Measuring up measurement methods – how to understand EPO patent parameters

Last week we examined the ‘unclear essential parameter trap’ where an application including a parameter that does not meet EPO standards may be refused, regardless of its substantive merit. This week we explore the various ways in which a parameter may be deemed unclear. 

Strict EPO practice is nothing new – the legal framework around the ‘unclear essential parameter trap’ is long established, although changes made to the EPO Guidelines in 2019 made this even more stringent. The changes essentially merged two sub-sections of the previous guidelines, incorporating the comments on measurement methods from previous F-IV, 4.18 into current F-IV, 4.11. Although in principle nothing much has changed, anecdotally, there are reports of more clarity objections to usual parameters than before. One can find reasons for this perceived stricter practice in subtle changes to guideline’s wording. Previous F-IV, 4.18 stated “In principle the method of measurement is necessary for the unambiguous definition of the parameter” (emphasis added). The term ‘in principle’ perhaps suggesting some flexibility in how the rule should be applied. In contrast, current F-IV, 4.11 states unequivocally “the method for measuring a parameter (or at least a reference thereto) must appear completely in the claim itself” (emphasis added). Moreover, the EPO has categorised the changes to the guidelines as part of “major amendments”, which had “substantially rewritten sub-sections on the practice regarding the use of parameters in claims”, implying a shift in practice.  

The guidelines provide two exceptions to the requirement for a measurement method to be included in a claim:

•    the measurement method to be employed belongs to the skilled person's common general knowledge (eg, because there is only one method, or because a particular method is commonly used); or 
•    all the measurement methodologies known in the relevant technical field for determining this parameter yield the same result within the appropriate limit of measurement accuracy.

Applicants may submit experimental data and/or expert declarations to prove one of these exceptions applies to a given parameter but this is not always possible. Accordingly, an examiner may insist that a claim is amended to include a method for measuring any parameters. Although this might seem a straightforward fix, there are many scenarios in which an application might appear to have been drafted in a reasonable way, but in practice is unsuitable for supporting such an amendment under EPO rules. 

Missing a measurement method

In one scenario, the application fails to include any reference to a measurement method; in such a case a claim cannot be amended to include one. This may occur if the parameter in question is considered ‘usual’ enough by the attorney and/or inventor such that no measurement method was included at the drafting stage. Although that would suggest one of the exceptions would apply, convincing an EPO examiner that this is the case is another matter. In particular, the omission of a measurement method at the drafting stage may be based on the gut feeling of ‘everyone knows how to measure that’, however such instincts must be substantiated with evidence to demonstrate one of the exceptions applies. This can be a particular problem for applications drafted outside Europe in a jurisdiction that has a more relaxed attitude towards the clarity of parameters and in which it is not necessary to include a measurement method for a ‘usual’ parameter. An application drafted with a parameter in claim 1 but without a measurement method in the description may be caught in the trap. 

A measurement method missing detail

In a second scenario, the application refers to a measurement method but fails to include sufficient detail to qualify as a clear parameter. Take molecular weight., there are many general methods for measuring this (eg, size-exclusion chromatography, gel permeation chromatography (GPC) and light scattering). An applicant might have considered referring to one of these methods sufficient to clarify a claim with a molecular weight parameter. However some decisions from the EPO Boards of Appeal conclude that the value of the molecular weight depends not only on the general measurement approach, but also on the specific conditions used for the measurement method (eg, T 541/09, followed in T 2063/12). Some cases conclude that the molecular weight obtained by GPC is highly dependent on conditions such as the sample concentration and calibration standard. Therefore, if an application merely refers to a generic way of measuring molecular weight, for example ‘molecular weight may be measured by GPC’, an objection could be made on the grounds that the parameter is unclear. An application drafted with a parameter in claim 1 and a measurement method in the description, but without enough detail on that method, may be caught in the trap. Indeed, we are seeing EPO examiners citing this case law in response to applications.

A measurement method incorporating trademarks

In a third scenario, the application includes a detailed measurement method but the level of detail leads to further issues. For instance, the method may refer to equipment or reagents by their trademarks. Amending a claim to include that measurement method may provoke further clarity objections because the guidelines only allow trademarks to be used in claims under very narrow circumstances (F-IV, 4.8). The use of trademarks in claims can also lead to insufficiency objections (F-III, 7). Accordingly, care must be taken when drafting all aspects of a measurement method, keeping in mind it may need to be incorporated into a claim in Europe. 

A standard measurement method

In a fourth scenario, the application has been drafted with reference to a standard measurement method for a parameter, for instance an International Organisation for Standardisation or ASTM International method. In many cases this approach is adequate, and the measurement method can readily be incorporated into a claim. The examiner is very likely to accept that a standard method contains enough information for the unambiguous measurement of the parameter without further investigation. However, for some standard measurement methods, a simple reference to the standard in the patent application may still fail to provide the level of detail required. For instance, the temperature at which a parameter is measured may affect the result. 

A standard measurement method may not mandate a single temperature at which to measure, instead, it may allow a range of possible temperatures but stipulate that the measured value should be reported along with the temperature at which it was measured. In such instances a basic reference solely to the standard method may not be enough to clarify a parameter, the temperature of the measurement must be specified as well (and possibly further variable conditions). 

Another example of this pitfall is the measurement of the glass transition temperature of polymers by differential scanning calorimetry in which the heating rate can affect the result. This can be a fatal flaw at the EPO. Patents have been revoked, even though they refer to standard testing methods, for not providing enough information on the measurement conditions (eg, T 412/02 and T 1252/08). Accordingly, an application drafted with a parameter in claim 1 and a reference to a standard measurement method for that parameter in the description, may still be caught in the trap.  

Next week, we will discuss a possible alternative approach to the EPO’s assessment of parameters, which may be more applicant friendly.