Assessment of the investigation of ill-defined causes of death in Brazil in 2010.

Objective: to assess the results of the investigation of ill-defined causes of death (IDCD) to improve the quality of cause-of-death data in Brazil. Methods: this is a descriptive study using data from the Mortality Information System; all IDCD which occurred in 2010 were selected; deaths were analyzed according to macroregions, states, state capitals and characteristics of how the investigations were carried out. Results: the proportion of IDCD was 8.6% in Brazil in 2010 and decreased to 7.0% after investigation and fell from 4.7% to 3.4% in state capitals after investigation; approximately 65% of the investigated cases were reclassified to a defined cause in states and state capitals. Conclusion: there was an improvement in data quality on cause of death resulting from these investigations which have led to an important decrease in the proportion of IDCD in the states and state capitals, although there are still some regional inequalities.