CT.gov Outcome-Density Gap

Paper

Does richer outcome specification correspond to a more visible CT.gov record once older closed interventional studies are grouped by outcome density? We analysed 249,507 eligible older closed interventional studies from the March 29, 2026 full-registry snapshot and bucketed primary outcomes, secondary outcomes, and primary-outcome description fields. The project compares two-year no-results rates, ghost-protocol rates, full visibility, and description contrasts across sparse and dense outcome structures. Studies with zero recorded primary outcomes show a 100.0 percent no-results rate and a 65.1 percent ghost-protocol rate. Studies with ten or more secondary outcomes fall to 56.7 percent no results, while studies missing primary-outcome descriptions still reach 94.4 percent no results. Outcome density therefore looks like a proxy for public record seriousness: sparser protocols are far more likely to remain hidden. The gradient survives across counts, text fields, and both primary and secondary outcome layers. Outcome counts capture declared registry structure rather than scientific importance, statistical hierarchy, or endpoint quality.