From the Guidelines
Cerebrospinal fluid (CSF) should be processed within 2 hours of lumbar puncture (LP) for optimal laboratory test results, as certain components begin to degrade after this time, affecting interpretation. The stability of CSF components varies, with cell counts being the most time-sensitive, as white blood cells start lysing after 2 hours, leading to falsely low counts 1. Glucose levels remain relatively stable for 2-3 hours but then begin to decrease due to cellular metabolism. Protein measurements are more stable and can remain valid for up to 24 hours. Microbiological cultures should be set up as soon as possible, ideally within 1 hour, as organism viability decreases over time, potentially leading to false-negative results.
Key Considerations for CSF Processing
- Cell counts: should be performed within 2 hours to avoid falsely low counts due to white blood cell lysis
- Glucose levels: relatively stable for 2-3 hours, then decrease due to cellular metabolism
- Protein measurements: stable for up to 24 hours
- Microbiological cultures: should be set up within 1 hour for optimal results
The provided guidelines primarily focus on the management of acute meningitis and meningococcal sepsis, as well as viral encephalitis, rather than the specifics of CSF handling after LP 1. However, the general principle of timely processing for accurate laboratory results applies. If immediate processing isn't possible, refrigeration at 4°C can extend stability for some tests, but this isn't ideal for all components. The degradation of CSF components occurs because cells continue metabolic processes, proteins may break down, and any microorganisms present can either die off or multiply depending on conditions, all of which alter the sample's composition from its original state.
From the Research
Cerebrospinal Fluid (CSF) Analysis After Lumbar Puncture (LP)
- The provided studies do not directly address the question of how long CSF can be left at bedside after a lumbar puncture before it can no longer be interpreted for laboratory tests.
- However, some studies provide information on the handling and analysis of CSF samples, which may be relevant to the question.
- According to 2 and 3, CSF specimens should be centrifuged at >2000 rpm for 5 min as soon as possible after receipt in the laboratory, and the supernatant should be stored at 4 degrees C in the dark until analysis.
- It is also recommended to protect the CSF from light and avoid vacuum tube transport systems, if possible 2, 3.
- The studies do not provide a specific time limit for how long CSF can be left at bedside before analysis, but they emphasize the importance of handling and storing the samples properly to ensure accurate results.
- In general, it is recommended to analyze CSF samples as soon as possible after collection to minimize the risk of contamination, degradation, or other factors that may affect the results.
- Further research is needed to determine the specific time frame for CSF analysis after lumbar puncture.