Quality and completeness improvement of the Population-based Cancer Registry of São Paulo: linkage technique use.

Objective:: The aim of this study was to improve the quality of information and data completeness through probabilistic and deterministic record linkage between Population-based Cancer Registry of São Paulo (PBCR-SP) for incident cancer cases, death database and drugs/medical procedures database.

Methods:: We used the database of the PBCRP-SP composed of 343,306 incident cancer cases in the municipality of São Paulo in the period between 1997 and 2005 with ages raging from under 1 to 106 years old, from both sexes. Three databases were used for linkage, namely Improvement Program for Mortality Information in São Paulo city (PRO-AIM), Authorization of Procedures of High Complexity/Cost of Outpatient Information System from the Unified Health System (APAC-SIA/SUS), and Foundation State System of Data Analysis (Foundation SEADE). Crude incidence (CIR) and mortality rates (CMR) were calculated and overall survival analysis was performed using the Kaplan-Meier method.

Results:: After record linkage, it was possible to observe gain of 4.3% for the CIR and 25.8% for CMR. The overall survival analysis showed that before record linkage there was an underestimation of the probability of being alive for all variables (p < 0.001).

Conclusion:: The linkage techniques contributed with the improvement of the quality of RCBP-SP information both on completeness of data, as in defining the vital status of the patient. In addition, the results found in this study reflect the ability of databases when worked jointly, providing subsidies for various types of studies and information for planning policies and strategic actions.