title: The validity of pediatric cancer diagnoses in a population-based general cancer registry in Ontario, Canada.
abstract: Data from population-based cancer registries are increasingly used to conduct research and guide policy. However, few validation studies of cancer registry data have been conducted, particularly among children. We therefore aimed to determine the validity of pediatric diagnostic data in the Ontario Cancer Registry (OCR).
  
  
  
  All children diagnosed with any malignancy between 2000-2011 in Ontario, Canada were identified through the Pediatric Oncology Group of Ontario Networked Information System (POGONIS), a pediatric cancer registry actively maintained by trained data managers, and linked to the OCR. International Classification of Diseases for Oncology codes for each patient were taken from the OCR and converted to International Classification of Childhood Cancer (ICCC-3) diagnostic groups and subgroups using published algorithms. OCR-based ICCC-3 groupings were then validated by comparing them to gold standard diagnostic information from POGONIS.
  
  
  
  A total of 4448 patients met inclusion criteria; 4073 (91.6 %) were successfully linked to the OCR. Diagnostic accuracy was excellent for many childhood solid tumors. For example, the OCR correctly identified all cases of retinoblastoma [kappa = 1.00, 95thconfidence interval (CI) 1.00-1.00] and nearly all cases of neuroblastoma (kappa = 0.97, 95thCI 0.96-0.99). Hematologic and central nervous system (CNS) cancers, the most common childhood malignancies, were however often misclassified with inferior kappas (acute lymphoblastic leukemia - 0.77, 95thCI 0.75-0.80; Burkitt lymphoma - 0.02, 95thCI 0.02-0.07).
  
  
  
  Misclassification of common pediatric hematologic and CNS cancers was significant and may lead to inaccurate incidence and survival estimates using cancer registry data. Validation studies of pediatric data in other registries are necessary to identify practices and procedures leading to the highest quality information.
authors.affiliation: Division of Haematology/Oncology and Program in Child Health Evaluative Sciences, The Hospital for Sick Children, 555 University Avenue, Toronto, M5G 1X8, Canada. sumit.gupta@sickkids.ca.|Department of Paediatrics, Faculty of Medicine, and Institute for Health Policy, Management, and Evaluation, University of Toronto, 155 College Street, Suite 425, Toronto, M5T 3M6, Canada. sumit.gupta@sickkids.ca.|Cancer Research Program, Institute for Clinical Evaluative Sciences, 2075 Bayview Avenue, G1 06, Toronto, M4N 3M5, Canada. sumit.gupta@sickkids.ca.
authors.forename: Sumit
authors.identifier: 0000-0003-1334-3670
authors.initials: S
authors.lastname: Gupta
authors.affiliation: Cancer Research Program, Institute for Clinical Evaluative Sciences, 2075 Bayview Avenue, G1 06, Toronto, M4N 3M5, Canada.|Pediatric Oncology Group of Ontario, 480 University Avenue, Suite 1014, Toronto, M5G 1V2, Canada.
authors.forename: Jason D
authors.initials: JD
authors.lastname: Pole
mesh_terms: D000367:Age Factors; D006801:Humans; D009369:Neoplasms / Q000175:diagnosis* / Q000453:epidemiology*; D009864:Ontario / Q000453:epidemiology; D010372:Pediatrics / Q000706:statistics & numerical data*; D011159:Population Surveillance; D012042:Registries; D015203:Reproducibility of Results
keywords: Cancer; Child; Health services research; Registry; Validation