Increase in the CSF leukocyte count in a patient with external ventricular CSF catheter is strongly suggestive of catheter-associated infection, according to a study carried out at a teaching hospital in The Hague, Netherlands and reported in the journal Neurology Clinical Practice.¹

This single-center observational study included 103 patients in intensive care with an external ventricular CSF catheter for conditions like intracranial hemorrhage and CNS malignancies. Patients with CNS infection and those who were not expected to survive beyond a day were not included in the trial. Their median age was 61 years and almost half of the study population was female.

Data for Glasgow Coma Scale (GCS) and body temperature was gathered from the day of hospitalization to the day of discharge from the hospital. The definition proposed by the 2017 IDSA guidelines for Healthcare-Associated Ventriculitis and Meningitis was used to categorize patients with infection of the CSF drain catheter, which is “single or multiple positive CSF cultures with CSF pleocytosis and/or hypoglycorrhachia, or an increasing cell count, and clinical symptoms suspicious for ventriculitis or meningitis”.² Day 0 was taken as the day when the positive culture sample was collected. In this study, the researchers aimed to examine the usefulness of clinical features including biochemical and microbiological parameters in the diagnosis of external ventricular CSF catheter-associated infection.

Analysis showed that catheter-associated infection developed in 15 of the 103 patients in a median time of 9 days (3-16 days). Patients with catheter infection also had longer median drainage time (13 vs 9 days). Eighty-five percent (11/13) of patients with infection were febrile (>38.0°C) compared to 56% (21/39) without the infection. While the sensitivity was 85%, the specificity was just 46%.

Ninety-two (8%) of 1158 CSF cultures were positive; of these 52 cultures were infections, while the remaining 40 were secondary to contamination and therefore considered to be “no infection” cases. CSF cultures were positive following CSF collection after a median of 3 days (ranging up to 8 days) after collecting the sample. A positive Gram stain could diagnose 8 out of the 15 patients (53%) with the infection.

On Day 0, it was difficult to distinguish between patients with infection or those without infection by any clinical parameter (GCS) or tests. However, the leukocytes in CSF were raised in patients with ventricular catheter-associated infection vs those who did not have an infection on Days +2 and +3. The CSF leukocyte count cut-off level was taken as >1,000 × 10⁶/L. The between-group difference was most evident on day +2 (1,703 × 10⁶/L vs 80 × 10⁶/L). The percentage of polymorphonuclear cells (PMNs) was increased in patients with infection on days +1 and +2 (day +2 89% vs 59%). The sensitivity for the cut-off level of CSF leukocytes was 67% and the specificity was 100%. The positive predictive value (PPV) was 100%, while the negative predictive value was 92%. Daily CSF examination offered no added advantages.

Diagnosis of ventricular catheter-associated infection is not easy. The gold standard test for the diagnosis of ventricular catheter-associated infection is CSF culture. However, culture results may take days, which may not even be positive. False negative results are often obtained. So, antibiotics are started empirically.

This study has shown that in patients with an external ventricular CSF catheter, a raised CSF leukocyte count and an increased percentage of PMNs are strongly indicative of catheter-associated infection much before culture results are available. Positive Gram staining was diagnostic for the catheter-associated infection with a PPV of 100%, note the authors. CSF Gram staining is therefore recommended to be done as a routine in patients with suspected catheter-associated infection.

References

1. Dorresteijn KI, et al. Diagnostic accuracy of clinical signs and biochemical parameters for external ventricular CSF catheter-associated infection. Neurol Clin Pract. 2022 Aug;12(4):298-306. doi: 10.1212/CPJ.0000000000200059.
2. Tunkel AR, et al.2017 Infectious Diseases Society of Americas clinical practice guidelines for healthcare-associated ventriculitis and meningitis. Clin Infect Dis. 2017 Mar 15;64(6):e34-e65. doi: 10.1093/cid/ciw861.