Meningococcal DNA detection by PCR (including Pneumococcal PCR)
The Meningococcal Reference Unit provides a separate manual that is distributed to all
users of the unit.
Collection container (including preservatives):
EDTA Blood tube
CE marked leak proof container
Specimen type: EDTA blood, CSF, pleural
Where a CSF sample is available, this should be sent in addition
to an EDTA blood sample
Collection: CE marked leak proof container
Specimen transport: Ambient or refrigerated
Specimen type and transport:
- EDTA blood sample collected on admission should be sent to the
Meningococcal Reference Unit (MRU) if PCR confirmation is required.
Heparinised, clotted blood, serum or citrated samples can be
tested, but EDTA is preferred.
- Whole CSF (i.e. an uncentrifuged specimen) should be sent in
small sterile containers such as a sterile 2mL screw capped vial
(rather than universal containers).
Minimum volume of sample: Minimum volume of
Special precautions: Remember to also collect
blood cultures and a throat swab for bacteriology and label these
clearly for meningococcal investigation.
Measurement units: Threshold Cycle (CT)
Biological reference units: Not applicable
Turn round time for provisional result (calendar
days): 1-2 days
Turn round time to final result (calendar
days): 3 days
Turnaround time: Same day (if received by
Results on specimens received up to 10.00am on Monday - Friday
are normally available between 4.30pm and 5.00pm on the same
Positive results will be telephoned following serogroup
confirmation up to 5.30pm, or as soon as possible on the morning of
the next working day, when printed reports will also be sent
Urgent turn-round times: Arrangements to accept
couriered urgent samples for PCR or other investigations
must be agreed with the MRU before the samples are
sent. Failure to do so may result in the specimen(s) not being
tested in a timely fashion.
Clinical decision points: Not applicable
Factors known to significantly affect the
results: Any specimens for PCR tests should be stored at
4°C and not frozen prior to transport.
The likelihood of a positive result decreases as the interval of
sampling after starting antibiotics lengthens. Samples for PCR
taken more than 48 hours after commencement of antibiotic therapy
are unlikely to give useful results. CSF may remain "positive" for