The Role Of Leukocyte Esterase Strip Test And Procalcitonin Measurement In The Diagnosis Of Periprosthetic Joint Infection

Section A:Leukocyte Esterase (LE) Strips TestObjective:To investigate the value of LE strip test in the diagnosis of periprosthetic joint infection (PJI) by comparing Leukocyte Esterase (LE) strip test with synovial WBC count and tissue histologic analysis,.Materials and Methods:From January 2015 to December 2015,103 patients who were going to undergo joint revision arthroplasty in our ward were enrolled in this trial. Among them,93 patients had sufficient synovial fluid to apply LE strips. One drop of synovial fluid was applied to the leukocyte esterase (LE) strip (AUTION Sticks 10PA arkray), and the result was observed after 2-3 minutes. If the color turned into dark violet, we recognized this as a positive result, while other colors were regarded as negative results. A centrifuge was used when the synovial fluid was mixed with blood before being applied to the LE strip. After this, surplus synovial were sent to clinical laboratory for other tests. However, only 63 patients had enough synovial fluid to undergo synovial WBC count. Three pieces of tissues were sent to pathology department for both frozen section and paraffin section analyses at the time of surgery. One or more specimen of the three observed greater than 5 neutrophils per high-power field in 5 high-power fields were recognized as positive. The results of LE strip were compared with the results of frozen section analysis and combined section analysis. MSIS standard of PJI was used as "gold standard", and the sensitivity, specificity, positive predictive value, negative predictive value and the 95% confidence interval were calculated.Results:According to MSIS standard,93 patients applied LE strips, which include 38 PJI and 55 aseptic cases had a sensitivity of 92.1% (95% CI,77.5%-97.9%), specificity of 96.4% (95% CI,86.4%-99.4%).63 patients undergone synovial WBC count, which include 29 PJI and 34 aseptic cases had a sensitivity of 93.1% (95% CI, 75.8%-98.8%), specificity of 97.1% (95% CI,82.9%-99.8%). For all 103 patients undergone histologic analysis,41 were diagnosed with PJI and 62 with aseptic cases. Single frozen section analysis had a sensitivity of (95% CI,73.0%-95.4%), specificity of 87.1% (95% CI,75.6%-93.9%). Combined section analysis (both frozen section and paraffin section) had a sensitivity of 95.1% (95% CI,82.2%-99.2%), specificity of 83.9%(95% CI,71.9%-91.6%).Conclusion:Using LE strip in the diagnosis of periprosthetic joint infection has a high sensitivity and specificity, which is a simple and cost-saving method. Though LE strip and synovial WBC count almost have the same sensitivity and specificity, LE strip is more feasible than synovial WBC count, due to it only need one drop of synovial fluid and can show the result immediately. In comparison with frozen section analysis, LE strip also has better sensitivity and specificity. Though the combined section analysis has a little higher sensitivity, it cannot get the result before the operation.Section B:Serum Procalcitonin (PCT)Objective:Since blood is easy to obtain, serum markers are important indicators especially for the patients with no synovial fluid. This study aims to investigate the value of serum Procalcitonin (PCT) in the diagnosis of periprosthetic joint infection (PJI).Materials and Methods:Eighty patients in our ward who were suspected with periprosthetic joint infection (PJI) after total joint arthroplasty were enrolled from September 2014 to June 2015. Every patient was proceeded serum test including WBC, ESR, CRP, IL-6 and PCT.80 patients were divided into two groups according to MSIS guideline.Results:There were 38 patients in PJI group and 42 patients in non-infection group. T test showed WBC, ESR, CRP, IL-6 had statistically significant difference between PJI group and non-infection group (P=0.000). However, PCT had no statistically significant difference between PJI group and non-infection group (P=0.397). ROC curve showed that IL-6, CRP and ESR had a high AUC value. AUCIL-6=0.915 (P=0.000), AUCCRP=0.911 (P=0.000), AUCESR=0.910 (P=0.000), while AUCWBC=0.771 (P=0.000), AUCPCT=0.509 (P=0.893).Conclusion:According to our study, ESR、CRP、IL-6 are good serum markers, while serum PCT is not recommended for using in the diagnosis of PJI.