A participant misses a scheduled visit. Then a telephone call goes unanswered. An email bounces back, and a letter is returned as undeliverable.
At what point can the study team say the participant is lost to follow-up?
There is no universal number of missed visits, unanswered calls, or returned letters that automatically determines lost-to-follow-up status in every clinical trial. The answer usually depends on the protocol, informed consent form, sponsor instructions, site procedures, applicable privacy requirements, and the information the study still needs.
After handling more than 25,000 LTFU-related requests, OmniTrace has learned that the problem is not always a lack of effort. Sometimes the contact log is lengthy, but every attempt relies on the same outdated telephone number, email address, or mailing address. Repeating an unsuccessful method does not necessarily produce a meaningful search.
A Missed Visit Does Not Automatically Mean Lost to Follow-Up
People miss study visits for many reasons. They travel, change telephone numbers, move, experience family emergencies, or simply forget. A voicemail box may be full. An email address may no longer be used. Mail may be returned because the participant moved without updating the study site.
The practical question is whether the study team has made reasonable, properly documented efforts through the methods authorized for that study and still cannot determine the participant’s status.
It is also important to separate three different questions:
- Can the site communicate with the participant?
- Can the participant’s current location or vital status be determined?
- What information does the study actually need?
A participant may be unreachable through the site’s existing contact information but still be locatable through professional research. Locating the participant also does not mean that the person has agreed to resume visits or continue participating in the study.
When Is a Participant Considered Lost to Follow-Up?
A participant may generally be considered lost to follow-up when the study team can no longer reach the person, or otherwise obtain the required follow-up information, after completing the efforts required by the protocol and related study procedures.
Published procedures vary. Some organizations use a defined number of calls followed by written correspondence. Certain long-term oncology studies may require several documented contact strategies and an extended period without vital-status information before formally classifying a participant as lost to follow-up.
These are study- or institution-specific procedures, not universal rules.
A short study with frequent visits may handle missed contact differently from a long-term outcomes study that follows participants for several years. A study involving an important safety or survival endpoint may require a different level of follow-up from one in which the missing information is less critical.
The LTFU process should therefore be established before participants begin disappearing. The study documents should address:
- What triggers enhanced follow-up efforts
- Which contact methods are permitted
- What level or duration of effort is expected
- Whether approved secondary contacts may be approached
- Whether professional location or vital-status research may be used
- Whether a locator may conduct research only or also contact the participant
- Who decides that routine site efforts have been exhausted
- How the efforts and outcome will be documented
Without a defined process, different sites may handle similar situations in very different ways.
How Many Contact Attempts Are Enough?
This is one of the questions we hear most often. The honest answer is that no single number works for every clinical trial.
Three telephone calls may satisfy one study’s written procedure and be inadequate under another. More importantly, repeated calls to an outdated or reassigned number do not necessarily amount to a serious locating effort.
The more useful question is whether the attempts used current information, different authorized channels, reasonable timing, and a defined escalation process.
A practical review should ask:
- Were all permitted contact methods used?
- Was the contact information checked for errors or signs that it was outdated?
- Did returned mail provide forwarding or other useful information?
- Were approved secondary contacts available?
- Did the participant previously mention a move, travel, or change in circumstances?
- Is there reason to research whether the participant may be deceased?
- Does the study permit professional location or vital-status research?
- Was the matter escalated when routine efforts stopped producing new information?
The purpose is not to generate a large contact log. It is to make a reasonable, organized, and documented effort using the methods the study has authorized.
Routine Site Outreach and Professional Location Research Are Different
Routine site outreach may include approved telephone, electronic, written, portal, and secondary-contact methods. These efforts generally rely on information already held by the site.
Professional location research begins at a different point. It may involve:
- Researching updated addresses or telephone numbers
- Identifying evidence that a participant has relocated
- Resolving incomplete or conflicting identifying information
- Researching name changes
- Conducting vital-status research
- Identifying a recent “alive as of” date
- Researching date-of-death information
- Obtaining a death certificate when authorized and available
- Coordinating consistent searches across multiple sites or countries
Not every method is appropriate or permitted in every trial. The fact that information can be found does not automatically mean that it can be used for every purpose.
The protocol, informed consent language, privacy requirements, sponsor instructions, and applicable IRB or ethics committee approvals should define the boundaries. This is especially important when deciding whether a professional locator will provide findings to the study team or contact the participant directly.
What Should the Study Team Document?
A follow-up effort can be reasonable and still become difficult to evaluate if it was poorly documented.
A brief notation stating “unable to locate participant” does not explain whether meaningful due diligence occurred.
Depending on the study, the record may need to show:
- The date and method of each attempt
- The telephone number, email address, or mailing address used
- When that information was last known to be valid
- Whether a voicemail was left
- Whether an email bounced
- Whether mail was returned
- Whether a telephone number was disconnected or reassigned
- Whether an approved secondary contact was approached
- What response or new information was received
- When and why the matter was escalated
- Who authorized additional research
- What result was requested
- What information was returned
- How the case was closed
- The basis for the participant’s final study status
Documenting activity is not the same as documenting due diligence. The record should show not only how often the site tried, but whether the information and methods being used were still meaningful.
Current Good Clinical Practice guidance also emphasizes that trial-related activities assigned to service providers should be clearly allocated and documented, with appropriate oversight and attention to participant privacy and data reliability.
Lost to Follow-Up Is Not the Same as Withdrawal
Silence is not withdrawal.
A participant who withdraws has communicated a decision about continued participation. A participant who is lost to follow-up has generally become unreachable, leaving the study team unable to confirm the person’s intentions or current status.
There may also be important differences between:
- Stopping the investigational treatment
- Declining additional study visits
- Withdrawing from certain study procedures
- Agreeing to limited safety or survival follow-up
- Withdrawing from further follow-up
- Becoming unreachable without communicating any decision
A participant may stop taking the investigational product but agree to continued follow-up. Another participant may decline further visits but permit the collection of limited outcome information. Someone else may simply stop responding without ever expressing a desire to withdraw.
The study team should not assign an affirmative decision to a participant who never communicated one.
FDA guidance also distinguishes withdrawal from the interventional portion of a study from continued follow-up. In the United States, if a participant does not consent to continued follow-up, an investigator generally may not access medical or other confidential records that require the participant’s consent for study purposes. Previously collected study data may be retained, however, and public records may be consulted, including records establishing survival status.
Before Referring an LTFU Case, Define the Assignment
“Find the participant” is often too vague to serve as a useful project instruction.
Before an outside search begins, the sponsor, CRO, or study team should define what it actually needs. The objective may be:
- Updated contact information returned to the site
- A current mailing address or telephone number
- Vital-status confirmation
- A recent “alive as of” date
- Date-of-death information
- A death certificate
- Research only, with no direct participant contact
- Direct contact under an approved process
- A coordinated multisite or multinational search program
The assignment should also answer several practical questions:
- Who is authorized to provide participant information to the locator?
- What identifying information will be supplied?
- Who should receive the results?
- May the locator contact the participant, or must all contact come from the site?
- What study documents and privacy requirements govern the work?
- Are there country-specific restrictions?
- Is there a database lock, safety-reporting deadline, or other important milestone?
- How should an inconclusive search be documented and closed?
Defining these points at the beginning reduces confusion, prevents unnecessary research, and helps the locator return information in a form the study can actually use.
When Should a Professional Patient Locator Be Involved?
A professional locator should not replace ordinary site follow-up. It becomes useful when routine methods have failed or the existing information is no longer producing meaningful leads.
Common signs include disconnected or reassigned telephone numbers, returned mail, outdated or conflicting information, possible relocation or name changes, unknown vital status, multiple unresolved cases across study sites, or an approaching database lock or other important milestone.
Earlier escalation can sometimes be more productive than waiting until every available piece of contact information is years out of date. That does not mean referring every missed visit immediately. It means recognizing when continued repetition of the same site methods is unlikely to produce a different result.
What OmniTrace Brings to an LTFU Assignment
OmniTrace supported its first clinical study in 2003 and has since handled more than 25,000 LTFU-related requests. Our work has included updated contact-information research, vital-status research, “alive as of” reporting, date-of-death research, death-certificate retrieval, informed consent language review, site communications, and LTFU training. Services are available in more than 50 countries.
The workflow depends on the study. In some assignments, OmniTrace performs research and returns updated information to the site without contacting the participant. In others, direct contact may be permitted under an approved process. A single-site referral may be handled differently from a large program involving hundreds of participants and sites.
In one published OmniTrace case study, a pharmaceutical company referred 443 LTFU participants from 208 sites. The assignment was to update contact information and return the findings to the sites. OmniTrace reported locating 91% of the referred participants.
That result does not guarantee the same outcome in another study. It does illustrate the difference between repeatedly using stale site information and conducting a coordinated professional search.
The Practical Answer
A participant is not automatically lost to follow-up after one missed visit or a fixed number of unanswered calls. The status should reflect the study’s approved requirements, the importance of the missing information, the methods that were attempted, and whether those efforts were meaningful and properly documented.
Lost to follow-up cannot always be prevented. Clear procedures, accurate documentation, appropriate informed consent language, and timely escalation can give the study team more options when it occurs.
Frequently Asked Questions
What information should a site provide to a professional locator?
The specific information depends on the approved workflow and applicable privacy requirements. It commonly includes enough accurate identifying information to distinguish the participant from other people with similar names, the last known contact information, the date that information was last verified, and the result being requested. Only information appropriate and authorized for the assignment should be transferred.
Does locating a participant necessarily mean contacting the participant?
No. In many assignments, the locator conducts research and returns updated information to authorized study personnel. Direct contact by a locator should occur only when it is permitted by the approved study process.
Can public records be used to research survival status after withdrawal?
In the United States, FDA guidance states that an investigator may consult public records, including those establishing survival status, even when a participant who has withdrawn does not consent to continued collection of information from medical or other confidential records. The approach should still be reviewed against the study documents and applicable requirements.
Can a participant be found after being classified as lost to follow-up?
Yes. A participant may still be located after moving, changing telephone numbers, changing names, or losing contact with the original site. An administrative LTFU classification does not mean that a professional search cannot produce updated information.
For help planning or conducting lost-to-follow-up participant searches, contact OmniTrace at (800) 799-1911.
