The profile of ancillary laboratory tests in neonates with positive blood and/or cerebrospinal fluid cultures

Abstract

Background. Blood and cerebrospinal fluid (CSF) cultures are used as a gold standard to diagnose neonatal sepsis/meningitis. A challenge in their use is low yield, and limited availability, especially in low-resource settings.
Objective. To evaluate profiles of full blood count (FBC), C-reactive protein (CRP), and CSF cell count and protein in neonates with culture-proven sepsis/meningitis.

Methods. Neonates with positive blood and/or CSF cultures who had results for FBC, CRP, CSF cell count and protein performed within 24 - 48 hours of culture were enrolled. The proportion of neonates with abnormalities in these tests was calculated and comparisons among different types of pathogens was performed.
Results. A total of 942 isolates were cultured in blood and/or CSF. Organisms isolated were Gram-negative (GN) bacteria (62.0%), Gram-positive (GP) bacteria (23.4%) and Candida species (14.6%). Common abnormality in FBC was thrombocytopenia, which was observed in 30% of neonates with culture-proven sepsis. There was a higher proportion of neonates with thrombocytopenia among those infected with GN bacteria (39.9%) and Candida species (44.6%) compared with those infected with GP bacteria (15.1%; p<0.001). Leukopenia was relatively more common among neonates infected with GN bacteria than those infected with GP bacteria (20.8% v. 8.4%; p<0.001). More than two-thirds (70%) of neonates had high CRP (≥10 mg/L). Finally, less than a third of neonates (26.7%) with positive CSF cultures had abnormal CSF cell count (>20 cells/mm3) and 61.6% had high protein (>150 mg/dL).

Conclusion. Majority of neonates with positive blood or CSF cultures have normal FBC or CSF cell count; therefore, the absence of abnormalities in these parameters cannot be used solely to exclude sepsis. CRP appears to be the most useful test for diagnosing sepsis, as it is raised in 70% of patients with culture-proven sepsis.