title: Establishment of an 11-year cohort of 8733 pediatric patients hospitalized at United States free-standing children's hospitals with de novo acute lymphoblastic leukemia from health care administrative data.
abstract: BACKGROUND
  Acute lymphoblastic leukemia (ALL) accounts for almost one quarter of pediatric cancer in the United States. Despite cooperative group therapeutic trials, there remains a paucity of large cohort data on which to conduct epidemiology and comparative effectiveness research studies.
  
  
  METHODS
  We designed a 3-step process utilizing International Classification of Diseases-9 Clinical Modification (ICD-9) discharge diagnoses codes and chemotherapy exposure data contained in the Pediatric Health Information System administrative database to establish a cohort of children with de novo ALL. This process was validated by chart review at 1 of the pediatric centers.
  
  
  RESULTS
  An ALL cohort of 8733 patients was identified with a sensitivity of 88% [95% confidence interval (CI), 83%-92%] and a positive predictive value of 93% (95% CI, 89%-96%). The 30-day all cause inpatient case fatality rate using this 3-step process was 0.80% (95% CI, 0.63%-1.01%), which was significantly different than the case fatality rate of 1.40% (95% CI, 1.23%-1.60%) when ICD-9 codes alone were used.
  
  
  CONCLUSIONS
  This is the first report of assembly and validation of a cohort of de novo ALL patients from a database representative of free-standing children's hospitals across the United States. Our data demonstrate that the use of ICD-9 codes alone to establish cohorts will lead to substantial patient misclassification and result in biased outcome estimates. Systematic methods beyond the use of just ICD-9 codes must be used before analysis to establish accurate cohorts of patients with malignancy. A similar approach should be followed when establishing future cohorts from administrative data.
authors.affiliation: *Division of Infectious Diseases †Center for Pediatric Clinical Effectiveness, The Children's Hospital of Philadelphia ‡Department of Pediatrics §Center for Clinical Epidemiology and Biostatistics, the Perelman School of Medicine at the University of Pennsylvania ∥Division of Oncology, The Children's Hospital of Philadelphia ¶Department of Biostatistics and Epidemiology, the Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Fisher
authors.forename: Tracey
authors.initials: T
authors.lastname: Harris
authors.forename: Kari
authors.initials: K
authors.lastname: Torp
authors.forename: Alix E
authors.initials: AE
authors.lastname: Seif
authors.forename: Ami
authors.initials: A
authors.lastname: Shah
authors.forename: Yuan-Shung V
authors.initials: YS
authors.lastname: Huang
authors.forename: L Charles
authors.initials: LC
authors.lastname: Bailey
authors.forename: Leslie S
authors.initials: LS
authors.lastname: Kersun
authors.forename: Anne F
authors.initials: AF
authors.lastname: Reilly
authors.forename: Susan R
authors.initials: SR
authors.lastname: Rheingold
authors.forename: Dana
authors.initials: D
authors.lastname: Walker
authors.forename: Yimei
authors.initials: Y
authors.lastname: Li
authors.forename: Richard
authors.initials: R
authors.lastname: Aplenc
mesh_terms: D000293:Adolescent; D000328:Adult; D000970:Antineoplastic Agents / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D059019:Clinical Coding; D015331:Cohort Studies; D057186:Comparative Effectiveness Research / Q000706:statistics & numerical data; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006776:Hospitals, Pediatric / Q000706:statistics & numerical data*; D006801:Humans; D007223:Infant; D008297:Male; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy* / Q000453:epidemiology / Q000401:mortality; D014481:United States / Q000453:epidemiology; D055815:Young Adult
chemical_list: D000970:Antineoplastic Agents