ACCURACY AND COMPLETENESS OF THE REGISTRATION OF CHILDHOOD LEUKEMIA IN THE NETHERLANDS, 1989-1992

In The Netherlands, childhood leukaemia is recorded by the Dutch Child hood Leukaemia Study Group (DCLSG, set up in 1972) and by nine regiona l cancer registries which together form the Netherlands Cancer Registr y (NCR, set up in 1989). The data files from the incidence years 1989- 1992 of the two registries were linked in order to evaluate accuracy a nd completeness and to calculate and equalise the incidence rates for childhood leukaemia in The Netherlands. Unlinked records or records wi th disagreements (birth date, sex, type of leukaemia and incidence dat e) were checked by the DCLSG and by the regional cancer registries. Th e DCLSG recorded 431 cases of childhood leukaemia, while the NCR recor ded 434 cases. After record linkage and review of the cases, it was co ncluded the 445 records should have been recorded as childhood leukaem ia. The NCR had recorded 425 of the 445 correct cases (95.5%), but had missed 20 cases (4.5%). The DCLSG had recorded 431 of the 445 correct cases (96.9%) and had missed 14 cases (3.1%). In addition, the NCR ha d recorded 9 cases incorrectly as childhood leukaemia. Part of the dis agreement was caused by differences in coding rules (definition of non -Hodgkin's lymphoma (NHL) and the myelodysplastic syndrome versus leuk aemia). It could be concluded that the quality and completeness of the two registries was very high. Regular comparison of the recorded data will help to reveal the inherently problematic disagreement between d efinitions and coding. (C) 1997 Elsevier Science Ltd.