Risk-based biocompatibility testing

What Is Risk-Based Biocompatibility Testing — and Why Does It Matter?

Furthermore,

Risk-based biocompatibility testing is a structured, science-driven approach that evaluates medical device materials by matching the depth of biological safety testing to the actual patient risk the device presents. Moreover, rather than running every possible biological assay, this framework — anchored in Materials Metric’s analytical expertise — prioritizes chemical characterization, exposure modeling, and toxicological risk assessment to determine which tests are truly necessary. Consequently, manufacturers reduce costs and timelines without compromising patient safety.

In addition,

Regulators worldwide now expect this approach. However, the ISO 10993 series, particularly the 2018 revision of Part 1, fundamentally shifted the industry away from default animal testing toward a chemical characterization-first methodology. Furthermore, the FDA’s guidance on use of ISO 10993-18 Chemical Characterization reinforces that a well-executed chemical analysis can eliminate or minimize the need for costly in vivo studies. As a result, chemical data now drives biological evaluation decisions at every stage.

Therefore,

For engineers, quality managers, and regulatory affairs professionals, understanding this framework is essential. In addition, procurement teams selecting raw materials must grasp how material choices upstream directly affect the biocompatibility testing burden downstream. This first half of our guide covers the foundational concepts, the regulatory framework, and the chemical characterization methods that underpin every successful risk-based program.

Key Takeaways

Risk-based biocompatibility testing tailors biological safety testing to actual patient exposure risk, reducing unnecessary animal studies.

ISO 10993-1 (2018) and ISO 10993-18 mandate chemical characterization as the foundation of every biological evaluation.

Analytical thresholds — tolerable intake (TI), tolerable contact level (TCL), and the analytical evaluation threshold (AET) — guide which chemicals require further toxicological review.

Chemical characterization methods such as GC-MS Analysis, HPLC Analysis, and XRF Analysis form the analytical backbone of the process.

A Biological Evaluation Plan (BEP) and Biological Evaluation Report (BER) document the entire risk justification for regulators.

Expert support — from Scientific & Technical Consulting to accredited laboratory testing — accelerates regulatory submission timelines.

Risk-Based Biocompatibility Testing: A regulatory and scientific methodology — defined by the ISO 10993 standard series — that determines the biological safety of medical device materials by first characterizing their chemical composition and patient exposure, then applying toxicological risk principles to decide which, if any, biological tests are required, rather than applying a fixed battery of assays to every device.

Key fact: ISO 10993-1 (2018) formally established chemical characterization and risk assessment as the primary tools for biological evaluation — making biological testing the exception rather than the default starting point for medical device safety programs.

What Is the ISO 10993 Framework for Risk-Based Biocompatibility Testing?

Consequently,

The ISO 10993 series provides the global regulatory foundation for medical device biocompatibility. Specifically, Part 1 of the standard defines the overall biological evaluation process and sets out a risk management approach aligned with ISO 14971. Therefore, every biological evaluation must begin with a structured plan — the Biological Evaluation Plan, or BEP — that documents the rationale for each decision made about testing.

Notably, the 2018 revision of ISO 10993-1 made chemical characterization a required first step rather than an optional one. Furthermore, it clarified that existing data, material history, and chemical analysis can justify waiving certain biological endpoints entirely. Consequently, manufacturers with well-documented supply chains and robust material data packages gain a significant regulatory advantage.

How Device Categorization Shapes the Risk Profile

As a result,

ISO 10993-1 classifies devices by two key variables: nature of body contact and duration of contact. Specifically, surface-contacting devices, externally communicating devices, and implanted devices each carry different risk levels. Similarly, contact duration — limited (under 24 hours), prolonged (up to 30 days), and permanent (over 30 days) — directly determines which biological endpoints regulators expect manufacturers to address.

Notably,

Consider a short-term skin-contact electrode versus a permanent cardiac implant. The electrode presents minimal systemic exposure; therefore, a focused chemical characterization may be sufficient. By contrast, the cardiac implant demands a comprehensive evaluation covering cytotoxicity, sensitization, genotoxicity, implantation, and chronic toxicity, among other endpoints. Matching the evaluation depth to actual risk is precisely what the risk-based approach achieves.

The Biological Evaluation Plan and Report

Importantly,

Every risk-based biocompatibility testing program must produce a Biological Evaluation Plan before any testing begins. Meanwhile, the BEP defines the device description, materials of construction, intended patient contact, regulatory requirements, and the rationale for selecting or waiving each biological endpoint. Moreover, it establishes the analytical strategy — identifying which chemical characterization methods will be used to generate the data needed for toxicological risk assessment.

By contrast,

Once testing and characterization are complete, the Biological Evaluation Report captures all findings, risk conclusions, and any residual risks. For example, regulators — including the FDA and European Notified Bodies — review the BER as a core submission document. Therefore, a well-structured, scientifically defensible BER is one of the most critical assets a manufacturer can produce. For teams that need expert support in drafting these documents, Scientific & Technical Consulting services can significantly reduce revision cycles.

Aligning with FDA Expectations

In particular,

The FDA recognizes ISO 10993-1 as a consensus standard and has published specific guidance on how it interprets the risk-based approach for submissions. For instance, the agency expects manufacturers to explain why each biological endpoint was addressed — or why it was not — based on chemical and clinical evidence. Furthermore, the FDA has increasingly scrutinized submissions that simply list biological test results without providing the underlying risk justification.

Similarly,

Our detailed FDA chemical characterization review guide explains the specific documentation expectations manufacturers must meet. In addition, understanding the FDA’s position on extractables and leachables testing helps teams anticipate reviewer questions before submission.

Why Chemical Characterization Is the Foundation of Risk-Based Biocompatibility Testing

Chemical characterization identifies and quantifies all chemical substances that may migrate from a medical device into the patient. This process produces the data needed to assess whether each substance poses an unacceptable toxicological risk. Consequently, it replaces or reduces the need for biological assays by demonstrating — analytically — that chemical exposures fall below established safety thresholds.

The ISO 10993-18 standard governs chemical characterization of medical device materials. It establishes a tiered analytical workflow that moves from material identification through extraction and analytical testing to toxicological risk assessment. Moreover, it defines the analytical evaluation threshold (AET) — the minimum mass of a substance that the analytical method must reliably detect and quantify. Substances detected below the AET do not require further toxicological evaluation.

Extractables and Leachables: What Is the Difference?

Extractables are chemical substances that migrate from a material under aggressive laboratory extraction conditions — typically using solvents, elevated temperatures, or extremes of pH. These represent the worst-case chemical inventory of a material. Leachables, by contrast, are the subset of extractables that actually migrate under normal or simulated clinical use conditions. Therefore, leachables represent the true patient exposure scenario.

A thorough extractables study establishes the universe of chemicals potentially present in a device. Subsequently, leachables testing — conducted under realistic use conditions — confirms actual patient exposure levels. For many devices, the combined extractables and leachables dataset is sufficient to perform a full toxicological risk assessment without any additional biological testing. Our Biocompatibility & Toxicity Testing team manages both phases of this analytical workflow.

Key Analytical Methods Used in Chemical Characterization

Selecting the right analytical methods is critical to generating a complete and defensible chemical inventory. Each method detects a different class of chemical compounds; therefore, a multi-technique approach is standard practice. The table below summarizes the most common methods and their primary applications in biocompatibility-related chemical characterization.

Analytical Method	Primary Application	Typical Targets
GC-MS Analysis	Volatile and semi-volatile organics	Residual solvents, plasticizers, antioxidants
HPLC Analysis	Non-volatile organics	Polymer additives, colorants, UV stabilizers
XRF Analysis	Elemental screening	Heavy metals, elemental impurities (rapid screen)
XPS Analysis	Surface elemental composition	Surface coatings, oxidation states, contamination
FTIR Analysis	Polymer and organic identification	Material identity, degradation products
NMR Spectroscopy	Structural identification of unknowns	Leachable identification, unknown compound structure

In addition to these primary methods, elemental analysis via ICP-MS is widely used to quantify trace metals against the limits defined in USP General Chapter <232> Elemental Impurities. Furthermore, SEM Analysis supports particle characterization and surface morphology assessment when device geometry or particulate release is a concern.

Setting the Analytical Evaluation Threshold

The AET is a critical concept in risk-based biocompatibility testing. It defines the lowest concentration a laboratory method must reliably detect. Substances present below the AET pose negligible risk and require no further toxicological evaluation. Therefore, setting an appropriate AET — based on the device’s patient contact category and exposure duration — directly determines the scope of analytical work required.

Calculating the AET involves dividing the toxicological threshold of concern (TTC) by the maximum daily patient exposure, then applying a conservative safety margin. Our detailed guide to the analytical evaluation threshold walks through this calculation with worked examples. In addition, understanding AET calculation helps teams select sufficiently sensitive analytical instruments and validate methods appropriately, as described under Method Development & Validation.

Quick note: Selecting analytical methods with sensitivity well below the AET — rather than exactly at it — provides a critical safety margin. Moreover, it protects against method variability and matrix interferences that could otherwise cause substances to be missed in the chemical inventory.

How Toxicological Risk Assessment Drives the Testing Decision in Risk-Based Biocompatibility Testing

Once chemical characterization identifies and quantifies the extractables and leachables present in a device, toxicological risk assessment determines whether each substance poses an unacceptable risk to patients. Specifically, toxicologists compare the patient’s estimated daily intake of each substance against established safety thresholds. When the patient exposure falls below those thresholds, no further biological testing is required for that chemical endpoint.

This process relies on internationally recognized toxicological databases and published literature. Sources such as PubMed Central – Trace Metals Review provide toxicity data, no-observed-adverse-effect levels (NOAELs), and benchmark dose values that toxicologists use to establish tolerable intake levels. Furthermore, Nature Reviews Methods Primers publishes methodological guidance that supports rigorous analytical and toxicological method selection.

Threshold of Toxicological Concern and Tolerable Intake

Two key toxicological thresholds underpin risk-based biocompatibility testing decisions. The threshold of toxicological concern (TTC) represents a universal exposure level below which any chemical — regardless of structure — poses negligible risk. Meanwhile, the tolerable intake (TI) is a substance-specific threshold derived from the NOAEL divided by appropriate safety factors.

When patient exposure to a leachable is below both the TTC and the substance-specific TI, the toxicological risk assessment can conclude that no biological testing is required for that substance. However, when exposure exceeds these thresholds, additional data — either from literature or from targeted biological assays — becomes necessary. Therefore, the quality of the chemical characterization data directly gates the toxicological conclusion. Our toxicological risk assessment guide covers the full calculation workflow in detail.

Cytotoxicity, Sensitization, and Genotoxicity: When Biological Testing Remains Necessary

Some biological endpoints cannot be fully addressed through chemical characterization alone. Cytotoxicity testing, for example, assesses the direct toxic effect of a material or extract on living cells and remains a standard first-tier test for most device categories. Sensitization testing evaluates whether a material or its extractables can trigger an immune-mediated allergic response. Moreover, genotoxicity studies assess the potential of chemicals to damage DNA — a concern that chemical databases may not fully resolve for novel or complex leachable mixtures.

For these endpoints, Biocompatibility & Toxicity Testing services provide the structured in vitro and in vivo studies required by ISO 10993. Furthermore, integrating biological testing data with chemical characterization data — rather than treating them as separate programs — produces a more coherent and defensible BER. The ScienceDirect – Analytical Methods journal documents many of the validated approaches used to integrate chemical and biological datasets in modern biocompatibility programs.

Risk Benefit Analysis and Residual Risk

Not every risk identified through toxicological assessment will be zero. In some cases, a leachable may exceed a threshold for a device that provides life-saving clinical benefit. In those situations, risk-benefit analysis — a core component of ISO 14971 — determines whether the clinical benefit justifies the residual chemical risk. Consequently, the BER must clearly document this analysis and its supporting rationale.

Residual risk conclusions require manufacturer sign-off from qualified toxicologists and clinical specialists. Furthermore, post-market surveillance data can provide real-world evidence to support ongoing risk management decisions. For teams building this capability internally, Scientific & Technical Consulting provides expert toxicological and regulatory review support tailored to device-specific risk profiles. Our Chemical & Analytical Testing services generate the underlying data that makes those risk conclusions defensible.

Advanced Analytical Techniques Supporting Risk-Based Biocompatibility Testing

Chemical characterization demands highly sensitive, orthogonal analytical methods. Selecting the right technique depends on the chemical class of interest, the required detection limit, and the device matrix. Furthermore, combining multiple methods ensures complete coverage of the chemical inventory — a requirement under ISO 10993-18 for robust risk-based programs.

ICP-MS and ICP-OES for Elemental Analysis

Inductively coupled plasma mass spectrometry (ICP-MS) is the gold standard for trace elemental quantification in biocompatibility programs. It detects metals and metalloids at parts-per-trillion concentrations — well below the AET for most device categories. Consequently, ICP-MS satisfies the stringent detection requirements of USP Elemental Impurities limits and ISO 10993-18 elemental characterization workflows.

ICP-OES (optical emission spectrometry) offers a complementary approach. It handles higher-concentration samples and a broader elemental range efficiently. Moreover, ICP-OES serves well as a screening tool before ICP-MS confirms trace-level findings. Together, these two techniques form a complete elemental characterization solution within our Chemical & Elemental Characterization service portfolio.

AAS, ICP-OES, and Method Selection Criteria

Atomic absorption spectrometry (AAS) remains a reliable, cost-effective option for single-element quantification. For example, graphite furnace AAS (GFAAS) achieves sub-ppb detection for elements like lead, arsenic, and cadmium — all critical elemental impurities in medical device materials. However, AAS analyzes one element per run, making it slower than ICP-based techniques for multi-element panels.

The table below compares key elemental techniques by detection capability, throughput, and typical application in risk-based biocompatibility testing programs.

Technique	Detection Range	Throughput	Best Application
ICP-MS	Parts per trillion (ppt)	High — multi-element	Trace elemental impurities, AET compliance
ICP-OES	Parts per billion (ppb)	High — multi-element	Major and minor elemental profiling
GFAAS	Sub-ppb	Low — single element	Targeted heavy metal confirmation
XRF Analysis	Parts per million (ppm)	Very high — rapid screen	Non-destructive elemental screening

Chromatographic and Spectroscopic Method Combinations

Organic leachables require a different analytical strategy from elemental impurities. GC-MS Analysis remains the primary workhorse for volatile and semi-volatile organics — capturing plasticizers, antioxidants, and residual processing solvents. Meanwhile, HPLC Analysis targets thermally labile, non-volatile compounds that GC-MS cannot reliably detect.

For structural identification of unknown leachables, NMR Spectroscopy and Raman Spectroscopy provide definitive molecular structure data. Additionally, FTIR Analysis confirms polymer identity and detects functional group changes indicative of degradation. Layering these orthogonal methods produces the comprehensive chemical inventory that regulators expect under a rigorous risk-based biocompatibility testing program. Our Method Development & Validation team ensures each method achieves the sensitivity and specificity the AET calculation requires.

Industry-Specific Applications of Risk-Based Biocompatibility Testing

Risk-based biocompatibility testing applies across multiple regulated industries. Each sector brings unique materials, patient populations, and regulatory frameworks. However, the underlying scientific logic — characterize first, test only what the risk profile demands — remains consistent across all applications.

Medical Devices: Implants, Drug Delivery, and Combination Products

Medical device manufacturers represent the core audience for ISO 10993-based risk-based programs. Implantable devices — orthopedic implants, cardiovascular stents, neural electrodes — demand the most comprehensive biological evaluations. Notably, permanent implants must address chronic systemic toxicity, carcinogenicity, and reproductive toxicity endpoints in addition to the standard cytotoxicity and sensitization tests.

Drug delivery devices and combination products introduce additional complexity. Leachables from a drug delivery container or prefilled syringe can interact directly with the drug product — potentially affecting safety, efficacy, or stability. Therefore, these products require coordinated chemical characterization under both ISO 10993-18 and pharmaceutical extractables and leachables (E&L) guidance. Our Biocompatibility & Toxicity Testing services support both regulatory frameworks within a single integrated program.

Pharmaceutical Packaging and Container Closure Systems

Container closure systems for parenteral drug products face strict E&L requirements from both the FDA and USP. Specifically, primary packaging materials — stoppers, vials, syringes, bags — must demonstrate that leachables remain below safety thresholds for the intended drug route of administration. The risk-based approach applies equally here: chemical characterization drives the testing strategy, and toxicological thresholds gate which leachables require further study.

Critically, the USP Elemental Impurities chapters establish permitted daily exposure limits for elemental impurities in drug products. Furthermore, our Chemical Purity & Contaminant Screening service provides the targeted screening studies pharmaceutical teams need to meet these limits efficiently.

Aerospace, Industrial, and Environmental Applications

Risk-based chemical characterization extends well beyond medical and pharmaceutical applications. Aerospace manufacturers, for instance, must characterize composite materials and specialty coatings to ensure worker safety and environmental compliance. Similarly, environmental regulators apply risk-based frameworks to assess chemical exposure from contaminated soil, water, and industrial emissions.

In each case, the core workflow mirrors the medical device approach: identify chemicals present, quantify exposure, compare against toxicological thresholds, and conclude on risk acceptability. Our Chemical & Analytical Testing services support these multi-sector programs with the same rigorous analytical standards applied in regulated medical and pharmaceutical programs. Furthermore, the ScienceDirect analytical chemistry literature documents validated methods applicable across all these industries.

Quality Assurance and Best Practices for Risk-Based Biocompatibility Testing Programs

A technically sound risk-based biocompatibility testing program must also meet rigorous quality standards. Analytical data used in regulatory submissions must originate from accredited, well-controlled laboratories operating under appropriate quality management systems. Consequently, quality assurance is not a separate activity — it is embedded in every stage of the program.

Laboratory Accreditation and Data Integrity

ISO/IEC 17025 accreditation is the benchmark for analytical testing laboratory competence. Accredited laboratories demonstrate documented proficiency in the specific test methods they perform, traceability to national measurement standards, and robust internal quality controls. Therefore, selecting an accredited laboratory for chemical characterization directly strengthens the regulatory defensibility of the resulting data.

Data integrity — ensuring that raw data is accurate, complete, and traceable — is equally critical. Regulatory agencies, particularly the FDA, have increased scrutiny of data integrity practices in laboratory submissions. In addition, all instrument calibrations, method validations, and analyst qualifications must be fully documented and retrievable for review during regulatory inspections.

Method Validation and Fit-for-Purpose Testing

Every analytical method used in a risk-based biocompatibility testing program must be validated for its intended purpose. Validation parameters include specificity, linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy, and precision. Moreover, the LOQ must fall below the AET to ensure the method can reliably detect all substances that require toxicological evaluation.

Fit-for-purpose validation acknowledges that not every study requires full pharmaceutical-grade method validation. However, even screening studies require documented evidence of method suitability. Our Method Development & Validation service provides appropriately scoped validation packages — from full ICH Q2(R1) validation to fit-for-purpose qualification — tailored to the submission requirements of each regulatory pathway.

Building a Robust Biological Evaluation Report

The BER is the central deliverable of any risk-based biocompatibility testing program. Regulators expect it to present a clear, logical narrative — not a collection of disconnected test reports. Specifically, the BER must connect the device’s materials, the chemical characterization findings, the toxicological risk conclusions, and the biological testing data into a coherent safety argument.

Quick note: A common BER deficiency is presenting biological test results without explaining why those specific endpoints were selected and how chemical data supported — or could not support — the risk conclusion. Reviewers expect the risk logic to be explicit, not implied.

Best-practice BERs also include a change control section documenting any material or process changes since the last evaluation. Furthermore, they reference applicable standards, guidance documents, and toxicological databases used in the assessment. For teams building their first BER or updating an existing one, Scientific & Technical Consulting provides structured review and gap analysis against current regulatory expectations. Additionally, our companion article on ISO 10993-18 compliance provides further detail on the chemical characterization documentation requirements reviewers examine most closely.

Change Control and Lifecycle Management

Risk-based biocompatibility testing is not a one-time exercise. Material changes, supplier changes, manufacturing process modifications, and sterilization method updates can all alter the chemical profile of a device. Therefore, manufacturers must maintain an active change control system that triggers biocompatibility re-evaluation whenever a potentially significant change occurs.

ISO 10993-1 requires manufacturers to define criteria for what constitutes a significant change for biocompatibility purposes. Moreover, post-market surveillance data — including adverse event reports and literature monitoring — must feed back into the biological evaluation on an ongoing basis. Our Chemical & Analytical Testing team supports lifecycle re-evaluation programs, including targeted re-characterization studies after material or process changes.

Frequently Asked Questions About Risk-Based Biocompatibility Testing

What is the difference between a risk-based approach and a test-based approach to biocompatibility?

A test-based approach applies a fixed battery of biological assays to every device, regardless of actual patient risk. By contrast, a risk-based approach starts with chemical characterization and toxicological assessment to determine which — if any — biological tests are truly necessary. Consequently, the risk-based approach is more scientifically rigorous, more cost-efficient, and better aligned with current ISO 10993-1 and FDA expectations.

Does risk-based biocompatibility testing eliminate the need for all animal testing?

Not always — but it significantly reduces it. When chemical characterization demonstrates that all leachables fall below established safety thresholds, biological testing can often be waived entirely. However, endpoints such as genotoxicity and implantation may still require in vitro or in vivo studies when chemical data cannot fully resolve the risk. The goal is to use biological testing only where it adds necessary risk information, not as a default starting point.

Which ISO 10993 parts are most relevant to risk-based biocompatibility testing?

Several parts of the ISO 10993 series are directly relevant. ISO 10993-1 defines the overall biological evaluation framework and risk management approach. ISO 10993-18 governs chemical characterization of medical device materials. Additionally, ISO 10993-17 covers toxicological risk assessment methods, while ISO 10993-12 defines material preparation and reference materials for biological testing. Together, these standards provide the complete regulatory basis for a risk-based program.

How long does a risk-based biocompatibility testing program typically take?

Timeline varies significantly depending on device complexity, material novelty, and the scope of chemical characterization required. A focused program for a simple, low-contact device using well-characterized materials may complete chemical characterization and toxicological risk assessment within six to ten weeks. By contrast, a comprehensive evaluation for a permanent implant using novel materials — including biological testing — may require six months or more. Early planning and a well-structured BEP reduce delays substantially.

Can previously generated chemical characterization data support a new device’s biocompatibility evaluation?

Yes — with appropriate justification. If a new device uses the same materials, the same suppliers, and the same manufacturing processes as a previously characterized device, existing chemical data can be leveraged. However, manufacturers must document that the new device’s patient contact type, duration, and exposure route are comparable to the original. Furthermore, any material or process changes since the original characterization must be assessed for potential impact on the chemical profile before relying on legacy data.

What role does the analytical evaluation threshold play in reducing testing burden?

The AET is one of the most powerful tools in risk-based biocompatibility testing. It defines the minimum concentration a laboratory method must detect reliably. Substances present below the AET carry negligible patient risk and require no further toxicological evaluation. Consequently, a well-set AET — combined with sufficiently sensitive analytical methods — can significantly narrow the list of leachables requiring full toxicological assessment, reducing both time and cost. Our detailed guide to the analytical evaluation threshold explains the calculation process and its regulatory basis in full.

Conclusion

Risk-based biocompatibility testing represents the modern standard for medical device safety evaluation. By anchoring every biological evaluation in rigorous chemical characterization and science-based toxicological risk assessment, manufacturers meet regulatory expectations while avoiding unnecessary testing. Furthermore, this approach produces stronger, more defensible documentation — exactly what FDA reviewers and Notified Bodies expect to see in today’s submissions.

The analytical foundation matters enormously. Selecting appropriately sensitive methods, validating them rigorously, and interpreting chemical data through a sound toxicological lens are the skills that separate compliant programs from deficient ones. Moreover, managing biocompatibility as a lifecycle activity — not a pre-market checkbox — ensures that devices remain safe as materials, suppliers, and processes evolve over time.

At Materials Metric, our team combines accredited analytical laboratory capabilities with deep regulatory expertise across the full ISO 10993 framework. From initial material screening and extractables studies through full toxicological risk assessment and BER preparation, we support every phase of the risk-based biocompatibility testing process. Additionally, our Wet Chemistry & Classical Analytical Methods capabilities complement advanced instrumental techniques to deliver complete chemical inventories for even the most complex device materials.

If your team is preparing a new biocompatibility program, updating an existing BER, or navigating a material change assessment, our experts are ready to help. Contact Materials Metric today to discuss your specific device, materials, and regulatory timeline — and let us help you build a risk-based program that satisfies regulators and protects patients.