Patentability of inventions relating to diagnostic methods at the EPO

Under Article 53(c) of the European Patent Convention (EPC), diagnostic methods practised on the human or animal body are excluded from patentability. The purpose behind this exclusion is to avoid patent infringement by medical and veterinary practitioners when carrying out a medical diagnosis. How Article 53(c) EPC should be applied was discussed in detail in the Enlarged Board of Appeal decision G 1/04.

In this decision, the Board held that the exclusion of diagnostic methods from patentability should be interpreted narrowly and sets out specific criteria for the assessment of this exclusion.

The Board held that a diagnostic method falls within the patentability exclusion set out in Article 53(c) EPC only if it includes all of the following steps (paragraph 5 of the Reasons of G 1/04):

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.

Thus, methods for obtaining intermediate results or findings, where no deductive medical or veterinary decision phase (“diagnosis for curative purposes stricto sensu”) is present, are not excluded from patentability under Article 53(c) EPC (paragraph 6.2.3 of the Reasons of G 1/04).

However, importantly, the Board explained that the exclusion from patentability of a diagnostic method cannot be circumvented by missing out one of the essential features of the method. This is because Article 84 EPC requires that, in order to be patentable, an independent claim must recite all the essential features which are necessary for clearly and completely defining a particular invention. In particular, the Board held that “the non-technical feature pertaining to diagnosis for curative purposes […] is to be included as an essential feature in the respective independent claim if its essentialness is unambiguously inferable from the respective European patent application or European patent as a whole” (paragraph 6.2.4 of the Reasons of G1/04).

As a further restriction, Article 53(c) EPC requires that, to be excluded from patent protection, a diagnostic method must be practised on the human or animal body. In this regard, the Enlarged Board held that “[t]he criterion ‘practised on the human or animal body’ is to be considered only in respect of method steps of a technical nature. Thus, it does not apply to the diagnosis for curative purposes stricto sensu, i.e. the deductive decision phase, which as a purely intellectual exercise cannot be practised on the human or animal body.” (paragraph 6.4.1 of the Reasons). The Enlarged Board concluded that “a claim is not excluded from patentability under [Article 53(c) EPC] if at least one of the preceding steps which are constitutive for making a diagnosis for curative purposes [i.e. at least one of steps (i), (ii) or (iii)] comprises a method step of a technical nature which does not satisfy the criterion ’practised on the human or animal body‘”.

The Board also explained that Article 53(c) EPC “does not require a specific type and intensity of interaction with the human or animal body”, and therefore a step of a technical nature “satisfies the criterion ’practised on the human or animal body‘ if its performance implies any interaction with the human or animal body, necessitating the presence of the latter” (paragraph 6.4.2 of the Reasons). This means that the interaction can be invasive or non-invasive, and non-invasive interactions may involve direct physical contact with the human or animal body or may be practised at a certain distance to it.

This criterion was discussed in recent Board of Appeal decision T 1920/21, where the claim at issue reads:

"1. A method for diagnosing a Helicobacter pylori infection in a patient treated with proton-pump-inhibitors (PPIs) comprising the steps of administering to the patient a mixture of citric acid, malic acid, tartaric acid in amount of 5 to 7 g, collecting a first breath sample, administering to the patient ¹³C-labeled urea, wherein the amount of ¹³C-labelled urea corresponds to 10 to 100 mg 99% ¹³C-urea waiting for a time of 10 to 60 minutes, thereafter collecting a second breath sample from the patient, measuring the content of ¹³C in the CO₂ of the first and second sample and determination of a ¹³C/¹²C ratio by spectroscopy in the respective samples characterized in that a difference Δδ of the ¹³C/¹²C ratio of the first breath sample and ¹³C/¹²C ratio of the second breath sample is calculated and the value of the difference in the range of 2 per mille to 2.9 per mille is used as a cut-off to indicate the presence of a H. pylori infection in the patient, wherein the method requires only a 1 day stop of PPI intake." (emphasis added)

In this decision, the Board held that the step of “collecting a breath sample” necessarily required the presence of the patient from which the breath sample was collected, and therefore that this step satisfied the criterion of “practised on the human or animal body”. However, the Board of Appeal was not satisfied that the subsequent method step of a technical nature involving “measuring the content of ¹³C in the CO₂ of the first and second sample and determination of a ¹³C/¹²C ratio by spectroscopy in the respective samples” met the criterion “practised on the human or animal body”. The Board concluded that it could not derive from the wording of the claim “any requirement that the measurement of these two samples also requires the presence of the patient”. As such, the Board concluded that the subject-matter of the claim was not excluded from patentability under Article 53(c) EPC since not all of the method steps of a technical nature were “practised on the human or animal body”.