From the Guidelines
A normal CSF cell count can contain up to 5 WBCs per microliter (μL), as indicated by the most recent and highest quality study 1. This is based on the guideline evidence from the UK Joint Specialist Societies guideline on the diagnosis and management of acute meningitis and meningococcal sepsis in immunocompetent adults, which provides a comprehensive overview of CSF features in different causes of meningitis. The key points to consider are:
- Normal CSF typically contains less than 5 WBCs/μL, with the predominant cell type being lymphocytes or monocytes.
- The presence of these cells in limited numbers represents normal immune surveillance of the cerebrospinal fluid.
- An elevation above the reference range of 5 WBCs/μL may indicate infection, inflammation, or other pathological processes affecting the central nervous system. Some important considerations in CSF analysis include:
- The total WBC count is crucial for diagnostic purposes.
- The differential count (types of WBCs present) is also important, as a predominance of neutrophils often suggests bacterial infection, while lymphocyte predominance may indicate viral infection or certain inflammatory conditions. It's worth noting that other studies, such as the case definitions, diagnostic algorithms, and priorities in encephalitis consensus statement 1, may provide additional context, but the most recent and highest quality study 1 takes precedence in guiding clinical decision-making.
From the Research
Normal CSF Cell Count
A normal CSF cell count is typically characterized by the absence or low levels of white blood cells (WBCs) [ 2, 3, 4, 5 ].
Presence of WBCs in Normal CSF
- A study published in 2020 found that the presence of WBCs in CSF after a lumbar puncture is rare and should lead to careful exclusion of other diseases, especially inflammatory ones [ 5 ].
- Another study from 2022 evaluated the use of the BioFire FilmArray Meningitis/Encephalitis Panel and found that in non-immunocompromised patients with ≤ 10 CSF WBCs, none of the positive results were judged clinically significant [ 4 ].
- The American Family Physician journal states that CSF analysis can help in the evaluation of various neurologic conditions, including meningitis, which is characterized by high levels of WBCs in the CSF [ 2 ].
- The Handbook of Clinical Neurology also mentions that CSF cell count is a useful laboratory test for identifying the organism and differentiating between bacterial and viral meningitis [ 3 ].