The value of lymphocyte count and percentage in predicting the early infection after knee arthroplasy
Objective To investigate the value of lymphocyte count and percentage in predicting early infection after knee joint ar-throplasy.Method A retrospective analysis was made of the age,gender,BMI,operative time,intraoperative blood loss and laboratory data(C-reactive protein,erythrocyte sedimentation rate,white blood cell count,neutrophil and lymphocyte count and percentage on preoperative and postoperative days 1 and 4)of 345 patients,including 27 cases of early postoperative infection group,no infection group in 318 cases,who underwent unilateral total knee arthroplasty in our hospital from December 2018 to December 2022.The opera-tive time,age,gender,BMI,intraoperative blood loss and the difference in preoperative and postoperative hemoglobin between the two groups were recorded.Use SPSS statistical software was used to process the data.After selecting indexes with statistical differences,Pearson's correlation coefficient was used for correlation test to determine which markers were irrelevant to surgical factors(operation time and intraoperative blood loss).Finally,use Stata software to calculate the area under the ROC curve,95%CI,and p-value,and obtain the diagnostic threshold,sensitivity,and specificity of the selected biomarkers.Results There was no statistically significant difference between two groups in surgical age,gender,BMI,operative time,intraoperative blood loss,preoperative and postoperative hemoglobin difference,and laboratory markers before surgery(all P>0.05).There were statistically significant differences in CRP lev-el,neutrophil count and percentage at 4 days after surgery,lymphocyte count and percentage 1 and at 4 days after surgery between the two groups(P<0.05).Pearsons correlational test found that in the non-infected group,markers unrelated to surgical factors(operation time,intraoperative blood loss)were lymphocyte count and percentage 4 days after operation.We used the ROC curve of the stata soft-ware to determine the appropriate diagnostic threshold for the percentage of lymphocytes and their count at 4 days after early infection after knee replacement.The area under the ROC curve(AUC)of the lymphocyte percentage at 4 days after the operation was 0.755[95%CI(0.528,0.918),P=0.28].The optimal prediction threshold value of the lymphocyte percentage calculated based on the Youden index was<20.0%.The sensitivity and specificity of the diagnostic test were 91.67%and 55.57%respectively.The area un-der the ROC curve of the lymphocyte count at 4 days after the operation was 0.833[95%CI(0.637,0.970),P=0.28],and the threshold value for the best prediction of lymphocyte count based on the Youden index was<1 500/μl.The sensitivity and specificity of the diagnostic test were 91.67%and 66.67%respectively.Conclusion Lymphocyte percentage and lymphocyte count at 4 days post-operatively are reliable predictors of early infection after knee arthroplasty.Because of its high sensitivity,it can prompt early infection after knee arthroplasty.
Infection after total knee arthroplastyLaboratory markersLymphocyte count and proportionEarly infection
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NSTL
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