Applicability to our patient population may be limited by several factors. First, the population in this study may represent a group with more severe illness than most children with meningitis, as stated previously. Second, although a demographic profile of the patient population served by Sophia Children's Hospital is not provided, there are likely to be considerable differences between the populations of Rotterdam, the Netherlands, and Washington, DC, in terms of ethnicity, education level, epidemiological factors related to meningitis, and other issues. In addition, the study occurred during the prevaccination period in which Haemophilus influenzae type B (Hib) was more frequently a cause of meningitis. This factor could affect the use of the rule in any country with universal Hib vaccination. The authors acknowledge this fact and state that modification of the results to exclude patients with Hib yielded the same CSF and clinical-scoring rule. Furthermore, widespread use of conjugate pneumococcal vaccine may limit the applicability of these results to future practice if this vaccine significantly affects epidemiological factors regarding bacterial meningitis, as has been predicted.7 Other causes of meningitis, such as Lyme disease, apparently were not considered but are relatively common in our population. Finally, the study examined patients aged 1 month to 15 years. Many pediatricians support obtaining a lumbar puncture in infants up to age 3 months for the evaluation of fever, bypassing the application of the initial clinical rule in this age group. More information is needed regarding the use of this rule in very young infants.