Disentangling Uncertainty from Evidence Validity in Clinical Trial Screening

Selective clinical trial screening has two independently observable events: whether an eligibility label is decisive and whether its cited evidence was available, patient-bound, and intact at the protocol cutoff. ActAudit represents these events separately: automatic action requires both a singleton split-conformal set and deterministic source, time, patient, span, and integrity checks over a nonempty citation set. To identify the contribution of each condition, the evaluation fixes every retrieved-evidence and label-score tuple and changes only the routing policy. On 21,073 grouped-holdout patient–criterion pairs, nearly equal-coverage policies (67.2% versus 67.3%) yield 0.40% versus 1.27% false-eligible (FE) risk and 0 versus 11 post-cutoff citations. Removing evidence validity from the identical conformal threshold adds 3.4 coverage points, 0.31 FE points, and 14 post-cutoff citations; removing singleton uncertainty adds 12.3 coverage points and 1.31 FE points. Across five prespecified operating points, the joint rule retains at least a 0.65-point nearest-coverage FE advantage over scalar confidence, and frozen transfer to 6,240 FHIR-native pairs reproduces the separation (0.61% versus 1.68% FE). Evidence removal also changes the label or forces deferral for 88.3% of audited note-dependent actions. The results establish structural evidence validity as an independently measurable determinant of selective action in the evaluated clinical cohorts.