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Are polymorphonuclear leukocytes an abnormal finding in cerebrospinal fluid? Results from 225 normal cerebrospinal
1Department of Medicine, UCLA.
Abstract:
Although it is often claimed that the presence of a single polymorphonuclear leukocyte (PMN) in the cerebrospinal fluid (CSF) is abnormal, recently some have suggested that a few PMNs are occasionally present in cytocentrifuged differential cell counts of normal CSF. We examined 225 consecutive normal CSF specimens to determine how frequently PMNs occur in normal CSF and to identify factors associated with the presence of PMNs. One or more PMNs were present in 73 cases (32%). The number of CSF PMNs was strongly correlated with the degree of CSF blood contamination and the hematologic PMN count. Of the 163 specimens having 25 red blood cells or less per cubic millimeter, only eight (5%) had three or more PMNs, and these outliers had abnormally high hematologic PMN counts. Of the 36 specimens having 100 red blood cells or more per cubic millimeter, 17 (47%) had six or more PMNs. We conclude that the number of PMNs found on cytocentrifuged differential cell counts is highly dependent on the degree of CSF blood contamination and the patient's hematologic PMN count and that even minimal blood contamination can result in the presence of one to two PMNs in normal CSF.
Insights
The presence of polymorphonuclear leukocytes (PMNs) in cerebrospinal fluid (CSF) can occur in normal individuals, especially with minor blood contamination. CSF PMN counts are linked to blood contamination levels and the patient's blood PMN levels.
Area of Science:
- Neurology
- Hematology
- Clinical Pathology
Background:
- The interpretation of polymorphonuclear leukocytes (PMNs) in cerebrospinal fluid (CSF) is critical for diagnosing neurological infections.
- Traditionally, even a single PMN in CSF was considered indicative of pathology, but recent findings suggest occasional presence in normal samples.
Purpose of the Study:
- To investigate the frequency of PMNs in normal CSF specimens.
- To identify factors influencing PMN presence in normal CSF.
Main Methods:
- Analysis of 225 consecutive normal CSF specimens.
- Evaluation of cytocentrifuged differential cell counts.
- Correlation of CSF PMN counts with CSF blood contamination and hematologic PMN counts.
Main Results:
- One or more PMNs were detected in 32% of normal CSF specimens.
- CSF PMN counts significantly correlated with blood contamination and peripheral blood PMN levels.
- Specimens with minimal blood contamination showed minimal PMN presence, while higher contamination correlated with more PMNs.
Conclusions:
- The presence and number of PMNs in normal CSF are strongly influenced by blood contamination.
- Even slight blood contamination can lead to the detection of 1-2 PMNs in CSF.
- Peripheral blood PMN counts are a key factor in interpreting CSF PMN findings.