[Impact on tuberculosis incidence rates of removal of repeat notification records]

To evaluate the impact on tuberculosis (TB) incidence rates of removal of improper duplicate records from the notification system.

Data from the Sistema de Informação de Agravos de Notificação (Brazilian Information System for Tuberculosis Notification) from 2000 to 2004 were analyzed. Repeat records were identified through probabilistic record linkage and classified into six mutually exclusive categories and then kept, combined or removed from database.

Of all TB records, 73.7% had no duplicate, 18.9% were duplicate, 4.7% were triplicate, and 2.7% were quadruplicate or more. Of all repeat records, 47.3% were classified as transfer in/out; 23.6% return after default, 16.4% true duplicates, 10% relapse, 2.5% inconclusive and 0.2% had missing data. These proportions were different in Brazilian states. Removal of improper duplicate records reduced TB incidence rate per 100.000 inhabitants by 6.1% in the year 2000 (from 44 to 41.3), 8.3% in 2001 (from 44.5 to 40.8), 9.4% in 2002 (from 45.8 to 41.5), 9.2% in 2003 (from 46.9 to 42.6) and 8.4% in 2004 (from 45.4 to 41.6).

The study results indicate that the observed tuberculosis incidence rates represent estimates that would be closer to the actual rates than those obtained from the raw database at state and country level. The use of record linkage approach should be promoted for better quality of notification system data.