Why enrollment funnels leak and what sponsors and sites should ask about participant identification, screening capacity, and retention
Clinical trial recruitment is an operational problem before it is a marketing problem. When enrollment lags, the root causes are usually process gaps: participant identification that does not scale, pre-screening capacity that is chronically underfunded, and follow-up workflows that do not match participants’ lives. A recent analysis from the USC Schaeffer Institute on Alzheimer’s disease trial recruitment highlights four high-leverage areas: protocol design and site selection, participant identification, funding of pre-screening, and long-term recruitment infrastructure. These are systemic issues. Below we translate those strategic findings into concrete operational questions and communication patterns that sponsors, contract research organizations (CROs), and sites can act on.
Where the funnel breaks in practice
The recruitment pathway is a chain of handoffs: outreach leads to interest, interest needs pre-screening, pre-screening leads to on-site screening, and screening leads to enrollment. Two failure modes appear again and again. First, the candidate pool is overestimated because identification methods are narrow or outdated. Second, pre-screening capacity is underfunded so leads pile up and never reach the screening visit.
Executives should ask their teams: How are potential participants being found and prioritized across channels, including phone outreach to older adults and caregiver networks? Is there dedicated capacity for continuous pre-screening, or is pre-screening treated as an intermittent task that sites bolt on to clinical duties? How quickly do lead responses move from initial contact to a scheduled screening visit, and where do delays cluster?
These questions matter because each enrollee has a unique timeline. Someone who expresses interest on Monday is on a different clock than someone who responds the next month. If a trial treats interest as a single, undifferentiated bucket, the operation will miss windows where a participant is most likely to convert.
Phone-first outreach and what it solves
Phone-first outreach reaches people who do not use smartphone apps, who prefer voice contact, or who rely on caregiver networks. Automated calling and text messaging (SMS) can handle high volumes of initial contacts, capture basic eligibility responses, and route likely candidates to a human screener. That pattern reduces time-to-screen and preserves human effort for the complex cases.
In a working workflow, automated outbound calls or texts invite potential participants to answer a short pre-screen. Those who pass receive a human follow-up for consent and scheduling. Pre-screening scripts are designed to capture the few items that drive screen-failure risk so sites can triage leads before scheduling on-site visits. Reminders and simple longitudinal check-ins keep interested people engaged while the site completes diagnostic steps that cannot be done remotely.
Beyond raw reach, this approach supports retention. Patient-reported outcome (PRO) collection done by voice or SMS is less likely to lose older adults who find apps difficult. The goal is not to replace clinical contact, but to reduce no-shows and failed screens by keeping the participant’s timeline moving forward with low-friction touches.
What to watch for
There are trade-offs and a few common operational pitfalls to avoid. First, automation without clear escalation rules creates more work, not less. If an automated pre-screen flags a concern and there is no staffed pathway to handle it, leads accumulate. Second, multilingual support and caregiver consent channels are not optional for many Alzheimer’s trials. Third, documentation matters. Regulators and Institutional Review Boards (IRBs) will want to see an auditable record of outreach and consent activity, so the communication layer must produce traceable logs.
Practical governance questions for sponsors and sites: Do our protocol and eligibility choices make recruitment harder than necessary? Could relaxation of non-essential criteria expand the reachable pool? Have we budgeted for continuous pre-screening capacity rather than episodic bursts of work? What channels do our target participants prefer, and do our outreach plans include voice and SMS for older adults and caregivers?
If the answers point to gaps, the fix is usually operational, not promotional. Adjusting site selection, funding pre-screening, and adding phone-first, low-friction outreach will move the needle faster than another ad buy. These changes also support the representative enrollment that sponsors say they want because phone-based and multilingual workflows reach populations that app-only strategies miss.
One final note on risk. Communication systems in clinical trials should be HIPAA-aligned and designed to protect participant data. That is part of the table stakes. The system should also integrate with the site’s case management system so data is not siloed and so clinicians see what they need without manual re-entry.
The honest operational takeaway is straightforward. Trial recruitment succeeds when the work of finding, pre-screening, and keeping candidates engaged is funded, measured, and automated where appropriate. Sponsors and sites that treat pre-screening as a core, ongoing function will see fewer wasted visits and faster enrollment.
More on voice-first PRO collection and longitudinal participant workflows is at /innovative-ivr-solutions-healthcare-services/promis-patient-reported-outcomes-measurement-information-system-surveys-phone-and-sms-based.
Related coverage: Fixing the Funnel: Stakeholder Insights on Alzheimer’s Disease Trial Recruitment — USC Schaeffer