The global market for in vitro diagnostics is forecast to achieve a revenue of almost US$100 billion in 2024 (Statista), with the US and Europe playing a major role in this sector. Both the EPO and USPTO have provisions for excluding diagnostic methods from patentability, but the scope of these exclusions differs considerably. In the US, diagnostic methods are often deemed ineligible for patent protection. An applicant may be able to escape this exclusion by demonstrating an “inventive concept” in the practical application of a natural phenomenon, such as the use of unconventional techniques. In contrast, in Europe, there is a much narrower prohibition on the patenting of diagnostic methods that are practised on the human or animal body. A number of decisions from the EPO Boards of Appeal have outlined the limits of this exclusion, and there are many opportunities for applicants to claim aspects of diagnostic methods in Europe which are not available in the US. We review some of the key decisions at the EPO and discuss the practical impact for applicants.

Article 53(c) of the European Patent Convention excludes from patentability “diagnostic methods practised on the human or animal body”. In decision G1/04, the Enlarged Board of Appeal defined what is understood by a diagnostic method according to Article 53(c) EPC. As summarised in the EPO’s Guidelines for Examination, G1/04 established that a diagnostic method is excluded from patentability only if it includes all of the following phases:

1. the examination phase, involving the collection of data;
2. the comparison of these data with standard values;
3. the finding of any significant deviation, i.e. a symptom, during the comparison; and
4. the attribution of the deviation to a particular clinical picture, i.e. the deductive medical or veterinary decision phase (diagnosis for curative purposes stricto sensu).

There is also a requirement that phases (1) to (3) must all be practised on the human or animal body. This criterion has been interpreted quite broadly, such that most interactions with the human or animal body can in principle fulfil this requirement.

Simply omitting one or more of steps (1) to (4) from a diagnostic method claim is not necessarily a route to patentability. If it is clear that these steps will still be carried out as part of the claimed method, then the omitted steps might be deemed to be implicitly present in the claim, and so the exclusion may still bite. For instance, T1016/10 considered a claim concerning ocular measurements for diagnosing an amyloidogenic disorder. The claim was found to require step (1) implicitly, even though the proprietor had removed the claim features explicitly requiring examination of the ocular lens. The Enlarged Board in G1/04 also highlighted that excluding a step from the claim may lead to non-compliance with other provisions. For example, removing one of steps (1) to (4) would not be allowable if it was clear from the application as a whole that the step taken out was essential for performing the claimed method. This is because such a claim would then impermissibly lack the essential technical features necessary to carry out the invention.

Claims directed to methods in which one of steps (1) to (3) occurs in vitro or ex vivo should not fall under the exclusion. For example, in T666/05, patent eligibility was acknowledged for a method of diagnosing the predisposition for cancer by detecting a mutation in the BRCA1 gene in a tissue sample. The Board remarked that all of the technical steps of this method were performed on a tissue sample (as opposed to being performed on the human or animal body), and so the claims were not excluded from patentability.

However, it is worth noting that the presence of a human or animal body during steps (1) to (3) of the method may still be implicit in the claim, even if it is not expressly specified. For example, in T125/02, a method for the diagnostic measurement of nitrogen monoxide content collected “during one or more exhalation phases in a sample of exhaled air” was considered unpatentable, because the wording of the claim implied that a patient must be present.

In contrast, in the recent decision T1920/21, a claim relating to a method comprising a step of measuring carbon isotope content in a breath sample was deemed not to require the presence of a human body. The Board noted that the skilled person would have known that breath samples can be collected in a breath bag, the specification described devices which could analyse breath samples in breath bags, and the wording of the claim did not require the presence of the patient. The method was therefore considered patentable. As summarised by the Board, whether a diagnostic method is excluded from patentability depends on “whether in the examination phase of the diagnostic method, the practitioner uses a diagnostic tool which measures a sample directly on (or in) a patient, or whether he uses a diagnostic tool which takes a sample from that patient which is subsequently analysed in a detector remote from the patient”.

When drafting applications with a view to prosecuting them at the EPO, if it is possible to carry out a measurement on a sample away from the patient, it may be helpful to clearly separate out the steps of collecting a sample and performing a measurement. It can also be useful to include descriptions of methods or devices which can carry out measurements on samples away from the patient (as in T1920/21).

It might be tempting to build in additional technical steps into a diagnostic method claim that are carried out outside of the human or animal body in order to escape the exclusion. However, only a technical step which is “constitutive for making the diagnosis” (i.e., which is or forms part of steps (1)‑(3) above) can exempt a diagnostic method from the exclusion when it is performed away from the human or animal body. In the assessment of the diagnostic character of a claimed method, it is irrelevant whether the claim includes additional, preparatory or intermediate steps that do not require the presence of the human body (T1197/02). For example, some Boards have decided that data processing in between data collection and comparison is a discrete intermediate step. As a result, in T143/04, the processing of collected data away from the human or animal body was not considered to render a diagnostic method patentable.

Finally, it is important to note that while diagnostic methods that meet the G1/04 test are not patentable at the EPO, the exclusion does not apply to products and compositions for use in such methods. It is therefore worth exploring whether diagnostic method claims can be reformulated into purpose-limited product claims (similar to reformulating method of treatment claims – a routine practice in Europe). For example, in T505/19, the Board allowed a claim to an antibody “for use in an in vivo method of diagnosis of inflammatory disease in the central nervous system”.

There are therefore many opportunities for applicants to secure useful claims directed to various aspects of diagnostic methods at the EPO that are not available at the USPTO. If you have any queries, then please do get in touch with our experienced Diagnostics & Personalised Medicine team.