Clinical significance and cut-off value of the infection of coagulase-negative staphylococcus obtained from cerebrospinal fluid specimens in neurosurgical patients

Abstract

Objective To study on the contribution and cut-off value of coagulase negative staphylococcus (CoNS) in laboratory tests of postoperative infection in neurosurgery and optimize the diagnostic criteria of infection. Methods It made a retrospective study of 650 cerebrospinal fluid (CSF) specimens from neurosurgical patients, who were infected CoNS in Beijing Tiantan Hospital affiliated to Capital Medical University during 2013-2015. The epidemiological data were collected and 8 routine clinical laboratory tests were performed. T test was used to compare the difference among the groups. By making receiver operating characteristic (ROC) curve, the area under the curve (AUC), cut-off value, sensitivity and specificity were obtained. Results A total of 19 756 CSF specimens were collected and 650 CoNS were isolated. The separation rate of CoNS was 3.3% which was the most frequently isolated bacteria. The differences of cerebrospinal fluid white blood cell count(3 598.6±1 884.3, 678.1±629.1, t=2.662, P=0.012), multinucleated cell ratio in cerebrospinal fluid(76.0±32.6, 46.8±29.9, t=9.593, P=0.001), cerebrospinal fluid glucose concentration(5.9±2.12, 6.2±1.92, t=-16.296, P=0.001) and cerebrospinal fluid glucose concentration/blood glucose concentration (0.3±0.16, 0.63±0.31, t=-11.968, P=0.000) among groups were statistically significant. The AUCs of cerebrospinal fluid white blood cell count, cerebrospinal fluid glucose and cerebrospinal fluid glucose/blood glucose were more than 0.8, and the sensitivities of the three indicators were more than 80.0%. In addition, the specificity of cerebrospinal fluid glucose concentration/blood glucose concentration was more than 0.9. Conclusions CoNS was the main pathogenic bacteria of neurosurgical infections in a hospital. Cerebrospinal fluid white blood cell count, cerebrospinal fluid glucose and the ratio of cerebrospinal fluid glucose and blood glucose could be used for auxiliary diagnosis of CoNS infections in neurosurgical patients.(Chin J Lab Med, 2017, 40: 707-710) Key words: Cerebrospinal fluid; Neurosurgical infection; Coagulase-negative staphylococcus; Receiver operating curve