Wert der 16S rDNA Polymerase-Ketten-Reaktion (PCR) zur intraoperativen Infektdetektion bei Endoprothesenrevisionseingriffen

Preoperative PCR analysis of synovial fluid has limited value for the diagnosis of periprosthetic joint infections of total knee arthroplasties

Preoperative diagnosis of periprosthetic joint infection (PJI) is important because of the therapeutic consequences. This prospective study was designed to answer the question, if preoperative PCR analysis of the synovial fluid in addition to the culture and the CRP analysis of the blood are helpful for the diagnosis of PJI in knee arthroplasties. Before revision CRP analysis of the blood, cultivation and PCR analysis of synovial fluid of 116 knee endoprostheses were performed. During revision surgery, five tissue samples of the periprosthetic tissue were cultured and five further samples subjected to histological analysis. These analyses of the periprosthetic tissue were used to verify the results of the preoperative diagnostic methods. Twenty-seven prostheses were identified as infected (prevalence 23.3%). The combined analyses of the joint fluid cultivation and the CRP blood level resulted in a sensitivity of 77.8%, a specificity of 95.5%, a positive-predictive value of 84.0%, a negative-predictive value of 93.4% and an accuracy of 91.4%. The PCR analysis of the synovial fluid resulted in a sensitivity of 55.6%, a specificity of 82.0%, a positive-predictive value of 48.4%, a negative-predictive value of 85.9% and an accuracy of 75.9%. The sensitivity for culture of the aspirate and PCR analysis in combination with an elevated CRP level was 85.2%, the specificity 82.0%, the positive-predictive value 58.9%, the negative-predictive value 94.8% and the accuracy 82.7%. The preoperative PCR analysis of synovial fluid has only limited value in addition to the standard culture analysis.

Detection of Bacteria Bearing Resistant Biofilm Forms, by Using the Universal and Specific PCR is Still Unhelpful in the Diagnosis of Periprosthetic Joint Infections

Intraoperative conventional bacteriological cultures were compared with different polymerase chain reaction (PCR) methods in patients with total joint arthroplasties. The isolated bacteria were investigated for biofilm formation, and the biofilm forming strains, in their planktonic and biofilm forms, were further tested for their antimicrobial resistance against several clinically important antimicrobials. Forty four bone and joint samples were included and classified as infected or non-infected according to standard criteria for periprosthetic hip and knee infections. For the bacteriological diagnosis, conventional culture, two types of universal PCR and species specific PCR for three selected pathogens (Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa) were applied. Biofilm formation determination was performed by the tissue culture plate method. Antimicrobial susceptibility of the planktonic bacteria was performed by the minimal inhibitory concentration determination and, of the biofilm forms, by the minimal inhibitory concentration for bacterial regrowth from the biofilm. Twenty samples were culture positive, with S. epidermidis, S. aureus, or P. aeruginosa. All PCR methods were very ineffective in detecting only one pathogen. All isolates were biofilm positive and their biofilm forms, were highly resistant. In this study, compared to PCR, culture remains the "gold standard." The biofilm formation by the causative bacteria and the concomitant manifold increased antimicrobial resistance may explain the clinical failure of treatment in some cases and should be considered in the future for therapeutic planning.

The use of receiver operating characteristics analysis in determining erythrocyte sedimentation rate and C-reactive protein levels in diagnosing periprosthetic infection prior to revision total hip arthroplasty

BACKGROUND

Periprosthetic infection (PPI) is a difficult complication in total joint arthroplasty, and while erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are acute phase reactants thought to be of high predictive value for diagnosing infection, no clear cut-off values have been defined. The current study aimed to determine the cut-off values for ESR and CRP that improve clinical differentiation between aseptic failure and PPI in total hip arthroplasty (THA).

METHODS

Four hundred and seventy-nine patients who underwent revision THA for either aseptic mechanical failure or PPI during the period of 2000 to 2005 were included in the study. Specific exclusion criteria were applied to eliminate inflammatory or other confounding conditions. All patients underwent preoperative testing of ESR and CRP. Receiver operating characteristic (ROC) curves were constructed to determine maximum sensitivity and specificity.

RESULTS

Patients with PPI had significantly higher ESR and CRP values compared to patients undergoing revision for aseptic etiologies. An ESR threshold of 30 mm/h gave a sensitivity of 94.3% and a CRP threshold of 10 mg/l gave a sensitivity of 91.1%. Combining both ESR and CRP cut-offs for a positive diagnosis increased the sensitivity to 97.6%. However, when calculated by ROC analysis, the predictive cut-offs equated to 31 mm/h for ESR and 20.5 mg/l for CRP.

CONCLUSIONS

The gold standard for diagnosing PPI remains bacterial culture, but sensitivity is negatively affected by prior antibiotic exposure, strongly adherent bacteria, slow growing persisters, and biofilms. ESR and CRP are reflective of systemic changes in infection and pose an attractive, less invasive alternative with reasonable sensitivity and specificity. The current study is the first to identify ideal cut-off values for ESR and CRP in THA patients, providing an optimum balance between sensitivity and specificity based on ROC curves.

[Diagnostic strategies in cases of suspected periprosthetic infection of the knee. A review of the literature and current recommendations]

Reliable confirmation of periprosthetic infection after total knee arthroplasty is a diagnostic challenge. The present work reviews published data evaluating the available diagnostic tools. Erythrocyte sedimentation rate and C-reactive protein serum levels are relatively sensitive methods with rather low specificity towards periprosthetic infection and are mainly applied to exclude infection. Studies evaluating scintigraphic methods--especially white cell scans--provide inconsistent data with varying accuracy. Consequently, white cell scans cannot be recommended as standard methods. Immunoscintigraphy with antigranulocyte antibodies and FDG-PET scans demonstrated promising results with particularly high sensitivities, but have to be validated in larger studies. Microbiological evaluation of joint aspirates proved high specificity for periprosthetic infection. However, an average of 20% of infected cases remained undetected. Nevertheless, aspiration is widely recommended for preoperative isolation of the infecting organism. Intraoperative frozen sections demonstrated excellent specificity with good sensitivity. The real accuracy of intraoperative culture and permanent histology cannot be determined due to the missing golden standard; however, a combination of both methods is recommended to define the final diagnosis. Large studies validating both methods and criteria for the final diagnosis of periprosthetic infection are necessary to optimize the diagnostic algorithm.