CT.gov Structural Missingness: Field-level information loss across the full ClinicalTrials.gov registry

Abstract

What information disappears from ClinicalTrials.gov even before one asks whether the results were posted? We analysed the 12 April 2026 full-registry snapshot and quantified structural missingness in publication links, IPD statements, detailed descriptions, locations, and outcome fields. The source universe comprised 579,828 studies, allowing field-level omission rates and sponsor-specific sparsity patterns to be estimated without sampling. Across the full registry, 62.9 percent of records lacked publication links, 48.2 percent lacked IPD sharing statements, 32.8 percent lacked a detailed description, and 10.2 percent lacked locations. Structural sparsity was unevenly distributed: industry records were the most affected overall, NIH had the highest missingness of IPD sharing statements, and records carrying no sponsor class reflected malformed metadata. This missingness extends beyond results reporting into the descriptive fields needed for interpretation, replication, and scrutiny, leaving less context for appraisal, accountability, and public oversight. These metrics capture registry-visible information loss rather than proven intent to conceal.