Time to positivity in differential diagnosis of intracranial infection caused by coagulase-negative Staphylococcus

Abstract

Objective To evaluate the application of time to positivity (TTP) in differential diagnosis of intracranial infection caused by coagulase-negative Staphylococcus (CNS). Methods One hundred and twenty-four adult patients with positive CNS isolated from cerebrospinal fluid (CSF) including 70 cases with intracranial infection and 54 cases of CSF contamination, who were admitted in Xiangya Hospital of Central South University during January to December 2015, were retrospectively analyzed. The difference of TTP between two groups was compared, receiver operating characteristic (ROC) curve was analyzed and the area under the ROC curve (AUC) was calculated. The application of TTP in differential diagnosis of CNS infection was evaluated. SPSS 18.0 software was used to analyze the data. Results TTP in intracranial infection group was shorter than that in CSF contamination group [(23.5±7.5)h vs. (37.6±10.5) h, t=-8.717, P=0.000]. The AUC of TTP was 0.854. Taking the cut-off value of 27.94 h, the sensitivity, specificity, positive and negative predictive values in differentiation of two groups were 72.7%, 91.4%, 90.0% and 72.2%, respectively. There were statistically differences in TTP of Staphylococcus epidermidis, Staphylococcus haemolyticus and Staphylococcus capitis between two groups (Z=-4.496, -2.322 and -2.399, respectively, P<0.05 or <0.01). Conclusion TTP can be used to discriminate early intracranial infection and CSF contamination caused by CNS, and also can identify intracranial infection caused by different categories of CNS. Key words: Cerebrospinal fluid; Coagulase; Staphylococcus; Time to positivity; Intracranial infection