03 · What You Need to Know
Deciding Which Contact Information to Collect at Enrollment
Why Baseline Is an Important Point for Contact Planning
Baseline enrollment provides an opportunity to explain how follow-up will work before participants begin the study.
Researchers can describe the expected duration, assessment schedule, communication methods, and procedures for updating contact information.
Participants can then make informed decisions about which contact channels they are willing to authorize.
Collecting an appropriate alternative method at baseline may be more reliable than trying to obtain one after the primary channel has stopped working.
However, the baseline process should not become an opportunity to collect every identifier that might conceivably be useful.
The information requested should reflect foreseeable follow-up needs and the principle of data minimization.
Alternative Contact Methods Are Not All Equivalent
Researchers may consider several types of contact information, each with different advantages and risks.
| Contact method |
Potential use |
Important consideration |
| Personal email address |
Communication after leaving an institution |
Account security, shared access, and participant preferences |
| Second telephone number |
Alternative direct contact when the primary number changes |
Number ownership, reassignment, and message confidentiality |
| Messaging application |
Communication through a participant-preferred platform |
Platform privacy, account visibility, and institutional authorization |
| Postal address |
Mail-based follow-up or correspondence |
Residential mobility and disclosure to household members |
| Third-party contact person |
Potential assistance in reconnecting with an unreachable participant |
Separate privacy, authorization, disclosure, and safety concerns |
No method is universally most stable or secure.
For example, personal email may be useful for graduating students, while telephone communication may be more accessible in some community settings.
The selection should reflect actual participant circumstances rather than assumptions about which technology everyone uses.
Distinguish Direct Alternatives From Third-Party Contacts
A direct alternative contact method allows researchers to communicate with the participant through another authorized channel.
A third-party contact involves another person, such as a relative, friend, or trusted individual, who may be asked to assist with reconnecting.
Direct alternative contact
An additional communication method controlled or authorized by the participant for receiving study communications.
Third-party contact
Information about another individual who may be approached under specifically authorized circumstances to assist with locating or contacting the participant.
These arrangements should not be treated as interchangeable.
Collecting a participant's second email address generally raises different issues from collecting the name and telephone number of someone who has not independently enrolled in the study.
Third-party contact may reveal research participation or sensitive information. It may also create risks when the participant's relationships or living circumstances change.
Researchers should establish a specific ethical and legal basis before collecting or using such information.
Data Minimization Should Guide Collection
Data minimization means limiting personal information to what is adequate, relevant, and necessary for a specified purpose.
This principle appears in major data protection frameworks, including the European Union's General Data Protection Regulation and the Philippines' Data Privacy Act framework.
Researchers should therefore ask what each proposed contact field contributes to the study.
For example, a short follow-up study may not need a residential address when participants can reliably receive an approved electronic questionnaire.
Likewise, collecting multiple telephone numbers may be unnecessary if participants have already provided a suitable primary and alternative communication method.
The aim is not to minimize data at the expense of necessary follow-up. It is to justify collection in relation to a defined purpose and avoid retaining information without a legitimate need.
Consent and Privacy-Law Authorization Are Related but Distinct
Researchers should explain how contact information will be used and obtain the permissions required by the applicable research ethics and legal frameworks.
However, consent to participate in research and the lawful basis for processing personal data are not always identical concepts.
For example, under the GDPR, research participation consent does not automatically establish that consent is the appropriate legal basis for every associated data-processing activity. Other lawful bases and safeguards may apply depending on the circumstances.
Similarly, researchers operating in the Philippines must consider the Data Privacy Act of 2012, its implementing rules, and relevant guidance from the National Privacy Commission.
The appropriate legal basis, transparency requirements, and safeguards depend on the institution, information collected, and processing activities.
Researchers should consult their institutional privacy and ethics personnel rather than assuming that a signed research consent form resolves every data protection obligation.
Participants Should Understand How Each Contact Method Will Be Used
Providing a contact detail does not necessarily mean that participants expect researchers to use it for every purpose.
The baseline explanation should clarify which method will be used routinely and under what circumstances an alternative may be used.
For example, a participant might authorize email for ordinary assessment invitations and telephone contact only when an appointment requires rescheduling.
Another participant may prefer text messages but not voice calls.
Researchers should document preferences when appropriate and avoid using an alternative channel in ways that contradict the participant's expressed choices.
Participants should also understand how to update their preferences and request that further routine communication stop.
Alternative Contact Collection Should Reflect Study Duration
The expected follow-up period is an important consideration.
A study involving one questionnaire two weeks after baseline may have limited need for several contact methods.
A study following participants for three years may face a greater likelihood of changes in residence, employment, institutional affiliation, or communication access.
However, longer duration does not automatically justify collecting every available identifier.
Researchers should consider the expected mobility of the population, the frequency of assessments, and the feasibility of participant-initiated contact updates.
The objective is to maintain proportionate communication arrangements over the period required by the research.
Institutional Contact Details May Become Unavailable
Institutional email addresses and telephone numbers can be convenient during recruitment.
However, their availability may depend on continued enrollment, employment, or service use.
For example, a student may lose university email access after graduation. An employee may no longer use a workplace account after changing jobs.
If the study continues beyond these transitions, an appropriately authorized personal contact method may be useful.
Researchers should consider whether the participant can be contacted independently of the original recruitment institution.
This is particularly relevant when planning follow-up after participants change locations or contact details.
Alternative Contact Methods Can Create New Privacy Risks
Every additional communication channel introduces possible disclosure risks.
A text message may appear on a shared telephone. A postal letter may be opened by another household member. A messaging application may display the research team's identity or message preview.
These risks may be especially consequential in studies involving sensitive health, employment, family, or personal experiences.
Researchers should consider whether the message content can be minimized and whether the participant has a safe, private way to receive communication.
Where necessary, neutral contact wording may reduce unnecessary disclosure, provided the message remains recognizable and accurate.
Privacy considerations should be assessed for each proposed channel rather than assuming that all electronic communication is equally secure.
Third-Party Contact Requires Additional Safeguards
Some studies involving extended follow-up may consider collecting the details of a person who could help researchers reconnect with a participant.
Such arrangements should not be treated as routine requirements for all participants.
Researchers should consider whether the third party understands the proposed contact, whether the participant has authorized the arrangement, and whether the contact could disclose sensitive information.
In some contexts, contacting relatives or acquaintances could create safety risks or reveal circumstances that participants have chosen to keep private.
Researchers should also define what the third party may be told. A request to pass along a neutral message is different from disclosing the study's sensitive purpose or asking questions about the participant's personal circumstances.
Any third-party procedure should be reviewed under applicable ethics and privacy requirements before use.
Store Contact Information Separately From Research Outcomes Where Appropriate
Contact information is identifiable personal data and should be protected accordingly.
Where practical, researchers can maintain a secure contact database separate from the main analytical dataset.
A coded participant identifier may link contact records to research observations without placing names and telephone numbers in every analysis file.
However, coded information remains potentially identifiable when a linkage key exists. Pseudonymization should not be described as complete anonymization.
Access should be restricted to personnel who need the information for authorized research tasks.
Researchers should also establish appropriate retention periods, secure deletion or archiving procedures, and arrangements for handling updates or corrections.
These requirements should follow the applicable institutional and legal framework.
Do Not Make Unnecessary Contact Information a Condition of Participation
Researchers should distinguish information essential for the study from information that would merely make follow-up more convenient.
For example, requiring every participant to provide a relative's telephone number may discourage individuals who cannot or do not wish to identify another person.
Such a requirement may create an additional selection mechanism unrelated to the research question.
If an alternative contact method is genuinely necessary for the study, the rationale should be explicit and ethically justified.
Otherwise, optional contact preferences may provide a more proportionate approach.
Researchers should avoid excluding eligible individuals merely because they decline to provide unnecessary additional identifiers.
How Should Researchers Verify and Update Alternative Contacts?
Contact details can become outdated or inaccurate.
Researchers may incorporate verification into scheduled assessments or provide a secure participant-initiated update process.
Verification procedures should be proportionate and should not involve contacting third parties or sending sensitive messages without appropriate authorization.
For example, asking participants to confirm their preferred email during a routine follow-up may be less burdensome than repeatedly requesting updates between assessments.
Researchers should also consider how obsolete details will be corrected or removed from active contact systems.
These procedures belong within the study's documented retention strategy.
Alternative Contacts Do Not Guarantee Retention
Collecting additional contact methods may improve the opportunity to reconnect with some participants.
However, a participant may change several contact details simultaneously, become unavailable, or choose not to continue.
Alternative channels may also be ineffective if participants rarely use them or do not recognize research messages.
Researchers should therefore avoid presenting alternative contact collection as a guaranteed solution to attrition.
The potential benefit should be weighed against the additional privacy and administrative responsibilities.
Where appropriate, retention outcomes can be monitored to assess whether the selected arrangements appear useful, although observational comparisons cannot necessarily establish causal effects.
Baseline Contact Planning Should Be Integrated With Follow-Up Frequency
Collecting an alternative method does not establish how often researchers may use it.
The protocol should separately specify contact frequency, reminder limits, and the conditions under which alternative channels become appropriate.
For example, a participant may authorize a second email address as a backup without agreeing to receive duplicate reminders at both addresses.
Researchers should avoid treating the availability of multiple contact channels as justification for more frequent communication.
The planned frequency of follow-up contact should remain proportionate to the assessment requirements and participant preferences.
Watch Out
Do not assume that research consent automatically authorizes collection of relatives' details, social media accounts, residential addresses, or other personal identifiers. Each category of information requires a legitimate purpose, appropriate authorization, and safeguards consistent with the applicable privacy and ethics framework.
