Table 3: Lumbar puncture findings1 [3, 9].

CSF findingNormal2ViralBacterialPartially treated bacterial

White cell count (cells/mm3)<5<1000>1000>1000
PMNs020–40%>85–90%>80%
Protein (mg/dL)<40Normal or <100>100–20060–100+
Glucose (mmol/L)≥2.5Normal Undetectable–<2.2<2.2
Blood to glucose ratio≥0.6Normal<0.4<0.4
Positive gram stain75–90% (depending on organism)55–70%
Positive culture>70–85%<85%

1Other investigations may also be performed on CSF to exclude nonbacterial causes of meningitis depending on the clinical scenario; including India Ink staining or antigen testing for Cryptococcus neoformans, Herpes simplex virus (HSV), cytomegalovirus (CMV) and enterovirus PCR.
2 Values for paediatric patients >1 month of age; some values vary for neonates [16].
Neonates: white cell count may be higher (<20 in the form of lymphocytes); normally zero PMNs, however some studies have found up to 5% PMNs in neonates without meningitis.
Neonates: normal protein <100 mg/dL.