ISO 10993 Biological Evaluation Strategy Guide

Start With the Current Framework and the Target Market

ISO 10993-1:2025 is the current international edition. It frames biological safety within risk management and is aligned with the broader process in ISO 14971:2019. It does not turn device categories into automatic test batteries. The evaluation still has to identify hazards, estimate biological risks, control those risks, and judge whether residual risk is acceptable for the intended use.

Market context matters. FDA's September 2023 final biocompatibility guidance remains an essential US submission reference. FDA has partially recognized the 2025 edition, with stated exclusions and a transition during which declarations of conformity to the 2018 edition may be accepted until July 1, 2029; the exact conditions are recorded in FDA's recognition entry. For EU submissions, Annex I and Annex II of the consolidated Medical Device Regulation (EU) 2017/745 make the wider risk-control and technical-documentation context relevant. A global strategy may share one scientific core, but it should explicitly identify market-specific expectations and version assumptions.

Step 1: Define the Device and Its Exposure

Freeze the evaluation unit before debating endpoints. Record intended purpose, patient population, anatomical contact, frequency, cumulative duration, reusable life, accessories, variants, and the configuration delivered to the user. Consider direct contact and indirect contact through a fluid or gas path. A component that never touches tissue can still influence exposure if substances pass from it to the patient.

Contact duration should reflect actual exposure, not simply the duration of one procedure. Repeated exposures may need a cumulative assessment. The device description should also distinguish the marketed configuration from a family representative, test coupon, or earlier version. Without that distinction, apparently relevant evidence can become difficult to apply.

Step 2: Build the Full Material and Process Story

Map every patient-contacting or indirectly contacting component to its material formulation, supplier or grade, colorant, coating, adhesive, joining method, processing aid, cleaning step, sterilization method, packaging contact, and relevant manufacturing site. The biological question concerns the final finished device—not a raw polymer name in isolation.

• Construction map: connect each component to its contact route and exposure duration.
• Material identity: capture grade-level information and additives where available, while controlling confidential supplier data appropriately.
• Process inputs: include mould-release agents, lubricants, cleaning residues, curing agents, inks, bonding materials, and sterilant residues where relevant.
• Change history: compare formulation, supplier, geometry, surface finish, process, packaging, and sterilization against the version supported by existing evidence.

A Practical Strategy Map

The table below is a planning aid, not a substitute for the applicable standards or device-specific regulatory requirements. Its purpose is to make each decision, input, and output visible before testing is commissioned.

Step 3: Use an Evidence Hierarchy, Not an Evidence Pile

Evidence is strongest when it is both scientifically reliable and directly applicable to the evaluated device. A useful working hierarchy begins with relevant data on the final finished device, including sterilization where applicable. Next comes well-justified evidence from an equivalent device or representative worst-case configuration. Chemical characterization and toxicological assessment can address constituent exposure questions. Published literature, supplier information, and clinical or post-market history can provide valuable support, but their relevance and limitations must be explicit.

This is not a rigid ranking. A robust chemistry and toxicology package may answer a question that an unrelated finished-device test cannot. Conversely, a general statement that a base polymer has a history of use does not resolve risks introduced by a new additive, coating, cleaning process, or sterilization cycle. Evaluate evidence by device match, contact route, exposure duration, formulation, manufacturing, sterilization, method quality, acceptance criteria, and access to underlying data.

Record unfavourable and inconclusive evidence as deliberately as favourable results. A failed study, unidentified chemical, literature signal, or complaint trend should not disappear from the narrative; it should trigger an investigation, risk-control decision, additional evidence, or a transparent explanation of why it does not change the conclusion. Reviewers need to see how uncertainty was managed, not merely the final answer.

Step 4: Make Every Endpoint a Documented Decision

For each biological effect relevant to the contact scenario, state the hazard being considered, the evidence relied upon, why that evidence applies, its limitations, and the conclusion or remaining gap. “Not applicable” and “passed previously” are not complete rationales. A decision that no new testing is needed requires a positive scientific argument that the available information controls the uncertainty without a new study.

The decision should be proportionate. New testing may be appropriate where a material or process is novel, existing data do not represent the final device, a high-consequence hazard remains uncertain, or a change affects exposure. Additional testing may be avoidable when the comparison is adequately documented and existing evidence directly addresses the hazard. Use the ISO 10993 biological endpoint selection guide to map contact and exposure to biological questions and evidence routes; FDA's endpoint tables explicitly describe a framework for evaluation rather than a test checklist.

Step 5: Connect Chemistry and Toxicology at the Right Time

ISO 10993-18:2020, including Amendment 1:2022, provides a stepwise framework for chemical characterization, including materials of construction, manufacturing-introduced substances, extractables, leachables, and relevant degradation products. ISO 10993-17:2023, including Amendment 1:2025, addresses toxicological risk assessment of device constituents using chemical characterization information when that assessment is needed.

Do not order extractables testing first and decide its purpose later. Define the clinical exposure scenario, device quantity, extraction rationale, analytical objectives, reporting approach, and expected toxicological use before the laboratory protocol is approved. The TRA then needs defensible constituent identity, amount, patient exposure assumptions, toxicological information, uncertainty treatment, and a conclusion connected back to the biological risk analysis. A practical ISO 10993-17 chemistry-to-BER walkthrough can help teams audit that handoff.

Step 6: Choose a Representative Test Article

If new testing is needed, explain why the selected article represents the marketed device. Consider formulation, processing, sterilization, geometry, surface area, thickness, colour, coating, joining materials, degradation state, and whether the proposed configuration is a meaningful worst case. FDA's official test-article documentation examples show the level of comparison needed when relying on a test article or previously marketed device.

Device-Specific Examples

• Hydrogel wound dressing: the base polymer is only one input. Evaluation may also need to address cross-linkers, preservatives, colorants, degradation, wound-fluid contact, wear duration, repeated replacement, and the finished sterilized product.
• Blood-contacting catheter: the fluid path, coating, adhesive joints, flushing solution, duration, flow conditions, and surface changes during use can influence chemistry, hemocompatibility, and test-article selection.
• Permanent coated implant: long-term local tissue response, systemic exposure to released constituents, coating integrity, wear or corrosion, degradation, sterilization, and worst-case geometry must form one connected argument.
• Reusable surgical instrument: initial-device evidence may not represent the device after the claimed number of cleaning, disinfection, and sterilization cycles. The evaluation should address residues and surface or material changes at an appropriate end-of-life condition.

Step 7: Translate the Strategy Into BEP and BER

The Biological Evaluation Plan should make the prospective logic auditable: scope, standards and guidance versions, contact classification, material and process information, biological hazards, endpoint decisions, evidence sources, gaps, test-article rationale, and planned work. Responsibilities and acceptance logic should be clear enough that testing, chemistry, and toxicology providers understand how their outputs will be used.

The Biological Evaluation Report closes the loop after evidence is available. It should evaluate—not merely list—the data, resolve deviations and limitations, state conclusions for each biological risk, align with the risk-management file, and identify any production or post-production information that could trigger reassessment.

Common Failure Modes

• Copying an endpoint table without explaining device-specific hazards and exposure.
• Describing only nominal raw materials while omitting additives, bonding, processing, packaging, or sterilization.
• Using old test reports without demonstrating comparability to the current finished device.
• Treating a supplier declaration or “medical grade” label as a complete biological-safety conclusion.
• Commissioning chemistry without a clinical exposure model or a plan for toxicological interpretation.
• Selecting a convenient test coupon without documenting representativeness or worst-case rationale.
• Letting the BEP, laboratory protocols, TRA, BER, and risk-management file use conflicting device versions or assumptions.

Plan for Re-evaluation

Biological evaluation is a lifecycle activity. Define triggers such as formulation or supplier changes, new manufacturing aids, site transfer, sterilization changes, packaging changes, altered contact duration, new complaints, toxicological information, or evidence of degradation. A concise change assessment should determine whether the existing evaluation remains applicable and what must be updated.