Art. 52(4) EPC 1973 (Art. 53(c) EPC) required that, to be excluded from patent protection, diagnostic methods had to be practised on the human or animal body. The Enlarged Board of Appeal held that in a diagnostic method, the method steps of a technical nature belonging to the preceding steps which were constitutive for making the diagnosis for curative purposes stricto sensu must satisfy the criterion "practised on the human or animal body".

This criterion was to be considered only in respect of method steps of a technical nature. Thus, it did not apply to diagnosis for curative purposes stricto sensu, i.e. the deductive decision phase, which as a purely intellectual exercise could not be practised on the human or animal body.

Art. 52(4) EPC 1973 did not require a specific type and intensity of interaction with the human or animal body; a preceding step of a technical nature thus satisfied the criterion "practised on the human or animal body" if its performance implied any interaction with the human or animal body, necessitating the presence of the latter.

Further, the grant of a European patent in respect of a diagnostic method which included preceding method steps of a technical nature carried out by a device did not contravene Art. 52(4) EPC 1973, because the performance of the respective method steps did not satisfy the criterion "practised on the human or animal body". However, in the event of patent protection, it would normally be sufficient to purchase the device in question in order to be entitled to carry out such a method. In cases where the same diagnostic conclusions could be reached by a method not including the use of the device, those carrying it out would not be inhibited by the patent. Therefore, medical or veterinary practitioners could not be considered to be hampered by the existence of such a patent.