BACKGROUND: Periprosthetic joint infection is a complication that is difficult to deal with after joint arthroplasty. Early diagnosis is the key to treatment. To find a fast response, high-sensitivity and high-specificity molecular biomarker can significantly optimize the diagnosis process of periprosthetic joint infection. 
OBJECTIVE: To monitor blood procalcitonin, interleukin-6 and lipopolysaccharide binding protein levels, to compare with blood leukocyte count and C-reactive protein levels, to identify above indexes, and to distinguish sensitivity and specificity of periprosthetic joint infection.
METHODS: A total of 81 patients with pain after arthroplasty who were treated in Affiliated Hospital of Jining Medical College from January 2008 to December 2013 were enrolled in this study. The repair surgery of all patients was divided into two stages. In the first stage, complete debridement and the installation of temporary occupancy device were conducted. After 3 months averagely, two-phase reconstruction was performed. At 1 day before surgery, venous blood was collected. Calcitonin, interleukin 6, lipopolysaccharide binding protein, leukocyte count and C- reactive protein levels were detected. During the operation, synovial membrane and sample of false envelope around the prosthesis were collected. Bacterial and histological examinations were performed. The sensitivity and specificity were calculated using receiver operating characteristic curve.
RESULTS AND CONCLUSION: One-way analysis of variance results showed that the receiver operating characteristic curve of lipopolysaccharide binding protein was bigger, 0.962; 95 confidence interval 0.924-1.000. Diagnostic value was optimal, and the critical value was 23.5 μg/L. These data suggested that when lipopolysaccharide binding protein exceeded 23.5 μg/L before surgery, periprosthetic joint infection would be identified. The receiver operating characteristic curve of C-reactive protein was 0.871. The receiver operating characteristic curve of leukocytes was close to 0.5. The diagnostic value of leukocyte count on periprosthetic joint infection was not great. These findings indicate that lipopolysaccharide binding protein has good application prospect in the diagnosis of periprosthetic joint infection after joint replacement, and shows high positive predictive rate and negative predictive rate of periprosthetic joint infection.