Context A participant death is a serious event in a clinical trial and needs to be unambiguously and publicly reported.

Objective To examine (1) how often and how numbers of deaths are reported in ClinicalTrials.gov records; (2) how often total deaths can be determined per arm within a ClinicalTrials.gov results record and its corresponding publication and (3) whether counts may be discordant.

Design Registry-based study of clinical trial results reporting.

Setting ClinicalTrials.gov results database searched in July 2011 and matched PubMed publications.

Selection criteria A random sample of ClinicalTrials.gov results records. Detailed review of records with a single corresponding publication.

Main outcome measure ClinicalTrials.gov records reporting number of deaths under participant flow, primary or secondary outcome or serious adverse events. Consistency in reporting of number of deaths between ClinicalTrials.gov records and corresponding publications.

Results In 500 randomly selected ClinicalTrials.gov records, only 123 records (25%) reported a number for deaths. Reporting of deaths across data modules for participant flow, primary or secondary outcomes and serious adverse events was variable. In a sample of 27 pairs of ClinicalTrials.gov records with number of deaths and corresponding publications, total deaths per arm could only be determined in 56% (15/27 pairs) but were discordant in 19% (5/27). In 27 pairs of ClinicalTrials.gov records without any information on number of deaths, 48% (13/27) were discordant since the publications reported absence of deaths in 33% (9/27) and positive death numbers in 15% (4/27).

Conclusions Deaths are variably reported in ClinicalTrials.gov records. A reliable total number of deaths per arm cannot always be determined with certainty or can be discordant with number reported in corresponding trial publications. This highlights a need for unambiguous and complete reporting of the number of deaths in trial registries and publications.