C‐reactive protein and immature‐to‐total neutrophil ratio have no utility in guiding lumbar puncture in suspected neonatal sepsis

Meningitis may complicate neonatal sepsis, but there is scant evidence to inform the decision to perform a lumbar puncture (LP) and considerable variation in practice. We investigated whether inflammatory markers - C-reactive protein (CRP) and immature-to-total neutrophil ratio (ITR) - were predictive of meningitis or significant cerebrospinal fluid (CSF) pleocytosis and useful in guiding the decision to perform a LP.We studied all inpatients in a single tertiary neonatal unit who were <6 months of age who had a LP performed between March 2011 and October 2014. We categorised CSF results as follows: (i) culture-positive meningitis; (ii) probable culture-negative meningitis but meeting a priori criteria for significant CSF leucocytosis; or (iii) no evidence of meningitis. CRP and ITR obtained within 48 h of LP were analysed. We assessed the test performance of CRP and ITR by area under receiver operating characteristic curves.A total of 757 (male 471, 62.2%) infants were included. The median (interquartile range) gestational age was 38.4 weeks (30-40.3), and birthweight was 2940 g (1330-3560). Ten (1.3%) infants had culture-positive meningitis; 71 (9.4%) were classified as probable culture-negative meningitis and 676 (89.3%) as non-meningitis. The area under receiver operating characteristic curve for culture-positive and probable culture-negative meningitis was 0.43 for CRP (95% confidence interval 0.36-0.51) and 0.58 for ITR (0.51-0.65). At a CRP threshold of 30 mg/L, there was a positive likelihood ratio (LR) of 0.77 and a negative LR of 1.44.CRP and ITR perform poorly in identifying infants with confirmed or probable meningitis. The decision to perform an LP should be more focused on clinical grounds and/or a positive blood culture and less on inflammatory or haematological markers in isolation.