Objectives: Effect of delayed analysis on CSF white blood cell (WBC) count and glucose has never been studied in neonates.
Design: Prospective cohort study.
Setting: Level III Newborn Unit.
Patients: Neonates undergoing lumbar puncture (LP) were enrolled after consent. CSF was analyzed at baseline (30 min) for protein, WBC and glucose; and from the same sample for WBC and glucose after a lag of 2 and 4 hrs post-LP. Those with traumatic/inadequate CSF were excluded. Subjects were classified in 3 groups (n=20 each) based on baseline WBC count: No WBC, 1-30 WBC and >30 WBC/μL. Analysis was by repeated-measures ANOVA.
Results: There was a significant decline in mean CSF glucose from baseline to 2 and 4 hrs [41.0±19 to 38.3±19 and 36.2±20 mg/dl respectively] and WBC count [36±45 to 28.6±38 and 23.8±34 cells/μL respectively] (both p<0.001). CSF glucose and WBC declined in all 3 groups (p<0.001). High baseline CSF WBC (p<0.001) and protein (p<0.001) was associated with a more rapid decline in the levels of CSF WBC, but not glucose. True CSF parameters could be predicted from 4-hr parameters: "Baseline glucose= 5.4 + 0.98(4-hr glucose)" [adjusted R2 97.2%, p<0.001] and "Baseline WBC= 1.3(4-hr WBC) + 0.05(protein)" [adjusted R2 98.8%, p<0.001]. In group 3, diagnosis of meningitis (based on pleocytosis) would be missed in 52.6 % and 78.9 % subjects at 2 and 4 hrs respectively.
Conclusions: CSF WBC count and glucose decrease significantly with time. Reliance on WBC counts of delayed samples can result in under-diagnosis.
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