title: Validation of a clinical prediction rule to distinguish Lyme meningitis from aseptic meningitis.
abstract: OBJECTIVE
  The "Rule of 7's," a Lyme meningitis clinical prediction rule, classifies children at low risk for Lyme meningitis when each of the following 3 criteria are met: <7 days of headache, <70% cerebrospinal fluid (CSF) mononuclear cells, and absence of seventh or other cranial nerve palsy. The goal of this study was to test the performance of the Rule of 7's in a multicenter cohort of children with CSF pleocytosis.
  
  
  METHODS
  We performed a retrospective cohort study of children evaluated at 1 of 3 emergency departments located in Lyme disease-endemic areas with CSF pleocytosis and Lyme serology obtained. Lyme meningitis was defined using the Centers for Disease Control and Prevention criteria (either positive Lyme serology test result or an erythema migrans [EM] rash). We calculated the performance of the Rule of 7's in our overall study population and in children without physician-documented EM.
  
  
  RESULTS
  We identified 423 children, of whom 117 (28% [95% confidence interval (CI): 24%-32%]) had Lyme meningitis, 306 (72% [95% CI: 68%-76%]) had aseptic meningitis, and 0 (95% CI: 0%-1%) had bacterial meningitis. Of the 130 classified as low risk, 5 had Lyme meningitis (sensitivity, 112 of 117 [96% (95% CI: 90%-99%)]; specificity, 125 of 302 [41% (95% CI: 36%-47%)]). In the 390 children without EM, 3 of the 127 low-risk patients had Lyme meningitis (2% [95% CI: 0%-7%]).
  
  
  CONCLUSIONS
  Patients classified as low risk by using the Rule of 7's were unlikely to have Lyme meningitis and could be managed as outpatients while awaiting results of Lyme serology tests.
authors.affiliation: Division of Emergency Medicine, Children's Hospital and Harvard Medical School, Boston 300 Longwood Ave, Boston, MA 02115, USA.
authors.forename: Keri A
authors.initials: KA
authors.lastname: Cohn
authors.forename: Amy D
authors.initials: AD
authors.lastname: Thompson
authors.forename: Samir S
authors.initials: SS
authors.lastname: Shah
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Hines
authors.forename: Todd W
authors.initials: TW
authors.lastname: Lyons
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Welsh
authors.forename: Lise E
authors.initials: LE
authors.lastname: Nigrovic
mesh_terms: D000293:Adolescent; D025065:Borrelia burgdorferi / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D003389:Cranial Nerve Diseases / Q000209:etiology; D003661:Decision Support Techniques; D003937:Diagnosis, Differential; D005260:Female; D006261:Headache / Q000209:etiology; D006801:Humans; D007223:Infant; D007964:Leukocytosis / Q000134:cerebrospinal fluid; D020852:Lyme Neuroborreliosis / Q000134:cerebrospinal fluid / Q000150:complications / Q000175:diagnosis*; D008297:Male; D008582:Meningitis, Aseptic / Q000134:cerebrospinal fluid / Q000150:complications / Q000175:diagnosis*; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013129:Spinal Puncture; D055815:Young Adult