The Diagnostic Utility of Fast Tests for Detecting C-Reactive Protein in Synovial Fluid in Periprosthetic Joint Infections.

BACKGROUND: Despite the fact that many synovial fluid biomarkers have found application in the routine diagnosis of periprosthetic joint infection (PJI), this process still remains a challenge for orthopaedic surgeons. To simplify this process, fast point-of-care (POC) tests can be used during ambulatory visits and in operating room conditions. However, before such tests can be routinely used in clinical practice, they require validation. The purpose of the present study was to evaluate the diagnostic accuracy of different fast POC tests for detecting C-reactive protein (CRP) in synovial fluid for the diagnosis of PJI. METHODS: Synovial fluid samples were collected from 120 consecutive patients who underwent revision total joint arthroplasty (TJA). The patients were divided into 2 groups. The first group included 76 patients who underwent revision for reasons other than infection (the aseptic revision TJA [arTJA] group), and the second group included 44 patients who underwent revision because of periprosthetic joint infection (PJI). The diagnosis of infection was made according to the International Consensus Meeting (ICM) 2018 criteria. All patients were operatively treated at a single orthopaedic center from January 2022 to February 2023. Four fast CRP tests with different cutoff values (1 and 3 mg/L, ≥8 mg/L, ≥10 mg/L [cassette], ≥10 mg/L [strip]) were used off-label for synovial fluid testing. Tests were performed on the same synovial fluid samples, and the results of these tests were compared with those obtained with the laboratory method. RESULTS: The cassette test with a minimum cutoff value of ≥8 mg/L demonstrated the best accuracy for the diagnosis of chronic PJI, with a sensitivity and specificity of 90.9% and 90.8%, respectively. For the cassette test with a cutoff value of >3 mg/L, the sensitivity and specificity were 68.2% and 77.6%, respectively. For the tests with a minimum cutoff value of ≥10 mg/L, the sensitivity and specificity were 77.3% and 94.7%, respectively, for the cassette test and 77.3% and 96.1%, respectively, for the strip test. The laboratory method with the statistically calculated threshold (2.7 mg/L) revealed the highest AUC (area under the receiver operating characteristic curve) value (0.95), with 90.9% sensitivity and 94.7% specificity. CONCLUSIONS: The cassette POC test with the minimum cutoff value of ≥8 mg/L had very good accuracy for the diagnosis of chronic PJI. This test had comparable sensitivity and slightly lower specificity in comparison with the laboratory method with the calculated threshold of 2.7 mg/L. LEVEL OF EVIDENCE: Diagnostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Blood and synovial fluid calprotectin as biomarkers to diagnose chronic hip and knee periprosthetic joint infections.

AIMS: Calprotectin (CLP) is produced in neutrophils and monocytes and released into body fluids as a result of inflammation or infection. The aim of this study was to evaluate the utility of blood and synovial CLP in the diagnosis of chronic periprosthetic joint infection (PJI). METHODS: Blood and synovial fluid samples were collected prospectively from 195 patients undergoing primary or revision hip and knee arthroplasty. Patients were divided into five groups: 1) primary total hip and knee arthroplasty performed due to idiopathic osteoarthritis (OA; n = 60); 2) revision hip and knee arthroplasty performed due to aseptic failure of the implant (AR-TJR; n = 40); 3) patients with a confirmed diagnosis of chronic PJI awaiting surgery (n = 45); 4) patients who have finished the first stage of the PJI treatment with the use of cemented spacer and were qualified for replantation procedure (SR-TJR; n = 25), and 5) patients with rheumatoid arthritis undergoing primary total hip and knee arthroplasty (RA; n = 25). CLP concentrations were measured quantitatively in the blood and synovial fluid using an immunoturbidimetric assay. Additionally, blood and synovial CRP, blood interleukin-6 (IL-6), and ESR were measured, and a leucocyte esterase (LE) strip test was performed. RESULTS: Patients with PJI had higher CLP concentrations than those undergoing aseptic revision in blood (median PJI 2.14 mg/l (interquartile range (IQR) 1.37 to 3.56) vs AR-TJR 0.66 mg/l (IQR 0.3 to 0.83); p < 0.001) and synovial fluid samples (median PJI 20.46 mg/l (IQR 14.3 to 22.36) vs AR-TJR 0.7 mg/l (IQR 0.41 to 0.95); p < 0.001). With a cut-off value of 1.0 mg/l, blood CLP showed a sensitivity, specificity, positive predictive value, and negative predictive value of 93.3%, 87.5%, 89.4%, and 92.1%, respectively. For synovial fluid with a cut-off value of 1.5 mg/l, these were 95.6%, 95%, 95.5%, and 95%, respectively. CONCLUSION: This small study suggests that synovial and blood CLP are useful markers in chronic PJI diagnosis with similar or higher sensitivity and specificity than routinely used markers such as CRP, ESR, IL-6, and LE. CLP was not useful to differentiate patients with PJI from those with rheumatoid arthritis. Cite this article: Bone Joint J 2021;103-B(1):46-55.

A Retrospective Analysis of Bacteriological Studies of Surgical Site Infections in a Monoprofile, Multidepartmental Orthopedic Hospital.

BACKGROUND: Despite improvements in surgical techniques, aseptics and prevention of infections, hospital surgical site infections (SSI) still remain one of the main reasons for failure in therapeutic musculoskeletal surgery. This study aimed to conduct a retrospective analysis of microbiological examinations and determine pathogen sensitivity to antibiotics as the basis for selecting methods for preventing and treating complicating infections. MATERIAL AND METHODS: The study is a retrospective analysis of bacteriological tests performed in the departments of the Public Clinical Hospital of the Medical Centre of Postgraduate Education in Otwock. Importantly, our monoprofile hospital specialising in musculoskeletal pathology is a reference centre, admitting patients from the entire country. Often these are patients transferred from Intensive Care Units at other hospitals with internally infected local emergencies (infections with local, complex, multidrug resistant bacterial flora). Bacteriological mapping of the hospital covered the period from 2009 to 2013 to indicate so called "strategic departments" demonstrating the most complex multidrug-resistant bacterial flora. Surgical site infections were managed by surgery with targeted antibiotic therapy. RESULTS: Analysis of patients' profiles revealed that SSIs detected across hospital departments in SPSK CMKP in Otwock mostly came from other medical centers where patients were initially hospitalized. The Osteomyelitis Department and the Department of Pelvic Pathology and Traumatology were identified as "strategic departments". CONCLUSIONS: 1. The analysis indicated that methicillin-sensitive Staphylococcus aureus (MSSA) was the most common pathogen responsible for complicating infections in our hospital. 2. The percentage of bacterial resistance to methicillin signifi -cantly increased in patients with multi-organ injuries who had previously been hospitalized at other centres. 3. Credible prevention and diagnosis of inflammatory risk factors in the preoperative period was of key importance in reducing the percentage of complicating infections.

The effects of cooperation between orthopaedic surgeons and microbiologists on the effectiveness of diagnosis and treatment of septic hip joint loosening.

BACKGROUND: The objective of this study is to compare the results of microbiological examinations of two types of materials: specimens collected intraoperationally upon removal of prostheses following septic loosening and cultures from sonicated implants. The study was the effect of collaboration between the Clinic of Orthopedics of A. Gruca Hospital in Otwock and the Department of Microbiology in Lublin. MATERIAL AND METHODS: The study population consisted of 24 patients aged 39 to 84 years, average of 68 years, undergoing surgeries at the Department of Bone and Joint Inflammation, Clinic of Orthopedics of A. Gruca Hospital in Otwock in years 2010-2011. All patients were qualified for surgical treatment consisting of removal of hip prosthesis due to inflammation. Sixty percent of the group were women, while the remaining forty percent were men. The methodology of the study was based on intraoperational collection of material for microbiological examinations at the Department of Microbiology of A. Gruca Hospital. The study material was collected from 3 locations: femoral shank, hip acetabulum and gluteal muscle. Explanted implants were placed in sterile containers, frozen at -20°C and transported to the Department of Microbiology in Lublin. There, the implants were sonicated. RESULTS: The obtained results were consistent in both groups in 37% of cases. In 9 patients (37%), standard cultures were negative while the cultures of sonicated material were positive. In 16 patients (67%), the spectrum of perioperative and sequential antibiotic therapy included flora cultured by standard methods as well as flora obtained from sonicated implant cultures. In the remaining patients, cultures obtained from sonicated material were resistant to antibiotics used. CONCLUSIONS: Cultures of sonicated implant materials increase the chance for identification of microbes responsible for inflammation. Limitations of the method include the requirement to either examine the implant shortly after removal or freeze the implant in order to prevent secondary infections of the material.