BCPS Microbiology
Changes to CSF Requesting and Processing
CSF microscopy is performed on all CSFs sent to microbiology. A review of the results of microscopy over the previous year has revealed that CSF white cell count (WCC) <10 correlated very strongly with all targets returning negative on BioFire (in-house PCR). The correlation was weaker in very young children <1yr.
We are therefore introducing an algorithm to limit BioFire PCR testing to those CSFs with >10 white cells in patients over 1yr. All CSFs received from patient <1yr will continue to get BioFire PCR testing independently of their WCC.
These changes will be implemented from 2nd March 2026
When e-requesting it is very important that details of diagnosis and symptoms are included. Patient with signs of encephalitis – seizures, confusion, neurological signs will continue to have routine BioFire PCR testing regardless of WCC and if negative will need a CSF viral PCR (a test referred to the reference laboratory) even with WCC <10.
There are two options on CSF microbiology e-requesting:
- CSF microscopy and culture (with BioFire PCR if white cells >10)
- CSF viral PCR – referred test with 72hrs turnaround at least – to be requested on patients with signs of encephalitis only (not just meningitis.)
Please don’t request CSF PCR thinking that it is BioFire PCR. The BioFire PCR test will now be algorithmic rather than requestable.
When sending the CSF samples in universal containers please refer to the CSF sample requirements and send samples taken in number order of collection: samples 1 and 3 to microbiology; sample 2 to biochemistry (sample 4 for CSF PCR if indicated due to encephalitis.)
Please ensure Microbiology is contacted once the sample has been taken to discuss urgent processing of the sample.
