Effect of Hemorrhagic Lumbar Puncture on CSF Protein and Analysis Interpretation
Yes, a hemorrhagic lumbar puncture will increase CSF protein levels and can significantly affect the interpretation of CSF analysis. For every 1000 red blood cells/mm³ in the CSF, protein increases by approximately 1.1 mg/dL 1.
Impact on CSF Parameters
- Blood contamination from a traumatic lumbar puncture leads to falsely elevated CSF protein concentrations, with even low levels of contamination (2,500 erythrocytes/μL) causing false pathological results of total protein and albumin 2
- As the amount of blood contamination increases, the frequency of false pathological protein results also increases 2
- A blood contamination of 5,000 erythrocytes/μL can result in a false positive intrathecal IgM production in nearly 20% of cases 2
- CSF glucose levels typically remain unchanged with blood contamination from traumatic taps 3
Correction Methods for Traumatic Taps
- The standard approximation for white blood cell correction is to subtract 1 white cell for every 700 red blood cells in the CSF 4
- More complicated formulas that account for factors like anemia are available but the simple approximation is sufficient in most circumstances 4
- For protein levels, the correction factor of approximately 1.1 mg/dL increase per 1000 RBCs/mm³ can be applied 1
Distinguishing Traumatic Tap from True Pathology
- The "three tube test" can help distinguish a traumatic tap from true subarachnoid hemorrhage - in a traumatic tap, the RBC count typically decreases from the first to the third tube 5
- In true subarachnoid hemorrhage, the CSF red cell count remains relatively constant across all tubes 5
- Xanthochromia (yellow discoloration of CSF) is critical in distinguishing traumatic taps from true subarachnoid hemorrhage - it appears within 12 hours of a true hemorrhage but is absent in fresh traumatic taps 5
- Erythrophages and siderophages (macrophages that have ingested red blood cells or hemosiderin) do not develop in vitro from traumatic taps, so their presence indicates true subarachnoid hemorrhage 2
Clinical Implications
- In suspected viral encephalitis, a blood-stained CSF may reflect the hemorrhagic pathophysiology of conditions like HSV encephalitis, especially if serial CSF specimens are consistently blood-stained 4
- HSV encephalitis can be hemorrhagic, with elevated CSF red cell counts in approximately 50% of cases 4
- When interpreting CSF results in the context of potential meningitis, the degree of blood contamination must be considered, as it can mask or mimic pathological findings 4, 2
Practical Approach to Interpretation
- Always note the RBC count in CSF when interpreting protein levels 2, 1
- Apply appropriate correction formulas based on the degree of blood contamination 4, 1
- Consider the clinical context - in some conditions like HSV encephalitis, blood in the CSF may be part of the disease process rather than contamination 4
- Extensive CSF testing may not be necessary for all patients with traumatic taps - limitation of sophisticated testing to samples with abnormal cell counts or chemistries after correction can result in cost savings without compromising care 6
Common Pitfalls to Avoid
- Failing to correct for blood contamination when interpreting CSF protein and cell counts 2, 1
- Misinterpreting a traumatic tap as pathological, leading to unnecessary treatment or interventions 5
- Overlooking true pathology by attributing all abnormalities to blood contamination 4
- Performing unnecessary extensive CSF testing when initial corrected values are normal 6