The relationship of C-reactive protein/interleukin-6 concentrations between serum and synovial fluid in the diagnosis of periprosthetic joint infection.

BACKGROUND: The relationship of C-reactive protein (CRP)/interleukin-6 (IL-6) concentrations between serum and synovial fluid and whether synovial CRP/IL-6 testing in addition to serum CRP/IL-6 testing would result in a benefit in the diagnosis of periprosthetic joint infection (PJI) deserves to be investigated. METHODS: From June 2016 to July 2019, 139 patients were included in the study. Synovial CRP and IL-6 were tested by ELISA. The serum CRP and IL-6 were obtained from medical records. The definition of PJI was based on the modified Musculoskeletal Infection Society (MSIS) criteria. The relationship of serum and synovial CRP and IL-6 and the value of each index in the diagnosis of PJI were evaluated. RESULTS: The receiver operating characteristic (ROC) curves showed that synovial IL-6 had the highest area under the curve (AUC) at 0.935, which was followed by synovial CRP, serum IL-6 and serum CRP 0.861, 0.847 and 0.821, respectively. When combining serum CRP and synovial CRP to diagnose PJI, the AUC was 0.849, which was slightly higher than the result obtained when using serum CRP alone. In contrast, when combining serum IL-6 and synovial IL-6 to diagnose PJI, the AUC increased to 0.940, which was significantly higher than that obtained using serum IL-6 alone. CONCLUSION: The synovial IL-6 has the highest diagnostic accuracy for PJI. However, inferring the level of CRP/IL-6 in the synovial fluid from the serum level of CRP/IL-6 was not feasible. Synovial CRP testing did not offer an advantage when combined with an existing serum CRP result to diagnose PJI, while additional synovial IL-6 was worthy of testing even if there was an existing serum IL-6 result.

Leukocyte esterase test and alpha-defensin test have similar accuracy for the diagnosis of periprosthetic joint infection.

BACKGROUND: The diagnosis of periprosthetic joint infection (PJI) after total joint replacement remains challenging. Synovial biomarkers are recommended as the major diagnostic criteria for PJI. The purpose of this study was to test the accuracy of the alpha-defensin test and compare it with that of the leukocyte esterase (LE) test for the diagnosis of PJI. METHODS: We obtained 130 hip or knee aspirates from May 2015 to September 2018. PJI was defined according to the European Bone and Joint Infection Society (EBJIS) criteria. Synovial fluid samples were tested with the alpha-defensin ELISA and a LE strip. For the LE strip test, besides using the traditional threshold 500 (equal to ++), we are also using an improved one, with 500 (equal to ++) serving as the threshold for the tests before centrifugation and both 250 and 500 indicating positive results after centrifugation. The receiver operating characteristic (ROC) curves, sensitivity, specificity, positive predictive value, negative predictive value, and Cohen's Kappa value were calculated for the LE and alpha-defensin tests. RESULTS: The area under the curve (AUC) of alpha-defensin, LE strip test with traditional, and improved interpretation strategy were 0.875, 0.854, and 0.877, respectively. The Cohen's Kappa value for the alpha-defensin tests was 0.826 with the traditional LE interpretation strategy and 0.875 with the improved strategy. CONCLUSION: The present study shows that the use of the LE strip to test synovial fluid yielded an accuracy similar to that of the alpha-defensin immunoassay for the diagnosis of PJI; this finding supports the 2018 ICM PJI definition, which considers positive alpha-defensin and LE test results to be equivalent.

Neutrophil to lymphocyte ratio as a predictor for diagnosis of early Periprosthetic joint infection.

BACKGROUND: Periprosthetic joint infection (PJI) is a catastrophic complication after total knee or hip arthroplasty. The diagnosis of PJI is very difficult, especially in the early postoperative period. The value of the neutrophil to lymphocyte ratio (NLR) is useful for diagnosing infectious diseases. The objective of this study was to investigate the accuracy of the NLR for the diagnosis of early PJI after total knee or hip arthroplasty. METHODS: We retrospectively evaluated consecutive primary total knee or hip arthroplasty and identified the patients who readmitted within the first 90 days postoperatively between January 2011 and October 2018.There were 20 cases diagnosed early PJI and 101 uninfected cases on the basis of the modified Musculoskeletal Infection Society (MSIS) criteria. The serum parameters including C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), white blood-cell (WBC) count, NLR and interleukin-6 (IL-6) were compared between the two groups. Receiver operating characteristic curves were generated to estimate the optimal cutoff values for each parameter. The sensitivity, specificity, positive predictive value and negative predictive value for each parameter were calculated. RESULTS: The CRP, ESR, WBC, NLR and IL-6 values were all significally higher in the infected group than the uninfected group. The median of CRP was 66.6 mg/l in the infected group and 8.6 mg/l in the uninfected group (p < 0.001). The median of ESR was 34.8 mm/hr. in the infected group and 17.4 mm/hr. in the uninfected group (p < 0.001). In the infected group and uninfected group, the median of WBC was 8.2X109 /L and 6.1 X109 /L (p = 0.002), respectively; while the median of NLR was 5.2 and 2.1 (p < 0.001). The median of IL-6 was 46 pg/ml and 6.4 pg/ml (p < 0.001),respectively. The best parameter for the diagnosis of early PJI was IL-6 (AUC = 0.814) followed by the NLR (AUC =0.802), CRP (AUC =0.793), ESR (AUC =0.744) and WBC (AUC = 0.632). CONCLUSIONS: This study is the first to show that NLR values are more accurate than CRP and may be considered as useful parameters for the diagnosis of early PJI because it is a cheap and convenient parameter to be calculated in daily practice without extra costs.

Plasma Fibrinogen Exhibits Better Performance Than Plasma D-Dimer in the Diagnosis of Periprosthetic Joint Infection: A Multicenter Retrospective Study.

BACKGROUND: The search for potential markers for a timely and accurate diagnosis of periprosthetic joint infection (PJI) is ongoing. Previous studies have focused on inflammatory markers and have rarely examined coagulation-related indicators. The purpose of this study was to evaluate the values of plasma fibrinogen, D-dimer, and other blood markers for the diagnosis of PJI through a multicenter retrospective study. METHODS: A total of 565 revision total hip and knee arthroplasty cases were enrolled in this study from January 2016 through December 2017, 126 of which had coagulation-related comorbidities and were analyzed separately. The remaining 439 cases included 76 PJI and 363 non-PJI patients. The definition of PJI was based on the International Consensus Meeting (ICM) on Periprosthetic Infection criteria. The diagnostic values of D-dimer, plasma fibrinogen, the erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) level, and white blood-cell (WBC) count were analyzed using receiver operating characteristic (ROC) curves. RESULTS: ROC curves showed that plasma fibrinogen had the highest area under the curve (AUC), 0.852, followed by 2 classical markers, the CRP level and ESR, which had an AUC of 0.810 and 0.808, respectively. D-dimer had an AUC of 0.657, which was the second lowest value and only slightly higher than that of the WBC count, 0.590. The optimal threshold for plasma D-dimer was 1.25 µg/mL, with a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 0.645, 0.650, 0.278, and 0.897, respectively. The optimal threshold for plasma fibrinogen was 4.01 g/L, which showed good sensitivity, specificity, PPV, and NPV, with values of 0.763, 0.862, 0.537, and 0.946, respectively. CONCLUSIONS: Plasma D-dimer may have a very limited diagnostic value for PJI, while plasma fibrinogen, another coagulation-related indicator, exhibits promising performance. Plasma fibrinogen has good sensitivity and specificity for diagnosing PJI, with values similar to those of classical markers, including CRP level and ESR. LEVEL OF EVIDENCE: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.