Abstract
BackgroundData 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).MethodsAll 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.ResultsA 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, 95th confidence interval (CI) 1.00–1.00] and nearly all cases of neuroblastoma (kappa = 0.97, 95th CI 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, 95th CI 0.75–0.80; Burkitt lymphoma – 0.02, 95th CI 0.02–0.07).ConclusionsMisclassification 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2931-8) contains supplementary material, which is available to authorized users.
Highlights
Data from population-based cancer registries are increasingly used to conduct research and guide policy
A total of 380 (9.3 %) were linked probabilistically, with 357 (93.9 %) linked based on Mapping POGONIS diagnostic codes to International classification of childhood cancer (ICCC-3) resulted in the successful assignment of ICCC-3 Level 1 diagnostic groups to all patients and of Level 2 diagnostic subgroups to all but 25 (0.6 %) patients
This was in most cases due to the inappropriate assignment of patients with specific diagnoses to “other” or “miscellaneous” categories, as reflected by the higher number of patients in such categories based on Ontario Cancer Registry (OCR) data as compared to POGONIS data, as opposed to misclassification among different specific types of childhood cancer
Summary
Data from population-based cancer registries are increasingly used to conduct research and guide policy. Cancer registry data have been used to derive population-based estimates of outcome and to track changes in incidence in both adults and children [2,3,4]. When linked to other health administrative data, Cancer registries are often considered gold standards against which other data sources are validated [5, 6]. Despite their impact upon both care and policy, very few studies have examined the validity of cancer registries themselves. While several studies have reported favorably when estimating the completeness of capture of
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