Leukocyte Esterase Estimation to Diagnose Cerebro-Spinal Fluid Leucocytosis in Neonates

The study evaluated neonatal cerebro-spinal fluid (CSF) leucocyte esterase (LE) estimation by reagent strips to diagnose CSF leucocytosis in situations where the CSF leucocyte count is delayed or unavailable.

This prospective diagnostic study had a cohort-selection design. CSF samples of neonates with clinical sepsis were analysed for LE by reagent strips, cytochemistry, gram stain and culture. CSF LE was measured on an ordinal scale from nil to large. Correlations of CSF LE with CSF leucocyte and neutrophil count were determined. CSF LE was compared versus CSF leucocytosis (defined a priori ≥ 25 leucocytes/μL) and versus CSF neutrophilia (defined a priori ≥ 15 neutrophils/μL) as the reference standard.

A total of 341 neonates were enrolled. CSF LE values correlated with leucocyte count (rho = 0.49, p < 0.001) and neutrophil count (rho = 0.44, p < 0.001). LE had a sensitivity (95% CI) of 63.5% (51.2, 74.1), specificity 90.7% (88.4, 92.6), LR+ (likelihood ratio) 6.79 (4.43, 9.98) and LR- 0.40 (0.28, 0.55) to diagnose CSF leucocytosis. When expressed as an ordinal variable, LE had an area under the receiver operator characteristic curve of 0.77 (95% CI: 0.69, 0.85; p < 0.001) to detect leucocytosis. With respect to all parameters, the diagnostic performance of CSF LE to detect neutrophilia was inferior to the detection of leucocytosis.

CSF leucocyte esterase estimation by reagent strips has a moderately high specificity and a good LR⁺ but, overall, does not have sufficiently robust diagnostic accuracy to substitute CSF leucocyte counts.