Agreement between the Danish Cancer Registry and the Danish Colorectal Cancer Group Database.

Background: The Danish Cancer Registry (DCR) and the Danish Colorectal Cancer Group (DCCG) database are population-based registries collecting information on Danish patients with colorectal cancer (CRC). DCR registers all patients with incident CRC whereas DCCG records patients with first time CRC. The registries use different inclusion criteria. The consequencenses of this are unknown and not previously evaluated. The aim of this study was to examine the agreement between patients registered in DCR and DCCG and to evaluate its influence on estimated survival and mortality.Material and methods: Patients registered in DCR and DCCG with CRC in 2014-2015 were included. Because of different inclusion criteria, DCCG's inclusion criteria were applied to DCR. Descriptive statistics were used for comparisons. One-year relative survival (1-year RS) was calculated, and the Cox proportional hazard model used for calculating 1-year mortality rate ratios (1-year MRR).Results: In 2014-2015, DCR registered 9678 Danish residents with CRC that fulfilled DCCG's inclusion criteria, while DCCG registered 10,312 Danish residents with CRC. Allowing ±180 days between dates of diagnosis, 10,688 patients were registered with CRC in the merger of the two registries. Of these, 86% were included in both registers, 4% only in DCR, and 10% only in DCCG. No difference was found in 1-year RS between patients in DCR 86% (95% CI: 85-87) and DCCG 85% (95% CI: 84-86). However, patients registered in DCCG had a 1-year MRR of 1.09 (95% CI: 1.01-1.17) compared to DCR.Conclusion: An agreement of 86% of patients was found between the two registries. The discrepancy did not influence 1-year RS. DCCG registered more patients than DCR, and 1-year MRR of patients in DCCG was increased compared to patients in DCR. Regular linkage of the registries is recommended to improve data quality of both registries.

Agreement between the Danish Cancer Registry and the Danish Lung Cancer Registry.

INTRODUCTION: The Danish Cancer Registry (DCR) and the Danish Lung Cancer Registry (DLCR) are nation-wide registries recording Danish patients with lung cancer (LC). The aim of this study was to assess data agreement and possible consequences hereof on estimation of survival between patients in the two registries. METHODS: Descriptive statistics were used for comparison of registered patients in 2013-2014 in the DCR and the DLCR. Furthermore, the one-year relative survival (1y-RS) and Cox proportional mortality hazard rates (MRR) were calculated. RESULTS: In 2013-2014, a total of 9,111 Danish residents were identified with LC in the DCR and 9,316 were found in the DLCR. Merging the two registries showed an agreement of 87%, whereas 6% were included only in the DCR and 8% only in the DLCR. Including patients only registered in one registry, but who seemed to meet the inclusion criteria of both registries, would increase the agreement to 95%. No differences were seen for 1y-RS. However, MRR for patients in the DLCR was significantly lower than for patients in the DCR: 0.94 (95% confidence interval: 0.91-0.98). CONCLUSIONS: Surprisingly, the DCR registered fewer patients in 2013-2014 than the DLCR, even though they employ the same primary data source. The agreement between the DCR and the DLCR was 87%; this may be increased to 95% if patients who seemed to meet the inclusion criteria of the other register were also included. The discrepancies found were mainly due to different definitions of dates of diagnosis, registrations probably missed by the algorithms and possible registration errors. Discrepancies resulted in a significant difference in MRR, but not in 1y-RS. FUNDING: none. TRIAL REGISTRATION: not relevant.