CSF Flashcards
How many CSF samples should be taken and why?
Best practice to take 3+ samples
3+ samples required for a serial red cell count
This might not always be possible, depends on how well the patient can tolerate it etc
Might get 5+ samples depending
Why do we do a serial red cell count
Gives us information on how traumatic a tap was
Red cells should be highest in the first sample but should decrease with each sample
What would high red blood cells in each sample indicate
Subarachnoid haemorrhage
Why would a random sample have an increased red cell count
Might be due to movement of the patient or movement of the needle etc
There might be high red cells in 2 or 3 of the samples if there was poor access etc
When do we a serial red cell count
Done on all samples as long as there is 3+ samples
If you have 6 CSF samples which ones do you use? Why?
Use the last three samples
i.e. the ones labelled 4, 5, 6
Least amount of red blood cell contamination
How do we process a CSF sample
Describe the appearance of all CSF samples
White cell count + Diff if necessary
Supplemental tests
How do we describe the appearance of CSF
Colourless
Blood stained
Xanthochromia
Spider-web clot
What does Xanthochromia mean?
Straw coloured CSF
Due to the breakdown of bilirubin
What does a spider web clot in a CSF indicate?
TB meningitis
What sample do we carry out a white cell count on? Why?
Last sample
Most accurate count, it’s directly from patient, least contamination
What is considered a high white cell count for CSF?
White cell counts of 5 or higher
What is considered a high red cell count?
Red cell count of 10 or higher
What would a CSF with a wcc >5 look like?
Cloudy in appearance
What can be done if the red blood cells are really high? Why
Use Turk’s solution
This dissolves any red blood cells
This allows for a more accurate white blood cell count
What do we do if a white blood cell count is greater than 5?
We carry out a differential stain
How do we carry out a differential stain?
Count the number of mononuclear cells versus polynuclear cells
What does high mononuclear cells in a CSF diff mean
Viral infection
What does high polymorphonuclear in a CSF diff mean?
Bacterial infection
Do we do gram stains for CSF?
No gram stains
We do a film array instead
Give some examples of internal supplemental test
Biochemistry for protein and glucose
Immunology for monoclonal bands
Give some examples of send outs
MS investigation -> send out to UK
Alzheimer’s investigation -> send out to UK
Xanthochromia -> samples sent to Beaumont in a dark tube or wrapped in tinfoil
Query CJD sent out to Beaumont
Beta-2-transferrin sent to UK
How are glucose and protein affected in bacterial vs viral infection?
Glucose decreased and protein increased during bacterial infection
Less of an impact seen during viral infection -> increased protein only
Why might we test for Beta-2-transferrin?
Used to test if a sample contains any CSF
Maybe a patient has a query CSF leakage -> want to confirm is CSF
Non done in house, sent to the UK
When do we culture CSF
Only done if cultures are wanted
-> bacterial meningitis
No need if viral meningitis etc
What do we culture CSF on
Chocolate and blood agar
When do we read CSF plates
Read twice
Once after 24 hours
Once after 48 hours
What discs do we put up on CSF plates?
No discs
If any colony grows its significant
Why might we not see any growth when we culture CSFs up
Patients are nearly always on antibiotics already
This is why we use the film array
What is the principle behind the film array?
Nested PCR
What are the benefits and disadvantages of using Film Array?
Useful for CSFs which are usually culture negative
Only downfall is that sensitivities cannot be done
What film array panels do we use
Two panels:
- Meningitis/Encephalitis panel
- Respiratory panel
When do we use the film array respiratory panel?
▪ Done for someone suffering from flu symptoms who is Covid negative and GeneXpert negative
▪ Not very common, only done to try and figure out what exactly the patient has
Panel containing covid and adenovirus etc
What do we do if the film array is unable to type the virus?
We send the sample to the NVRL for typing
What should we be looking for in CSF for HIV/Transplant patients
Cryptococcus
We do a cryptococcus antigen screen on all newly diagnoses HIV patients
What are the common causes of bacterial meningitis in adults
H. influenzae
S. pneumoniae
N. meningitidis
What is the most common cause of viral meningitis?
70% is enterovius
What are some different types of meningitis
Bacterial
Viral
Cryptococcal meningitis
TB meningitis -> very rare in Ireland
What are some common causes of meningitis in MMUH
S. pneumoniae
Haemophilus. influenzae
Neisseria species including N. gonorrhea
Enterovirus
Herpes caused meningitis
What would indicate a cryptococcal infection?
Large volume of CSF
6+ samples etc
What is the most common cause of meningitis in children?
Adenovirus
