From the Guidelines
To correct for white blood cells and red blood cells in cerebral spinal fluid, subtract 1 white cell for every 700 red blood cells, as this is the most commonly accepted approximation in clinical practice, as noted in 1 and 1. When interpreting cerebrospinal fluid (CSF) results, it is essential to consider the potential for contamination with blood, which can lead to inaccurate cell counts.
- The correction factor for red blood cells (RBCs) and white blood cells (WBCs) in CSF is crucial for accurate diagnosis and treatment of conditions such as meningitis and subarachnoid hemorrhage.
- According to 1 and 1, a common approximation for correcting WBC counts is to subtract 1 WBC for every 700 RBCs, which is a widely accepted method in clinical practice.
- However, it is also important to note that this correction factor may not be applicable in all cases, particularly in patients with hemorrhagic CSF, as seen in HSV encephalitis, where the presence of RBCs may be a result of the underlying pathology rather than contamination, as mentioned in 1 and 1.
- In such cases, the clinical context and other CSF parameters, such as glucose and protein levels, should be taken into consideration when interpreting the results, as highlighted in 1.
- Additionally, the use of more complicated formulae, which take into account factors such as anemia, may be necessary in certain situations, as noted in 1.
- The most recent and highest quality study, 1, provides a comprehensive overview of the classical CSF features of different causes of meningitis, including bacterial, viral, tuberculous, and fungal meningitis, which can aid in the accurate diagnosis and treatment of these conditions.
From the Research
Correction Factors for RBCs and White Blood Cells in Cerebral Spinal Fluid
- The correction factor for cerebrospinal fluid WBC counts in infants with traumatic lumbar punctures was derived as a cerebrospinal fluid RBCs:WBCs ratio of 877:1 (95% confidence interval [CI] 805 to 961:1) 2.
- A study on neonates with traumatic lumbar puncture found that the best results for effective WBC correction were the method based on the peripheral blood ratio and the 400:1 ratio, with sensitivity and specificity of 1.0 and 0.9 for bacterial meningitis, and sensitivity and specificity of 0.8 and 0.9 for viral meningitis 3.
- For adults with traumatic lumbar puncture, specificities and sensitivities of commonly used CSF correction factors (1 WBC:500 RBC, 1 WBC:1000 RBC, and 1 WBC:1500 RBC) were calculated, with 1 WBC:500 RBC having the highest specificity for pleocytosis, and 1 WBC:1500 RBC having the highest sensitivity 4.
- The presence of nucleated RBCs in circulating blood can falsely elevate the leukocyte count, and manual correction of the leukocyte count is warranted, with cutoff values for correcting white blood cell count for nucleated RBCs including 1,5,10,20, and 50 5.
Application of Correction Factors
- Correction of the cerebrospinal fluid WBC count can substantially reduce the number of infants with cerebrospinal fluid pleocytosis, but may misclassify some infants with bacterial meningitis 2.
- The use of correction factors can help clarify the diagnosis of neonatal meningitis, offering neonatologists the possibility to assess the WBC count in traumatic LP 3.
- In adults with traumatic lumbar puncture, indicators of false pleocytosis include bloodier CSF and milder pleocytosis, suggesting that correction factors are most useful in such cases 4.