The importance of redistribution process of ill-defined deaths in national mortality database.

Causes of death (CoDs) statistics are an important source of information for epidemiological research. Some causes of death (CoDs) are not regarded as sufficiently specific causes of death for public health purposes, they are named "ill-defined deaths" (IDDs) or "garbage codes". Redistribution is the process of reallocating IDDs to plausible underlying causes (i.e., target cause) as defined in the Global Burden of Disease (GBD) study. The main objectives of this commentary were to describe the various steps taken for the redistribution of IDDs by applying the Belgium redistribution approach to national mortality data sets and to underline key challenges with potential solutions.A four-step probabilistic redistribution method was developed in the context of the Belgian national Burden of Disease (BeBOD) study including followings: (1) predefined ICD codes, (2) package redistribution using multiple causes of death data (MCOD), (3) internal redistribution, and (4) redistribution to all causes. The Belgian, French and Slovenian mortality databases included a share of 34%, 36% and 20% of IDDs in 2017, respectively. The majority of the IDDs were redistributed using predefined ICD-10 codes (14%), followed by package redistribution using MCOD data (11%) in Belgium and French database, whereas this redistribution was 7% and 10% for Slovenia database, respectively. The main challenges encountered were lack of computational capacity to run 100 simulations and lack of MCOD.This commentary highlighted the importance of the harmonized approach of redistribution that allowed us to get an in-depth knowledge of various steps applied for the redistribution process transparently and allowed comparing these results with other European countries. Further research is recommended considering creating a common/standardized consensus list of IDDs based on a comprehensive definition and aligned with the context of national mortality databases in European countries.