Deterministic linkage for improving follow-up time in a Brazilian population-based cancer registry

Population-based cancer registries (PBCR) are the primary source of cancer incidence and survival statistics. The loss to follow-up of these patients is concerning since it reduces the reliability of any statistical analysis. The linkage techniques have been increasingly used to improve data quality in various information systems. The linkage was performed between the databases of the PBCR-Barretos and the mortality database of the state of São Paulo. To evaluate the improvement in the follow-up time of patients, the comparability of the two databases, pre- and post linkage, was made. Three analyses were performed: a comparative analysis of the absolute number of deaths, a comparative analysis of the follow-up time of patients and the survival analysis. After linkage, there was an increase of 813 deaths. The follow-up time of patients was extended and observed in most types of tumours. The comparability of the survival analyses at both time points also showed a decrease in survival probabilities for all tumour types. Deterministic linkage is effective in updating the vital status of registered patients, improving patient follow-up time, and maintaining good quality data from PBCRs, consequently producing more reliable rates, as seen for the survival analyses.