Lunardi et al reviewed the diagnosis of external ventricular drain-related infections of the central nervous system. These can be difficult to diagnose. The authors are from Federal University of Rio Grande do Sul, Hospital de Clinicas de Porto Alegre and the Brain Institute of Rio Grande do Sul in Brazil.
Tests for the diagnosis of infections associated with an external ventricular drain:
(1) Cell Index (CI) of Pfausler et al
(2) elevated CSF lactate (>= 4 mmol/L)
(3) positive CSF culture
(4) positive CSF PCR
An elevated CSF lactate and a positive culture are helpful when positive but can be insensitive.
CSF cell index =
= (CSF leukocyte count in 10^6/L) * (erythrocyte count in blood in 10^12/L) / ((leukocyte count in blood in 10^9/L) * (CSF erythrocyte count in 10^6/L))
For patients with a history of subarachnoid hemorrhage a CI >= 2.8 had a sensitivity and specificity of 100%.
For patients with other diagnoses a CI >= 2.9 had a sensitivity of 95% and specificity of 93%.
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