Abstract
OBJECTIVE: To explore the diagnostic efficacy of electrochemical detection of synovial fluid leukocyte esterase (LE) based on glucosyl ester for periprosthetic joint infection (PJI) in rabbits. METHODS: The enzyme kinetic parameters of the LE-catalyzed reaction based on glucosyl esters were determined electrochemically, and the charge-LE concentration relationship was plotted. Forty-eight healthy New Zealand rabbits were randomly divided into a sham-operation group (blank group), a knee joint metal prosthesis implantation group (control group), and a knee joint metal prosthesis implantation with PJI group (experimental group), with 16 rabbits in each group. The experimental group underwent intra-articular injection of 1×10 (5) CFU/mL Staphylococcus aureus suspension at 7 days after right knee joint prosthesis implantation. The control group underwent intra-articular injection of 1 mL of sterile saline at 7 days after right knee joint prosthesis implantation. The blank group underwent right knee joint capsule incision and suture, followed by intra-articular injection of 1 mL of sterile saline 7 days later. The general condition of the animals was observed after operation. At 28 days after operation, imaging examination, microbiological examination, hematological test, and electrochemical detection of synovial fluid LE were performed. The area (AUC) under the receiver operating characteristic curve (ROC) was used to evaluate the sensitivity and specificity of LE-based detection of PJI. RESULTS: The Michaelis constant of the enzymatic reaction of LE catalyzing glucosyl ester was 7.335 mmol/L, and the maximum reaction rate of the enzymatic reaction was 63.750 μmol·L (-1)·min (-1). The calibration curve regression equation for the charge difference (ΔQ)-LE concentration was C ((LE))=0.7115ΔQ-14.75, with a determination coefficient R (2) of 0.988 4 (95% CI: 0.5698, 0.8532, P<0.001). All animals survived to the end of the experiment. During the period, the experimental group showed signs of joint infection, and the microbiological test results were all positive. The other two groups had no related infection manifestations and the tests were negative. Imaging examination showed that the experimental prosthesis was stable in position, soft tissue swelling around the joint and mild deformation in the joint. There was no obvious swelling in the soft tissue around the joints in the other two groups, and the joints were in good alignment. Synovial fluid and hematological tests revealed that the experimental group exhibited significantly higher levels of LE, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), white blood cell count (WBC), neutrophil count (Neu), and monocytes count (Mon) compared to both the control group and the blank group ( P<0.05). Notably, ESR and Mon levels were significantly higher in the control group compared to the blank group ( P<0.05). The mentioned indicators, with an AUC>0.9 ( P<0.05), possess good diagnostic value for PJI. Among them, CPR and Neu exhibit the highest sensitivity, reaching 93.8%, while LE, ESR, and Mon demonstrate the highest specificity, reaching 100%. CONCLUSION: Both synovial fluid LE and hematological testing exhibit good diagnostic efficacy in the rabbit PJI model, with the method based on electrochemical quantitative detection of glucose-based esters for LE demonstrating higher specificity, sensitivity, and accuracy.