Lab Case 20 – Interpretation

CSF features of bacterial infection present:

cloudy macroscopically

high WCC and predominant PMN

Gram negative diplococci

This indicates a  potential life threatening Meningococcal meningitis requiring early broad spectrum antibiotics, dexamethasone and resuscitation

Confounders – high red cell count, some mononuclear cells

RBC:WCC = 30:1 – very low and indicates a relatively high WCC

2. What common tests can you request on CSF?

  • gram stain
  • microscopy
  • culture
  • xanthochromia
  • WCC
  • RCC
  • protein
  • oligoclonal bands
  • extended culture
  • cryptoccal antigen and Indian ink stain
  • ZN stain for acid fast bacilli
  • PCR for enterovirus and HSV
  • cytology

3. What is the normal ratio of red cells to WCC in CSF?

500:1 (may vary depending on peripheral RBC count)

4. What is the role of steroids?

Corticosteroid use in Western countries is supported by evidence from a randomised controlled trial performed in Europe:

The points to note about this trial are:

  • dexamethasone 10mg QID for 4 days led to a decrease in death and disability in adults treated for bacterial meningitis
  • dexamethasone was administered 10-15 minutes before or at the time of antibiotics (no-one knows if there is benefit in administering steroids in any way other than this and there may be harm)
  • the benefit was only demonstrated in patients with pneumococcal meningitis in a setting where resistant pneumococcus was rare (no benefit has been demonstrated in meningococcal meningitis)

Two studies from third world countries have failed to demonstrate a benefit: