Parameters, i.e. new medical values or ranges, are typical limiting features of claims. In the following guidance shall be given as how to avoid pitfalls in the context of parameters and claims and their associated measurement methods.

1. Basics:

In order to avoid an enablement (Art. 83 EPC) trap with regard to parameter features in claims, it is required that

  • either the skilled person knows a measuring method for establishing the occurrence of the required properties in the real world, be it from the patent or from his/her general knowledge, and/or
  • the skilled person is aware of other measures (e.g. to be taken during the preparation of the claimed entity) inevitably resulting in the occurrence of the required properties in the resulting material (see e.g. 3.1 of the decision of the Technical Board of Appeal T0835/13).

If none of the two above requirements is met, there is typically an Art. 83 issue with regard to the claim containing the parameter.

2. What if a plurality of measurement methods for the parameter are known?

It is a typical scenario that the skilled person is aware not only of a single measuring method, or the patent does not explicitly state the mandatory use of one specified measurement method, but that there are a plurality of measurement methods. A plurality of measurement methods typically results in different values for the relevant property.

In the past, the EPO had taken the view (see e.g. T464/05 of May 14, 2007) that the absence of information in the application/patent regarding the method for measuring a crucial parameter implies substantial differences in the measured values obtainable when using one or the other of possible measuring methods known from the prior art. In the decision T464/05 this had been considered as being objectionable under Art. 83 EPC.

However, meanwhile the Boards of Appeal of the EPO have developed a more subtle approach (see e.g. T608/07 and T482/09 of 2009 and 2011, respectively). In T608/07 the Board had taken the view that an objection of insufficiency of disclosure (Art. 83 EPC) is only justified when the discrepancy in the measured values is of such magnitude that it “permeates the whole claim“ and „hence deprives the skilled person of the promise of the invention”.

The Board held that an insufficiency arising out of ambiguity is not enough to show that an ambiguity exists, e.g. at the edges of the claims. The effect of the ambiguity of the measurement methods has to be demonstrated “over the whole scope of the claim”.

In T482/09 the Board took the view that in case the parameter is a common parameter for which the skilled person is aware of several measurement methods, the uncertainty of a value of a recited parameter does not amount to an Article 83 EPC objection, but can of course impact other patentability requirements (i.e. the claim has to be interpreted in the broadest possible way including all possible measurement results, which obviously opens the claim to a wider field of prior art attacks).

3. Issues if a specific measurement method or device is mentioned in the claims Specific aspect decided in T1293/13: The claim refers to a specific particular method and to the use of a specific machine for implementing the measurement methods.

In T1293/13 the claim had a limitation as to a parameter (air permeability of a garment), wherein the claim referred to a particular measurement method and to the use of a specific machine (for measuring the air permeability).

To start with, the Board correctly had the view that the specific method and measurement machine are limiting features of the claims – any deletion thereof would thus lead to an illicit broadening of the scope of the granted claim.

In the decided case the measurement machine did no longer exist at the time of the decision. The machine was not only defined by its producer and/or type, but the claim even contained the serial number or model number of the machine, such that the Board held that the claim had an actual limitation that the parameter had to be measured with this very specific machine having the cited serial or model number.

The Board decided that the insertion of a feature defined as determinable by a specific machine, which in the decided case possibly had not – but certainly no longer – been publically available, led to the revocation of the patent for not being disclosed in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art (Article 83 EPC).