CT.gov Completion Cohort Debt

Abstract

It is not clear whether ClinicalTrials.gov data become more complete when studies are given two years to report. Using 249,507 older, already-closed eligible studies from a March 29, 2026 snapshot, we analysed and grouped them by primary completion year and completion era. Using data on ghost protocols and two-year no-results rates, we carried out the analysis. The 2008 to 2012 era showed a 64.4 percent no-results rate and a 38.8 percent ghost-protocol rate. However, from 2021 to 2024 this worsened to 77.0 percent and 46.7 percent respectively, with only a 10.8 percent fully visible share. This has been consistent year on year, which shows that eligibility does not reduce registry silence. These cohort comparisons are descriptive and uneven, reflecting changing trial mix and reporting behaviour.