Abstract
Aim
Diagnosis of periprosthetic joint infection (PJI) is challenging given the limitations of available diagnostic tests. Recently, several studies have shown a role of the long pentraxin PTX3 as a biomarker in inflammatory diseases and infections. This single-center prospective 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 metal-on-metal implant revision or 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 Student's 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. Youden's 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
One-hundred fifteen patients (M:F=49:66) with a mean age of 62 years (40–79) underwent revision of THA (n=99) or TKA (n=16). According with MSIS criteria, 18 cases were categorized as septic and 97 as aseptic revisions. The average synovial fluid concentration of PTX3 was significantly higher in patients with PJI compared to patients undergoing aseptic revision (24,3 ng/dL vs 3,64 ng/dL; P=0.002). There was no significant difference in terms of serum concentration of PTX3 between the two groups. Synovial fluid PTX3 demonstrated an AUC of 0.96 (95%IC 0.89–0.98) with Se 94%, Sp 90%, PPV 67%, NPV 100%, LR+ 9.4 and LR- 0.06 for a threshold value of 4.5 ng/dL. Serum PTX3 demonstrated an AUC of 0.70 (95%IC 0.51–0.87) with Se 72%, Sp 67%, PPV 30%, NPV 93%, LR+ 2.2 and LR- 0.42 for a threshold value of 4.5 ng/dL.
Conclusions
In patients undergoing revision surgery for painful THA or TKA, synovial PTX3 demonstrated a strong diagnostic ability for PJI. Synovial PTX3 could represent a more useful biomarker for detection of PJI compared with serum PTX3.
