Summarizing an old article on the CSF Cell Index published in 2004, study has not been validated, but information is “nice to know.”
The CSF cell index is a ratio between the blood cells in the ventricles (in intracranial hemorrhage) and the peripheral blood. At the time of bleeding, blood in the ventricles is diluted within the CSF, and the relationship between WBC:RBC should equal that in the peripheral blood. This ratio, called the CSF cell index, should approximate 1 in the absence of infection.
The CSF cell index is calculated using to the following formula:
This study reported that the cell index rises 3 days before diagnosis of a catheter-related ventriculitis, and proper antimicrobial treatment led to a rapid decrease of the cell index. The study concluded that a significant increase in the cell index is highly indicative of nosocomial EVD-related ventriculitis in patients with IVH, and that the increase of the cell index usually precedes diagnosis by conventional means by 3 days.
Pfausler, B. et al. “Cell Index ? A New Parameter For The Early Diagnosis Of Ventriculostomy (External Ventricular Drainage)-Related Ventriculitis In Patients With Intraventricular Hemorrhage?”. Acta Neurochirurgica 146.5 (2004): 477-481.