Abstract:

Objective To establish and evaluate a discriminant model of coagulase-negative Staphylococcus （CNS） as pathogenic bacterium in blood culturing. Methods A total of 178 inpatients with blood culturing report of CNS were analyzed retrospectively from January 2013 to June 2015 in the First Affiliated Hospital with Nanjing Medical University. According to the related criterion,these inpatients were classified into 2 groups,pathogenic bacterium group （104 cases） and contaminating bacterium group （74 cases）. Before blood culturing,9 indices,including temperature（T）,white blood cell （WBC）count,neutrophil （NEU）ratio,C-reactive protein （CRP）,procalcitonin （PCT）,erythrocyte sedimentation rate （ESR）,glucose （GLU）,time of the first bottle reported to be positive （TTP） and the number of bottles reported to be positive （N）,were recorded. Results T,WBC count,NEU ratio,CRP,PCT,ESR and N in pathogenic bacterium group were higher than those in contaminating bacterium group,while GLU and TTP were lower （P<0.05）. For the areas under receiver operating characteristic （ROC） curve （AUC） for the diagnosis of CNS,those of TTP（0.870）,PCT（0.869） and NEU regression ratio（0.833） ranked the top 3. The regression model of CNS as pathogenic bacterium established through forward method consisted of T,PCT,TTP and NEU ratio,and AUC of the regression model was 0.959. When the cut-off value was 0.50,the sensitivity was 0.918,the specificity was 0.900,Youden index reached its maximum of 0.820,the diagnosis accuracy of the regression model was 92.0%,and the Kappa value in consistency analysis between the regression model diagnosis and clinical diagnosis was 0.827. Conclusions The regression model established with T,PCT,TTP and NEU ratio plays a role for diagnosing rapidly whether CNS is a pathogenic bacterium of blood stream infection or not and guiding the rational use of antibiotics.

Key words: Coagulase-negative Staphylococcus, Blood culturing, Discriminant, Regression model, Receiver operating characteristic curve