Croatia secondary and future use consent requirements

Decide whether the main consent is enough

Mandatory protocol use. If a sample or data analysis is required for the trial and fully described in the protocol, explain it inside the unified main informed consent. State the purpose, sample type and volume, tests, processing, storage location, storage period, access, transfer, return of results, and end-of-trial handling.

Optional substudy. If pharmacogenetic, biomarker, imaging, digital, or other research is optional and a participant can join the main trial without it, prepare a separate informed consent. Refusal must not affect main-trial participation.

Repository or biobank donation. If samples are collected for undefined future research, use a separate informed consent for donation to the repository or biobank. Croatian national specifics also refer to a permit for storing and using samples for further research based on that separate consent.

Research outside the protocol. Before starting any additional study not described in the approved protocol, obtain a Central Ethics Committee opinion and approval. The committee decides whether the documentation must be supplemented with additional informed consent.

Biological-sample information

Croatian law requires potential participants to be informed about future sample use, the person responsible for collection, the storage location, and what happens to samples after the clinical trial. The national specifics also ask the protocol to state how, where, and how long every sample will be stored and where it will be processed.

The participant document should state:

• the sample type, quantity, collection schedule, and immediate trial purpose
• whether participation in the sample activity is required or optional
• who collects, controls, processes, and receives the samples
• the named laboratory, repository, or storage location where available
• the coding or anonymisation method and whether re-identification remains possible
• storage duration and the event that ends storage
• permitted diseases, research areas, tests, and users
• transfer outside Croatia or the European Economic Area and applicable safeguards
• whether commercial organisations may use samples or results
• whether results or important findings may be returned
• how to withdraw and what happens to unused samples, derived data, and completed analyses
• disposal or other final handling

Do not call samples anonymous if a code and re-identification key remain. Croatian national specifics say repository samples should be stored and processed so they cannot be linked to the participant. Describe the actual method accurately and reconcile it with any withdrawal promise.

Genetics, genome, and exome sequencing

Conditional. Prepare a separate Croatian informed consent for genetic testing of known biomarkers and for complete DNA, whole-genome, or whole-exome analysis as described in the national specifics. Define who can access genetic information, how it will be used, how family implications are handled, and whether clinically important findings may be returned.

Give the participant a clear option not to receive genetic findings. Explain limits of interpretation, confirmation, counselling, and whether findings enter the medical record. Do not promise individual results when the protocol does not support valid return.

If a genetic analysis is mandatory and integral to the main trial, its information belongs in the unified main informed consent. If it is optional, use a separate document and separate DA and NE choices.

Future research and later ethics review

Croatian guidance recognises that a sponsor may not be able to recontact participants many years later. For long-stored samples intended as a future research resource, the guidance may accept that a new participant consent is not sought for each later study if the sponsor or applicant has committed to obtain Central Ethics Committee approval before conducting research not defined in the original protocol.

This does not remove the need for an appropriate initial repository or future-use consent where samples are collected for that purpose. It also does not authorise unrestricted research. Define the original permission, storage, governance, and withdrawal clearly, then obtain the later ethics approval before each out-of-protocol project.

The Central Ethics Committee does not accept taking blood or DNA without a defined use and timeframe while disclaiming any obligation to conduct the stated analysis. If the sponsor wants broader future research, use the repository or biobank pathway rather than vague trial wording.

Data-related secondary use

If participant data will be used beyond trial analysis, safety, regulatory records, or another purpose already described in the approved trial, explain the new scientific purpose, data categories, controller, recipients, retention, coding, transfers, safeguards, and participant rights.

Croatian national specifics require additional Central Ethics Committee approval for scientific use of participant data outside the procedures planned in the protocol. The committee may require supplementary participant consent.

Keep trial consent and data-protection legal bases conceptually separate. Informed consent authorises trial participation and optional research choices. The data controller must also identify a valid legal basis under the General Data Protection Regulation for each processing purpose.

Withdrawal of optional consent

State how the participant withdraws optional sample or data permission and whom to contact. Explain what can be destroyed, anonymised, or no longer used and what cannot be reversed after samples have been consumed, results generated, data anonymised, or research completed.

Do not imply that withdrawing optional research consent means withdrawing from the main trial. Do not make continued standard trial participation conditional on allowing future research.

For minors, the parent or representative may initially consent to storage and future use, while the child provides age-appropriate assent. Croatian guidance requires the participant's own consent for continued storage and use when the participant becomes an adult and gains legal capacity. The Croatia minor consent and assent guide explains the transition.

Sharing, transfer, and governance

Identify who may receive samples and data, including sponsor laboratories, academic collaborators, commercial partners, repositories, and service providers. State whether recipients receive coded or anonymised material and whether onward sharing is permitted.

For transfers outside the European Economic Area, explain the destination categories and safeguards in participant-facing language. Avoid asking for unlimited worldwide transfer without describing governance and protection.

The Part II biological-sample compliance statement, protocol, informed consent, privacy information, material-transfer arrangements, and laboratory plan must all describe the same uses and safeguards.

Croatia-specific final checks

• Protocol-required and optional activities are separated.
• Optional substudies and repository donation have separate Croatian consent where required.
• Samples have a stated purpose, storage location, duration, governance, and final handling.
• Research outside the protocol cannot start without Central Ethics Committee approval.
• Genetic access, use, return of findings, family implications, and right not to know are addressed.
• Withdrawal is practical and does not promise impossible retrieval after anonymisation or completed analysis.
• Participants enrolled as minors are re-consented for continued storage and use at adulthood.
• Data and sample transfer language matches the actual recipients and safeguards.
• The main consent, optional consent, protocol, and Part II compliance statement are consistent.

Use the Croatia patient-facing document QC checklist for the final cross-document review and return to the Croatia CTIS hub for the complete guide cluster.