grade infection, or (suspected) low-grade infection. We prospectively collected synovial fluid of patients undergoing revision arthroplasty for quantitative measurement of alpha defensin, CRP, interleukin (IL-6), IL-10, and lipopolysaccharide binding protein (LBP). The classification tree method revealed alpha defensin and CRP as the most suitable biomarker combination to distinguish between aseptic loosening and low-grade joint infection. The combination of CRP > 2.0mg/L and alpha defensin > 90.000pg/mL correctly identified nine of 11 patients with low-grade infection. Alpha defensin plus CRP seems to be the most helpful combination for pre-operative discrimination of aseptic loosening vs. low-grade joint infection.

Infection: It's a Numbers Game: Commentary on an article by William Z. Stone, MD, et al.: "Clinical Evaluation of Synovial Alpha Defensin and Synovial C-Reactive Protein in the Diagnosis of Periprosthetic Joint Infection".

Commentary Our ability to continue to safely perform arthroplasty depends on our ability to control infection. With bacterial resistance, we may need progress just to keep up. Progress depends on definitions, measures, and qualitative and quantitative clarity. So far, we do not agree on much about revision arthroplasty with the exception of the impact of periprosthetic joint infection1. The road to understanding is long, but in their article, Stone et al. advance the journey. Not all constructive ideas can be retrieved on an electronic search. Readers should correct me when I attribute the idea that “all arthroplasties are infected all the time” to Professor Reg Elson of the University of Sheffield (past president of the British Hip Society). With some mischief, he suggested that bacteria are always present in an arthroplasty, “in balance” with the patient’s immune surveillance. Upset the equilibrium, and periprosthetic joint infection results. Recent research into the human microbiome supports the complex relationship between humans and bacteria2. When does that relationship become a periprosthetic joint infection? Surgeons categorize everything as sterile or contaminated: there are either no bacteria or some bacteria. Sharper minds recognize that clinical infection is a numbers game. The classic laboratory study by Zimmerli et al. showed that rats tolerate a much larger inoculum without clinical infection in the absence of foreign material, but sustain infection with many fewer bacteria when metal implants are present3. It makes sense that periprosthetic joint infection can be diagnosed by the host’s response, rather than the bacteria themselves. C-reactive protein (CRP) appears in reaction to the C-polysaccharide of Pneumococcus and was identified decades ago4. We depend on this laboratory test daily when infection is suspected. Another marker, alpha defensin, can diagnose periprosthetic joint infection, but how dependable is it? The article by Stone et al. originates from clinicians who did not develop the alpha defensin assay. They evaluated the ability of synovial fluid alpha defensin alone and in combination with synovial fluid CRP to identify periprosthetic joint infection as defined by Musculoskeletal Infection Society (MSIS) criteria. The assays were good, but not a perfect match. The synovial fluid alpha defensin missed 7 infections, mainly with low-virulence organisms. When synovial fluid CRP was added, 3 of the 7 infected cases were still overlooked. Although patients were advised to stop antibiotics before the assay, there is no way to verify if they did or the effect of exposure. The synovial fluid alpha defensin test overdiagnosed infection in 4 patients with metallosis and 2 patients with only 2 minor MSIS criteria for periprosthetic joint infection. These 2 patients were treated with 2-stage reimplantations despite the MSIS data and had negative intraoperative cultures. Might organisms that were difficult to culture have been eradicated by the 2-stage revision? The MSIS criteria, although a brilliant contribution, are not the final word. Perhaps they were wrong. When should we order the synovial fluid alpha defensin? The current article includes an algorithm advising how to interpret the 4 permutations of synovial fluid alpha defensin and synovial fluid CRP. It does not explain when the test was indicated. This was a retrospective review of patients who had the test ordered by several physicians in varied circumstances. Future structured studies will be important. Should we order synovial fluid alpha defensin when the American Academy of Orthopaedic Surgeons guidelines indicate an aspiration (clinical suspicion or elevated erythrocyte sedimentation rate [ESR] and CRP)? If the synovial fluid is aspirated and if MSIS criteria define periprosthetic joint infection, then the cell count and differential are not yet likely to be replaced. Will the threshold values for synovial fluid alpha defensin and synovial fluid CRP prove to be more reliable than cell counts? Perhaps MSIS criteria need to be tested by long-term clinical studies. This would be challenging. If an MSIS-negative revision fails because of a periprosthetic joint infection, was that a new infection or a missed infection? In a 2017 lecture, “Prosthetic Joint Infection: A True Menace,” Dr. Parvizi made the point that even registry data must be regarded skeptically when it comes to infection5. Many cases reported as “aseptic” loosening are likely missed periprosthetic joint infection. Maybe arthroplasties are “all infected, all the time” and increased bacteria and the host ecology yield a periprosthetic joint infection? Maybe the immune system occasionally overresponds, producing alpha defensin prematurely as in metallosis? Perhaps certain bacteria multiply without provoking an immune response? If Mother Nature can be fooled, it is no surprise that our tests have limits too. It is a complicated game of numbers.

Synovial Fluid Alpha-Defensin Is an Adjunctive Tool in the Equivocal Diagnosis of Periprosthetic Joint Infection

BackgroundSynovial fluid alpha-defensin has shown to be a reliable diagnostic test for the diagnosis of periprosthetic joint infection (PJI), but its use in equivocal cases has yet to be established. The purpose of this study was to determine the reliability of alpha-defensin testing in patients, where the diagnosis of PJI was unclear. MethodsA consecutive series of 41 synovial aspirations by a single surgeon that were sent for alpha-defensin testing in equivocal cases of PJI were retrospectively reviewed. Indications for alpha-defensin testing included recent antibiotic use, borderline synovial fluid cell count, and differential, suspected culture-negative infection, and suspected false-positive culture. PJI was diagnosed using the Musculoskeletal Infection Society (MSIS) criteria. ResultsOf the 39 aspirations in 32 patients included in the study, there were 33 (85%) knee and 6 (15%) hip samples. Eleven (28%) samples met MSIS criteria for PJI. Of the 23 samples that had recent antibiotic use (6 MSIS positive, 17 negative), alpha-defensin results confirmed the correct MSIS diagnosis in 19 (83%) samples. Of the 11 samples in which alpha-defensin testing was performed for a borderline cell count (3 MSIS positive, 8 negative), alpha-defensin confirmed the MSIS diagnosis in 10 of 11 (91%) samples. Finally, among the 5 samples with suspected false-positive or false-negative cultures (2 MSIS positive, 3 negative), alpha-defensin confirmed the correct diagnosis in 3 (60%) samples. The overall sensitivity, specificity, negative predictive value, and positive predictive value of synovial alpha-defensin were 82%, 82%, 92%, and 64%, respectively. ConclusionIn patients for whom the diagnosis of PJI is unclear because of recent antibiotic use, equivocal laboratory findings, or suspected false-negative or false-positive cultures, synovial fluid alpha-defensin can provide an additional data point to assist the clinician in determining whether PJI is present but is prone to false-positive results in this challenging population.

Alpha-defensin-novel synovial fluid biomarker for the diagnosis of periprosthetic joint infection.

Periprosthetic joint infection (PJI) continues to be a significant complication after total joint arthroplasty. Diagnosis of PJI can be challenging and elusive in the absence of a gold standard. This purpose of this article is to review the current evidence on the utility of serum and synovial fluid biomarkers to help aid in the diagnosis of PJI with focusing on synovial fluid alpha-defensin. Articles and data for this review were identified by searches of PubMed and Ovid MEDLINE up to June 1, 2016. In addition, we manually reviewed the bibliographies of the retrieved articles for additional citations for references from relevant articles on the diagnosis of PJI. Serum biomarkers can be elevated in various inflammatory conditions. Synovial fluid biomarkers are more accurate for the diagnosis of PJI compared to serum biomarkers. Based on current available data, alpha-defensin is the most promising synovial fluid biomarker for the diagnosis of PJI and is commercially available. Synovial fluid alpha-defensin could enhance our ability to identify PJI and incorporate into the diagnostic algorithm in the future. Large-scale studies are needed to provide more data for its significance for the diagnosis of PJI.

The role of biomarkers in the diagnosis of periprosthetic joint infection.

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

When Is a Positive Culture in Shoulder Surgery Not an Infection? Commentary on an article by William R. Mook, MD, et al.: "The Incidence of Propionibacterium acnes in Open Shoulder Surgery. A Controlled Diagnostic Study".

Propionibacterium acnes represents the most common pathogen in periprosthetic joint infections of the shoulder, accounting for up to 70% of positive culture results at the time of revision surgery1. This diagnosis can be elusive for several reasons. P. acnes is a commensal organism of low virulence that populates the dermal sebaceous glands about the shoulder2. Its clinical presentation is often insidious and delayed and is frequently characterized clinically by persistent shoulder pain and a paucity of cutaneous, systemic, or radiographic signs. Furthermore, the preoperative work-up has been characterized historically by poor sensitivity. Acute-phase serologic markers such as the erythrocyte sedimentation rate and C-reactive protein level are often normal in P. acnes infections and the organism can be difficult to culture, requiring long-duration culture holds in multiple culture media3 for optimal culture yield. The usefulness of intraoperative frozen sections for aiding in the diagnosis of periprosthetic joint infections of the shoulder varies from one pathology laboratory to another, but has been inconsistent at best4. Because of the low virulence of P. acnes and the associated diagnostic delay and uncertainty, surgeons are often confronted with difficult treatment dilemmas at the time of revision surgery, such as determining whether or not a revision should be carried out in a staged fashion until a periprosthetic joint infection can be effectively ruled out. In addition, positive cultures at the time of revision surgery may represent a true periprosthetic joint infection but may also arise unexpectedly as a contaminant during specimen procurement and culture incubation. Mook et al. set out to determine the rate of positive culture growth from deep-tissue specimens obtained from patients undergoing open surgery of the glenohumeral joint as well as the demographic correlates of the culture results. One of the study strengths is …

The Alpha-defensin Test for Periprosthetic Joint Infection Responds to a Wide Spectrum of Organisms.

BackgroundThe alpha-defensin test has been previously demonstrated to be highly accurate in the diagnosis of prosthetic joint infection (PJI), nearly matching the Musculoskeletal Infection Society definition for PJI. However, the relationship between alpha-defensin levels and differing infecting organism has not yet been investigated.Questions/purposesThe purpose of this study is to describe the breadth of organisms that can trigger a positive synovial fluid alpha-defensin test result in the setting of PJI and also to assess the magnitude of the alpha-defensin result in terms of various pathogen characteristics.MethodsBetween December 2012 and March 2014, one laboratory processed 2319 synovial fluid samples for alpha-defensin testing. The present study reviewed the results of the 1937 samples that simultaneously had a synovial fluid culture performed; these came from 418 surgeons in 42 states. The overall culture-positive rate was 49% (244 of 498) among alpha-defensin-positive synovial fluids and 1% (19 of 1439) among alpha-defensin-negative synovial fluids. The organisms recovered from 244 alpha-defensin-positive, culture-positive fluids were recorded and grouped based on various characteristics, including Gram type, species, virulence, oral pathogenicity, and source joint. Alpha-defensin-negative samples served as uninfected controls. Median alpha-defensin levels were calculated for each group, and Dunn’s multiple comparison test for nonparametric data was used to identify any statistically significant (p < 0.05) organism-specific differences in the alpha-defensin level.ResultsThe alpha-defensin test for PJI was positive in the setting of a wide spectrum of organisms typically causing PJI. The median alpha-defensin level for all 244 alpha-defensin-positive, culture-positive samples (4.7 [interquartile range {IQR}, 3.7–5.3]) was higher than negative controls (0.26 [IQR, 0.22–0.33]) with a median difference of 4.4 (p < 0.001). There were no differences in the median alpha-defensin levels when performing a multiple comparison test among Gram-positive organisms (4.7 [IQR, 3.6–5.3]), Gram-negative organisms (4.8 [IQR, 4.2–5.3]), yeast (4.1 [IQR, 2.2–5.1]), virulent organisms (4.7 [IQR, 3.8–5.2]), less virulent organisms (4.8 [IQR, 3.6–5.4]), oral pathogens (4.5 [IQR, 3.2–5.2]), knees (4.7 [IQR, 3.7–5.3]), hips (4.9 [IQR, 4.1–5.8]), or shoulders (5.3 [IQR, 4.0–10.7]) with all comparisons having a p > 0.999.ConclusionsThe alpha-defensin test provides consistent results regardless of the organism type, Gram type, species, or virulence of the organism and should be seriously considered to be a standard diagnostic tool in the evaluation for PJI. Future research should focus on the performance of this test in specific clinical scenarios such as the immediate postoperative period in the setting of severe immunocompromise and in the setting of a native joint.Level of EvidenceLevel III, diagnostic study.