Table 5 Overview of diagnostically relevant routine parameters in acute bacterial meningitis (BM) and frequency of “typical” and “atypical” changes depending on the bacterial pathogen

Cell count (CC) / μLμL

„typical "CC ≥1000: ca. 80%

Mean (SD): 7753 (14736)

CC 100–999: 14%

CC <  100: 7%

[16] Cave „apurulent BM": do not discontinue antibiotic treatment when CC is low, but CSF lactate or protein values are high!

S. pneumoniae

Median (IQR): 1842 (291–4419)

CC > 999: 75.8-78%

CC < 100: 17-19.3%

CC < 10: 5%

([17, 136]) (n = 153) [24];

N. meningitidis

Median (IQR): 5328 (1590–12.433)

CC > 999: 80-82%

CC 100–999: 6.5-11%;

CC < 100: 9-11.6%,

initial CSF normal: 1.7% (CC ≤5/μL, TP ≤0.50 g/l und Glucose ratio CSF / blood ≥0.40)

[68] (n = 258) [24];

L. monocytogenes

Median (IQR): 680 (291–1545)

CC < 100: 11%

[99] (n = 30 + 62)

H. influenzae b

Median (Min-Max): 1470 (0–11,400)

CC > 999: 92.9%;

CC 100-999: 7%

CC < 100: 0%

[14] (n = 11)

[24]

 B-streptococci

Median (Min-Max): 1230 (0-80,000)

CC „normal": 6%

[57] (n = 242)

 Newborn meningitis

CC ≤ 3: 10%

[54]

Differential Cell count

„typical "= granulocytic

S. pneumoniae

≤20% Granulocytes: 5.9%

[24]

N. meningitidis

≤20% Granulocytes: 8.2%

[24]

L. monocytogenes

< 50% Granulocytes: 26%

[99]

H. influenzae b

≤20% Granulocytes: 4.3%

[24]

 B-Streptococcus

Median (Min-Max): 87 (0-100) %

[57]

Total protein (TP) in mg/l

„typical "TP > 1000

Mean (SD): 4900 (4500)

[16]

S. pneumoniae

Median (IQR): 2700 mg/l (1400–5800)

[136]

N. meningitidis

Median (IQR): 4500 mg/l (2200–7000)

[68]

L. monocytogenes

Median (IQR): 2500 mg/l (1760–3650)

[99]

H. influenzae b

Median: 1800 mg/l

[14](n = 11)

 B streptococci

Median (Min-Max): 2480 mg/l (200-16,000)

[57]

 Newborn meningitis

TP < 400: 0%

TP 410-1200: 24%

TP >  1200: 76%,

[54]

Lactate (mmol/L)

„typical "Lactate ≥3.5 l

diverging reference ranges, recommended cut-off: 3.9 mmol/L (=35 mg/dl)

Man (SD): 16.51 (6.1)

Median (IQR): 9.9 (6.8-12.9) mmol/L

[1, 97, 152]

 DD bacterial versus viral meningitis

Lactate as sensitive differentiation criterion (Meta-analysis: [79, 152])

Sensitivity untreated BM: 98%

Sensitivity after preantibiosis: 49%

Cave: Lactate increase also found in status epilepticus, cerebral infarction, ICB, Tumor, Herpes encephalitis

[152]

Macroscopy / Gram staining

positive 63-72%

no preantibiosis: 63%

with preantibiosis: 62%

[24] (n = 667);

[130]

S. pneumoniae

positive: 85.2%

[24] (n = 162)

N. meningitidis

positive: 72.5-89%

[24] (n = 356) [68]; (n = 244)

L. monocytogenes

positive: 37%

[99]

H. influenzae b

positive: 83.3%

[24] (n = 72)

CSF culture

Positive no preantibiosis: 65.8-88%,

positive with preantibiosis: 61.4-70%

[24, 130]

S. pneumoniae

positive: 75-87%

[96] (n = 83) [24];

N. meningitidis

positive: 79.5%

[24]

H. influenzae b

positive: 50%

[24]

Blood culture

positive no preantibiosis: 66%

positive with preantibiosis: 48%

[16, 130]

S. pneumoniae

positive: 42.6-67%

[24, 96] (n = 76) [136]; (n = 186)

N. meningitidis

positive: 12.6 -57%

[24, 68] (n = 227)

L. monocytogenes

positive: 61%

[99]

H. influenzae b

positive: 50%

[24]

 Newborn meningitis

positive: 62%

[54] (n = 92)