Paper II — 2022 July (Supplementary) (2019 Scheme) — Q12
4 min read
Paper II
2022 July (Supplementary) (2019 Scheme) · 100 marks · 180 min
Question
A CSF sample, collected in the ward by lumbar puncture, does not reach the laboratory
for processing for bacterial culture. Discuss the correct decision and the appropriate
action to be taken.
Q124 marksShort Answers
Answer
The correct decision is that this CSF sample is unacceptable for standard processing under the usual protocol, and the situation must be handled urgently given the clinical gravity of suspected bacterial meningitis.
Appropriate action:
CSF is a precious, often irreplaceable specimen (obtained via an invasive procedure), and unlike urine or sputum, a repeat sample cannot simply be requested without another lumbar puncture — so the sample should not be automatically discarded; instead, the delay and its implications must be carefully assessed.
Process the sample as soon as it arrives, but interpret and report the results with the delay explicitly documented and communicated to the clinician — since fastidious organisms commonly implicated in bacterial meningitis (e.g., Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae) are highly susceptible to autolysis/death outside the body, and prolonged delay before culture (ideally CSF should be processed within 1 hour, or refrigeration/appropriate transport considered if any delay is anticipated) significantly reduces culture yield and increases the risk of a false-negative result.
Communicate promptly with the requesting clinician, informing them of the delay and its potential impact on test sensitivity, so that clinical decision-making (e.g., continuing empirical antibiotics) is not solely reliant on a negative culture result in this circumstance.
Given that antibiotic treatment for suspected bacterial meningitis should never be delayed pending laboratory confirmation, this incident should also prompt review/reinforcement of the ward’s specimen-transport protocol to ensure CSF samples are transported to the laboratory immediately after collection in future, given how time-critical and irreplaceable this sample type is.
