PENTRAXIN-RELATED PROTEIN PTX3 AS A NEW BIOMARKER FOR THE DIAGNOSIS OF PERIPROSTHETIC JOINT INFECTION: A SINGLE-CENTRE PILOT STUDY

Aim Diagnosis of periprosthetic joint infection (PJI) is still challenging due to limitations of available diagnostic tests. Many efforts are ongoing to find out novel methods for PJI diagnosis. Recently, several studies have shown a role of the long pentraxin PTX3 as a biomarker in inflammatory diseases and infections. This pilot diagnostic study evaluated the diagnostic ability of synovial fluid and serum PTX3 for the infection of total hip arthroplasty (THA) and total knee arthroplasty (TKA). Method Consecutive patients undergoing revision surgery for painful THA or TKA were enrolled. Patients with antibiotic therapy suspended for less than 2 weeks prior to surgery and patients eligible for spacer removal and prosthesis re-implantation were excluded. Quantitative assessment of synovial fluid and serum PTX3 was performed with ELISA method. Musculoskeletal Infection Society (MSIS) criteria were used as reference standard for diagnosis of PJI. Continuous data values were compared for statistical significance with univariate unpaired, 2-tailed Student9s t-tests. Receiver operating characteristic (ROC) curve analyses was performed to assess the ability of serum and synovial fluid PTX3 concentration to determine the presence of PJI. Youden9s J statistic was used to determine optimum threshold values for the diagnosis of infection. Sensitivity (Se), specificity (Sp), positive (PPV) and negative (NPV) predictive values, positive (LR+) and negative (LR-) likelihood ratio, area under the ROC curve (AUC) were calculated. Results Sixty-two patients (M:F=28:34) with a mean age of 64 years (40–78) underwent revision of THA (n=52) or TKA (n=10). According with MSIS criteria, 10 cases were categorized as septic and 52 as aseptic revisions. The average synovial fluid concentration of PTX3 was significantly higher in patients with PJI compared to patients undergoing aseptic revision (23,56 ng/mL vs 3,71 ng/mL; P=0.0074). There was no significant difference in terms of serum concentration of PTX3 between the two groups. Synovial fluid PTX3 demonstrated an AUC of 0.93 (95%IC 0.86–0.97) with Se 100%, Sp 85%, PPV 55%, NPV 100%, LR+ 6.6 and LR- Conclusions Synovial PTX3 demonstrated a strong diagnostic ability for PJI. PTX3 could represent a useful biomarker for detection of PJI in patients undergoing revision surgery for painful THA or TKA. Larger diagnostic studies are required to confirm these preliminary data.