1021. Diagnostic Characteristics of Cerebrospinal Fluid Gram Stain in Children with Suspected Bacterial Meningitis
Session: Poster Abstract Session: Diagnosing Pneumonia and Meningitis
Saturday, October 22, 2011
Room: Poster Hall B1
  • 1021_KateBrizzi.pdf (547.0 kB)
  • Background:  Data on the diagnostic characteristics of cerebrospinal fluid (CSF) Gram stain in bacterial meningitis are limited.  We sought to determine the diagnostic accuracy of CSF Gram stain in the post-pneumococcal vaccine era and the effect of pretreatment with antibiotics on Gram stain characteristics.

    Methods:  We conducted a cross-sectional study of CSF specimens collected from the Children's Hospital of Philadelphia emergency department between January 1, 2002 and August 31, 2010.  Subjects with ventriculoperitoneal shunts or recent neurosurgery were excluded. Subjects were classified as having definite (growth of a known pathogen on CSF culture), probable (growth of an organism on CSF culture and the CSF white blood cell count >500 per mm3 and the CSF glucose < 20mg/dl or elevated CSF protein), or no bacterial meningitis.  Medical records were reviewed for all specimens classified as definite or probable bacterial meningitis.

    Results:  Of the 1,901 specimens, 17 were classified as definite and 4 as probable bacterial meningitis.  Thirty-four specimens had an organism on Gram stain.  The sensitivity of Gram stain was high for those with definite meningitis (94.1%) and those with definite or probable meningitis (95.2%) (Table).  The positive predictive value of CSF Gram stain was only 47.1% for definite meningitis.  Pretreatment with antibiotics did not significantly affect Gram stain sensitivity or specificity. 

    Conclusion:  In the post-pneumococcal vaccine era, the CSF Gram stain remains a sensitive marker for bacterial meningitis, even when antibiotics are given prior to lumbar puncture.  The potential for false positive results highlights the need for diagnostic tests with greater specificity to minimize the likelihood of overtreatment of uninfected patients.

    Table. Diagnostic accuracy of CSF Gram stain for bacterial meningitis.

    Definite Meningitis


    Definite or Probable Meningitis (n=21)

    Sensitivity (%)

    94.1 (71.3 – 99.9)

    95.2 (76.2 – 99.9)

    Specificity (%)

    89.8 (84.3 – 93.8)

    91.9 (86.7 – 95.5)

    Positive Predictive Value (%)

    47.1 (29.8 – 64.9)

    58.8 (40.7 – 75.4)

    Negative Predictive Value (%)

    99.4 (96.5 – 100.0)

    99.4 (96.5 – 100.0)

    Subject Category: D. Diagnostic microbiology

    Kate Brizzi1, Elizabeth Hines, BA2, Xianqun Luan2 and Samir Shah, MD, MSCE2, (1)University of Pennsylvania School of Medicine, Philadelphia, PA, (2) Center for Pediatric Clinical Effectiveness, Children's Hospital of Philadelphia, Philadelphia, PA


    K. Brizzi, None

    E. Hines, None

    X. Luan, None

    S. Shah, None

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