Can You Patent a Diagnostic Test in the UK in 2026?

Can you patent a diagnostic test under current UK and European patent rules? The answer is nuanced: methods of diagnosis practised on the human or animal body are excluded from patentability under Article 53(c) of the European Patent Convention (EPC) and mirrored provisions in the UK Patents Act 1977, yet a wide range of diagnostic inventions, in vitro assays, reagent compositions, antibody-based kits and analytical apparatus, remain fully patentable when claims are properly drafted. The April 2026 edition of the EPO Guidelines for Examination has refined how examiners assess the boundary between excluded in vivo diagnostic methods and allowable in vitro or ex vivo claims, creating both fresh opportunities and new pitfalls for applicants.

This guide breaks down the legal framework, the 2026 changes, practical claim‑drafting routes, costs, and a jurisdiction comparison so that biotech founders, in‑house counsel and R&D directors can make informed filing decisions.

Short Answer: Can You Patent a Diagnostic Test?

Yes, but the claim format matters decisively. Under Article 53(c) EPC and Section 4A of the UK Manual of Patent Practice, a method claim that recites every step of clinical diagnosis on a living patient or animal is excluded. However, the exclusion is narrow. If the inventive contribution lies in an in vitro or ex vivo analytical step, or if the claim is directed to a composition, reagent, kit or apparatus, it can be patented provided it meets the standard requirements of novelty, inventive step and sufficiency of disclosure. The EPO Guidelines 2026 edition reinforces this position while clarifying examiner practice on borderline cases.

• In vitro and ex vivo method claims, generally patentable when no step is practised on the body.
• Composition, reagent and antibody claims, patentable as products, regardless of ultimate diagnostic use.
• Method claims including an in vivo step, likely excluded unless the in vivo step is not the inventive contribution and can be separated from the claim.

Quick Legal Framework: UK and EPO Rules on Patenting Diagnostic Methods

Two overlapping legal regimes govern whether a diagnostic invention can be patented in the United Kingdom. Domestically, the Patents Act 1977 implements the UK’s obligations under the EPC. For European patent applications designating the UK (or, post-Brexit, the UK national phase of EP patents validated before 2021 and new UK national filings), the EPC itself and the EPO’s examination practice are determinative. In practice, the UK Intellectual Property Office (IPO) follows EPO case law closely, meaning that a claim strategy developed for EPO prosecution will usually succeed in the UK as well.

Article 53(c) EPC, Text and 2026 Interpretation

Article 53(c) EPC states that European patents shall not be granted in respect of “methods for treatment of the human or animal body by surgery or therapy and diagnostic methods practised on the human or animal body. ” The critical phrase is practised on the human or animal body. The EPO Boards of Appeal have consistently held that for a method to fall within this exclusion, the claim must include all of the following technical steps: (i) the examination phase (collecting data from the body), (ii) comparison of data with standard values, (iii) identification of a deviation, and (iv) attribution of that deviation to a particular clinical picture, the so-called “diagnosis for curative purposes.

” If any one of those steps is absent or if the examination phase does not take place on a living body, the exclusion does not apply. The April 2026 EPO Guidelines reinforce this multi-step test while adding worked examples that assist examiners in distinguishing borderline claims.

UK Manual of Patent Practice Section 4A, How UK Examiners Treat Diagnostics

Section 4A of the IPO’s Manual of Patent Practice tracks the EPC exclusion. It confirms that methods of diagnosis practised on the human or animal body are not patentable inventions under Sections 4A(1) and 4A(2) of the Patents Act 1977. Importantly, the Manual notes that the exclusion is limited: claims directed to apparatus, substances or compositions for use in diagnosis, and in vitro testing methods, are not caught. UK examiners are instructed to follow EPO Boards of Appeal reasoning, and Section 4A is regularly updated to incorporate new EPO decisions. For applicants, this alignment means that a single, well-structured claim set can generally serve both UK and EP filings.

What the EPO Guidelines (April 2026) Changed, Practical Implications

The April 2026 update to the EPO Guidelines for Examination is the most significant revision in several years for life-sciences applicants seeking to patent diagnostic inventions. While the underlying legal test under Article 53(c) EPC remains unchanged, the 2026 edition adds granularity to how examiners should assess whether a diagnostic claim is “practised on the body,” provides expanded worked examples for in vitro and ex vivo claim formats, and integrates updated guidance on antibody and biotech claim practice that had previously been scattered across multiple chapters.

Industry observers expect the practical effect to be threefold. First, examiners now have clearer internal direction to allow in vitro analytical method claims where no step requires interaction with a living body, even if the ultimate purpose of the analysis is diagnostic. Second, the guidelines clarify that a claim is not automatically excluded simply because the sample was originally obtained from a patient, the relevant question is whether the claimed method itself includes a step practised on the body. Third, the 2026 edition introduces refined language around antibody-based diagnostic kits, aligning biotech claim practice with recent Board of Appeal reasoning on product claims for diagnostic reagents.

For applicants, early indications suggest that the updated guidelines will make it easier to prosecute in vitro claims to grant, provided the claims are correctly drafted from the outset, while also giving opponents slightly clearer grounds to challenge claims that straddle the in vivo / in vitro boundary.

In Vitro / Ex Vivo vs In Vivo Distinction, Examples

The boundary between in vitro and in vivo is the single most important drafting variable when patenting diagnostic methods at the EPO. An in vitro claim that recites steps performed on a blood sample in a laboratory, measuring biomarker concentration, comparing to a reference range, and outputting a risk score, will generally survive the Article 53(c) objection. By contrast, a claim that includes an active step such as “administering a contrast agent to a patient and imaging the patient’s liver” introduces an in vivo element that engages the exclusion.

The 2026 Guidelines reinforce that claims directed to purely analytical methods performed on samples already removed from the body are outside the scope of the exclusion, even where the claim recites that the sample is, for example, “a human blood sample. ” This is a meaningful clarification: it resolves lingering examiner uncertainty about whether referencing the human origin of a sample converts an in vitro method into a method practised on the body.

Reagents, Antibodies and Composition Claims

Can an antibody be patented for diagnostic use? Yes. Product claims, compositions, reagent formulations, monoclonal or recombinant antibodies, labelled probes, are not methods and therefore fall entirely outside the diagnostic method exclusion. The April 2026 Guidelines confirm that product claims for diagnostic reagents are examined under the ordinary patentability requirements (novelty, inventive step, industrial applicability, sufficiency) without any Article 53(c) overlay. This means a novel antibody that binds a newly discovered biomarker can be claimed as a composition of matter, irrespective of its intended diagnostic application. Use claims of the type “use of antibody X for detecting biomarker Y in a sample” are similarly allowed, provided the claim does not include steps practised on the body.

Applicants should note that purpose-limited product claims (“Antibody X for use in diagnosing condition Z”) may require careful wording to avoid inadvertently importing method steps.

In Vitro vs In Vivo: Drafting Routes and Claim Formats for Patenting Diagnostic Methods

Effective claim drafting is the most practical tool available to secure patent protection for diagnostic inventions at both the EPO and the UK IPO. Below are the principal claim formats, with illustrative templates and prosecution notes. These examples are provided for educational purposes and should be adapted to the specific invention with professional guidance.

Safe Route 1, Composition, Reagent and Antibody Claims

Product claims are the safest route because Article 53(c) EPC applies only to methods. A reagent or antibody claim protects the physical product regardless of how it is used downstream.

Example claim template A, composition claim: “A composition comprising antibody X that specifically binds biomarker Y, wherein antibody X is conjugated to a detectable label selected from [fluorescent dye, enzyme, nanoparticle].”

Example claim template B, kit claim: “A diagnostic kit comprising: (a) a lateral-flow test strip coated with capture antibody X; (b) a conjugate pad impregnated with labelled detection antibody Z; and (c) a sample application zone configured to receive a biological fluid sample.”

Prosecution notes: product claims avoid the Article 53(c) objection entirely. The key prosecution risk is novelty and inventive step: the applicant must demonstrate that the specific antibody, labelling or kit configuration is new and non-obvious. Supporting data showing improved sensitivity, specificity or stability strengthens the case during examination and in any future opposition.

Safe Route 2, Apparatus and Kit Claims

Apparatus claims directed to a physical device, a biosensor, a microfluidic chip, a point-of-care reader, are likewise outside the method exclusion. These claims protect the hardware, software architecture and functional configuration of the diagnostic device.

Example claim template C, apparatus claim: “An apparatus for analysing a biological sample for the presence of analyte Y, the apparatus comprising: a sample chamber; a sensor element functionalised with capture molecule X; a processor configured to compare a detected signal with a stored reference threshold; and a display configured to output a risk classification.”

Prosecution notes: apparatus claims can carry broad scope and are particularly valuable for point-of-care and digital diagnostics companies. The inventive step often lies in the sensor design or signal processing algorithm, and supporting experimental data demonstrating improved performance should be included in the application as filed.

Safe Route 3, In Vitro Method Claims and Diagnostic Carve-outs

Where the invention lies in the analytical method itself, an in vitro method claim can be drafted to stay outside the exclusion, provided no step is practised on the body.

Example claim template D, in vitro analytical method: “An in vitro method for determining the presence of biomarker Y in a biological sample, the method comprising: (i) contacting the sample with antibody X under conditions permitting binding; (ii) detecting a signal indicative of binding between antibody X and biomarker Y; and (iii) correlating the detected signal with a reference dataset to generate a risk score.”

Example claim template E, use claim: “Use of antibody X for detecting biomarker Y in a biological sample obtained from a subject suspected of having condition Z.”

Prosecution notes: the critical discipline is to ensure that no step in the claim requires anything to happen to the patient. Steps such as “obtaining a sample from a patient” are best omitted or replaced with “provided with a biological sample.” The 2026 Guidelines indicate that examiners should not object to a claim merely because the sample is of human origin, but phrasing that implies active sample collection from a living body may still trigger an objection. Including fallback claims, for example, a dependent claim narrowing to a specific analyte or sample type, provides prosecution flexibility if the broadest claim encounters resistance.

EPO vs UK vs US: Comparison Table and Practical Takeaways

Diagnostic inventors often file in multiple jurisdictions. The table below summarises the key exclusion rules and practical workarounds in the three most commercially relevant patent systems. Understanding these differences is essential for protecting intellectual property across borders.

The EPO Guidelines 2026 make the European system somewhat more applicant-friendly for in vitro claims compared with the US approach, where the Mayo two-step test continues to create uncertainty even for clearly in vitro methods. Early indications suggest that applicants pursuing global filing strategies should draft the broadest in vitro claims for the EPO and UK, while preparing separate US-specific claims that emphasise unconventional method steps and specific reagent improvements.

In the UK specifically, the alignment with EPO practice means that claim sets optimised for EP prosecution rarely need significant amendment for UK national filings. This is a practical advantage for budget-conscious SMEs and startups aiming to secure patent protection in both jurisdictions efficiently. Further context on the international intellectual property landscape is available in our separate guide.

Evidence, Support Data and Sufficiency: What Examiners and Opponents Will Ask

Securing a granted patent for a diagnostic test is only the first challenge. The claims must also withstand opposition and, potentially, court proceedings. Whether the application is being examined at the EPO or the UK IPO, examiners will scrutinise two areas: (a) whether the claimed technical effect is supported by the data in the application, and (b) whether the disclosure is sufficient to enable a person skilled in the art to reproduce the invention.

For diagnostic inventions, the “technical effect” typically relates to improved sensitivity, specificity, speed, reproducibility or cost-effectiveness compared with the prior art. Applicants should include comparative experimental data, even preliminary data, in the application as filed. Post-filing data can support inventive step arguments but cannot cure a fundamental insufficiency in the original disclosure.

Examples of Minimal Supporting Data

At a minimum, a diagnostic patent application should include data demonstrating that the assay works as claimed. This might take the form of binding curves for an antibody-antigen interaction, receiver operating characteristic (ROC) analysis showing clinical sensitivity and specificity, or dose-response data for a biosensor. Even a small dataset, ten patient samples and ten controls, can satisfy sufficiency if it is properly described and statistically analysed. Including data from more than one sample type (for example, serum and plasma) strengthens the case that the invention is reproducible across conditions.

Opposition and Appeal Vulnerabilities, How to Mitigate

The most common opposition grounds for diagnostic patents are lack of inventive step (the assay is an obvious modification of known methods), insufficiency (the disclosure does not enable the skilled person to achieve the claimed result across the full scope), and added matter (amendments introduced during prosecution go beyond the original filing). To mitigate these risks, applicants should file broad independent claims supported by a cascade of narrower dependent claims, include extensive worked examples in the description, and avoid amending claims during prosecution in ways that introduce features not explicitly disclosed. For strategies on defending granted patents and handling intellectual property enforcement challenges, specialist advice is recommended.

Commercial Considerations: Costs, Timelines and Filing Strategy

Understanding how much it costs to get a patent in the UK, and at the EPO, is critical for biotech SMEs and startups allocating limited budgets. The table below provides indicative cost ranges for professional fees and official fees combined. Actual costs vary depending on the complexity of the invention, the number of claims and the jurisdictions designated.

Note: all figures are indicative and will vary based on attorney rates, invention complexity and prosecution history. They should not be treated as a quotation.

A recommended filing strategy for diagnostics is to file a UK priority application first (lower cost, fast search report), followed by a PCT application within the 12-month priority period to preserve options internationally. The PCT search report then informs whether to enter the EP regional phase and/or individual national phases. This approach balances cost control with maximum geographic flexibility and is the strategy most commonly advised for life-sciences startups entering the market.

When to Pursue a Patent vs Trade Secret vs Regulatory Exclusivity

Not every diagnostic innovation is best protected by a patent. If the inventive element cannot be reverse-engineered from the commercial product, for example, a proprietary machine-learning model trained on clinical data, trade secret protection may offer indefinite protection without the cost or disclosure requirements of a patent filing. Conversely, if competitors could independently develop the same assay, a patent provides the strongest enforceable right.

Regulatory data exclusivity, such as the data protection periods available under the EU In Vitro Diagnostic Regulation (IVDR) or the UK’s post-Brexit equivalent, can complement patent protection by preventing competitors from relying on the originator’s clinical data for a defined period. The optimal strategy often combines patent protection for the core assay or reagent with trade secret protection for manufacturing know-how and regulatory exclusivity for the clinical dataset. Each case should be assessed individually based on the technology, market timing and competitive landscape.

Practical Checklist for Drafting and Filing a Diagnostics Patent

• Include multiple claim types. File independent claims in at least three formats: composition/reagent, kit/apparatus, and in vitro method.
• Avoid in vivo language. Do not recite steps performed on the body; use “provided with a biological sample” rather than “obtaining a sample from a patient.”
• Include experimental data. At minimum, provide binding data, sensitivity/specificity metrics, and at least one worked example with real samples.
• Draft fallback claims. Include a cascade of dependent claims narrowing to specific biomarkers, sample types, antibody formats and detection platforms.
• Prioritise jurisdictions strategically. File UK priority, then PCT; enter EP and US national phases based on commercial plans and search report results.
• Conduct freedom-to-operate analysis. Before filing, search for third-party rights in core biomarkers, antibodies and detection technologies.
• Prepare for opposition. Assume the patent will be opposed; structure the description and claims to withstand inventive step and sufficiency challenges.

Conclusion

The question of whether you can you patent a diagnostic test in the UK does not have a binary answer, it depends on how the claims are drafted, which steps are recited, and whether the inventive contribution is embodied in a product, an in vitro method, or an in vivo clinical procedure. The April 2026 EPO Guidelines have brought welcome clarity to the in vitro versus in vivo boundary and to antibody and reagent claim practice, making it easier for well-advised applicants to secure meaningful patent protection for diagnostic innovations. The UK IPO’s alignment with EPO case law means that a carefully constructed European claim strategy will generally succeed domestically as well.

For biotech startups, clinical laboratories and diagnostic device companies, the practical takeaway is clear: invest in professional claim drafting from the outset, support your application with robust experimental data, and plan for opposition. Doing so maximises the chance of obtaining a granted patent that withstands challenge and delivers genuine commercial value.

Sources

1. European Patent Convention, Article 53
2. EPO Guidelines for Examination (April 2026 edition)
3. GOV.UK, Manual of Patent Practice, Section 4A
4. UK Patents Act 1977
5. US Supreme Court, Mayo Collaborative Services v. Prometheus Laboratories, Inc., 566 U.S. 66 (2012)