title: Predictive value of seizure ICD-9 codes for vaccine safety research.
abstract: Post-licensure vaccine safety studies often monitor for seizures using automated screening of ICD-9 codes. This study assessed the positive predictive value (PPV) of ICD-9 codes used to identify seizure visits in children aged 6 weeks to 23 months who were enrolled in seven managed care organizations during January 2000 to December 2005. ICD-9 codes were used to identify visits for seizures in the 0-30-day period following receipt of a pneumococcal vaccine. Visits were stratified by setting of diagnosis (emergency department (ED), outpatient, and inpatient). Review of medical records confirmed whether the visit represented a true acute seizure event. 3233 visits for seizures were identified; 1024 were randomly selected for medical record review and 859 (84%) had records available. The PPV of ICD-9 codes was highest in the ED setting (97%), followed by the inpatient setting (64%). In the outpatient setting, computerized codes for seizures had very low PPV: 16% on days 1-30 following vaccination and 2% for visits on the same day of vaccination. An estimated 77% of true seizures identified were from the ED or inpatient settings. In conclusion, when using ICD-9 codes to identify seizure outcomes, restricting to the ED and inpatient settings of diagnosis may result in less biased preliminary analyses and more efficient vaccine safety studies.
authors.affiliation: Department of Ambulatory Care and Prevention, Harvard Pilgrim Health Care and Harvard Medical School, Boston, MA 02215, United States. irene_shui@hphc.org
authors.forename: Irene M
authors.initials: IM
authors.lastname: Shui
authors.forename: Ping
authors.initials: P
authors.lastname: Shi
authors.forename: M Maya
authors.initials: MM
authors.lastname: Dutta-Linn
authors.forename: Eric S
authors.initials: ES
authors.lastname: Weintraub
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Hambidge
authors.forename: James D
authors.initials: JD
authors.lastname: Nordin
authors.forename: Tracy A
authors.initials: TA
authors.lastname: Lieu
mesh_terms: D000554:Ambulatory Care Facilities / Q000706:statistics & numerical data; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007223:Infant; D038801:International Classification of Diseases; D008297:Male; D022242:Pneumococcal Vaccines / Q000009:adverse effects*; D011237:Predictive Value of Tests; D012640:Seizures / Q000139:chemically induced / Q000175:diagnosis*; D014611:Vaccination / Q000009:adverse effects*
chemical_list: D022242:Pneumococcal Vaccines