Brief Report
Cerebrospinal fluid/blood glucose ratio as an indicator for bacterial meningitis

https://doi.org/10.1016/j.ajem.2013.11.030Get rights and content

Abstract

Background

Bacterial meningitis is an emergent disease requiring prompt diagnosis and treatment with appropriate antimicrobials. Although the lumbar puncture is widely used as a diagnostic tool for bacterial meningitis, it remains unclear which value in cerebrospinal fluid (CSF) analysis in emergency laboratory tests precisely predicts the presence of bacterial meningitis.

Methods

This is a single-center, retrospective review of medical records to determine which emergency laboratory CSF test results are useful for predicting bacterial meningitis. The diagnosis of meningitis is made when the white blood cell count in CSF exceeds 5 cells/μL, while the diagnosis of bacterial meningitis additionally requires the growth of a pathogen from a CSF culture or the identification of a pathogen in Gram staining of CSF specimen.

Results

We identified 15 patients with bacterial meningitis and 129 patients with aseptic meningitis. While neutrophil-predominant pleocytosis and a decreased glucose level in CSF can predict the presence of bacterial meningitis, the CSF/blood glucose ratio is more precise (optimal cut-off = 0.36, sensitivity = 92.9%, specificity = 92.9%, area under the curve = .97) even after administration of antimicrobials prior to examination in the emergency department.

Conclusion

This study suggests that the CSF/blood glucose ratio may be a better single indicator for bacterial meningitis. Since the CSF glucose and blood glucose values are promptly and easily obtained from a lumbar puncture, the CSF/blood glucose ratio should be considered as a timely diagnostic indicator of bacterial meningitis. It may also help exclude the diagnosis of bacterial meningitis especially in cases in which no microorganisms can be cultured.

Introduction

Bacterial meningitis is an emergent, life-threatening, infectious disease which requires prompt diagnosis and appropriate antimicrobial therapy. Keeping meningitis in mind as a differential diagnosis, the physician should perform a lumbar puncture if none of the clinical findings can adequately rule out this disease [1]. The presence of pleocytosis confirms the diagnosis of meningitis, but it may not always predict the presence of bacterial meningitis, which requires treatment with antimicrobials. The use of empiric antimicrobials is justified if the physician suspects bacterial meningitis; however, whenever possible, the physician should refrain from administering antimicrobials without adequate medical grounds for their use.

The association between emergency laboratory examinations of cerebrospinal fluid (CSF) and the diagnosis of bacterial meningitis has rarely been reassessed since the 1980s [2], [3], [4]. A recent study reported that CSF lactate concentration is a better, single indicator for predicting bacterial meningitis than conventional markers such as CSF glucose, CSF/blood glucose ratio, CSF protein and CSF total number of leukocytes [5], [6]. However, the CSF lactate level is likely to be affected by the administration of antimicrobials [6], and measuring CSF lactate is not routinely performed. Several management guidelines for bacterial meningitis have noted that the measurement of conventional markers in CSF should be considered when assessing the possibility of bacterial meningitis. Given the lack of recent studies examining the utility of emergency laboratory examinations of CSF for predicting the presence of bacterial meningitis, we investigated the diagnostic value of this method for predicting bacterial meningitis at a Japanese tertiary care center.

Section snippets

Study setting

This study was conducted at the Tokyo Metropolitan Tama Medical Center, a 789-bed tertiary care teaching hospital in Tokyo, Japan. The emergency department (ED) at this institution takes in an average of approximately 38,000 patients, including 7,200 ambulances, annually. The study was approved by the institutional review board of Tokyo Metropolitan Tama Medical Center with a waiver of informed consent to review the patient records.

Study design and participants

The current retrospective study consists of a review of medical

Results

A total of 573 patients who underwent a lumbar puncture between January 1, 2006, and November 31, 2012, were identified. Fifty-two of these patients were excluded because they met the exclusion criteria (hydrocephalus: 11, subarachnoid hemorrhage: 7, traumatic tap: 5, Guillain-Barré syndrome: 5, multiple sclerosis: 3, neurosarcoidosis: 2, central nervous system metastasis: 2, HIV encephalopathy: 1, and incomplete medical record: 6). We subsequently excluded 10 additional cases of meningitis

Discussion

Although the use of empiric antimicrobials is justified if the physician suspects bacterial meningitis after a comprehensive examination of the patient’s medical history and symptoms, the present study suggests that the CSF/blood glucose ratio has demonstrable utility for the diagnosis of bacterial meningitis, and may thus expedite the physician’s decision as to whether or not to administer antimicrobials.

The several studies assessing CSF analysis in patients with meningitis were mostly

Conclusion

This study demonstrates that the CSF/blood glucose ratio may predict the presence of bacterial meningitis more precisely than other routinely measured markers in CSF. Since the CSF glucose levels and blood glucose levels are promptly available, the CSF/blood glucose ratio should be examined as a timely diagnostic indicator for bacterial meningitis. To assess the presence of bacterial meningitis comprehensively, the CSF/blood glucose ratio in combination with other signs, symptoms, and

Declaration

We investigated the same cohort in another article [1]. However the subjects of the articles are independent of one another.

Acknowledgments

We thank Dr Hiroyoshi Y. Tanaka for his reading of the manuscript and his suggestions for improving its contents, Dr Keita Tatsuno for his various invaluable suggestions, Mr Keigo Morita for his unflagging diligence in gathering the references, and all of the staff and patients who contributed to this study.

References (12)

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