Screen failure occurs when an individual who has consented to screening procedures is subsequently determined not to meet the eligibility requirements for study participation. This determination may result from laboratory values outside specified ranges, disease characteristics not meeting inclusion criteria, concurrent medications or conditions specified as exclusions, or any other protocol-defined criterion that precludes enrollment. Screen failure represents a normal and expected aspect of the participant selection process.

Screen failure rates vary substantially depending on the therapeutic area, study design, and specificity of eligibility criteria. Complex protocols with numerous inclusion and exclusion criteria typically generate higher screen failure rates than simpler designs. Studies requiring specific disease stages, biomarker profiles, or prior treatment histories may screen many patients to identify eligible enrollees. Understanding expected screen failure rates is essential for enrollment planning, as sites must screen proportionally more patients to achieve enrollment targets when screen failure rates are high.

Analysis of screen failure reasons provides valuable operational intelligence. High screen failure rates due to a specific criterion may indicate that the criterion is more restrictive than anticipated, potentially warranting protocol amendment. Screen failures concentrated at particular sites may reveal differences in prescreening practices or patient population characteristics. Individual review of screen failures helps identify instances where eligible patients may have been inappropriately excluded and ensures that eligibility determinations are made consistently across sites.