title: Receiver operating characteristic curves for comparison of serial neutrophil band forms and C reactive protein in neonates at risk of infection.
abstract: The performance of indirect indices of infection in the newborn vary because of differences in techniques, including diagnostic cut off levels. We have compared serial neutrophil band cell counts with C reactive protein measured by rate nephelometry. The 'gold standard' was a positive culture and the performance of the tests was compared by the technique of receiver operating characteristics (ROC) as well as sensitivity and specificity. A total of 172 septic screens were performed in 56 patients. The operational diagnostic cut off values were: C reactive protein greater than 8 mg/l, immature:total neutrophil ratio (I:T ratio) greater than 0.2, and band count greater than 5%. Compared with the sensitivity of C reactive protein (71%), I:T ratio (34%) was significantly different but band count (69%) was not. The specificity of C reactive protein (72%) was better than band count (39%) but no better than I:T ratio (73%). ROC curves were constructed for all possible diagnostic cut off values of the tests and superior performance was demonstrated for C reactive protein compared with band count and I:T ratio. We conclude that C reactive protein is a useful early indicator of infection in neonates and that ROC curves permit comprehensive and graphic comparison between tests and the calculation of optimal diagnostic cut off values.
authors.affiliation: Regional Neonatal Intensive Care Unit, Liverpool Maternity Hospital.
authors.forename: G A
authors.initials: GA
authors.lastname: Russell
authors.forename: A
authors.initials: A
authors.lastname: Smyth
authors.forename: R W
authors.initials: RW
authors.lastname: Cooke
mesh_terms: D001419:Bacteria / Q000302:isolation & purification; D001424:Bacterial Infections / Q000097:blood / Q000453:epidemiology* / Q000382:microbiology; D002097:C-Reactive Protein / Q000032:analysis*; D016009:Chi-Square Distribution; D005189:False Positive Reactions; D006801:Humans; D007231:Infant, Newborn; D007958:Leukocyte Count / Q000379:methods; D009391:Nephelometry and Turbidimetry; D009504:Neutrophils / Q000166:cytology*; D012372:ROC Curve; D012307:Risk Factors
chemical_list: D002097:C-Reactive Protein