Patents and parameters – challenges associated with standard measurement methods
Referring to a standard measurement method, e.g. an ASTM, can be an attractive way to minimise risks associated with parameters. However, care should be taken to avoid leaving weaknesses in a patent

EPO practice is strict on the assessment of parameters in claims, often requiring that a method for measuring the parameter is also included in the claim. Including a reference to a standard measurement method set by an international body, such as an ASTM standard or an ISO standard, can be an attractive way to address this issue. However, care must be taken when following this approach to avoid leaving weaknesses in the patent.

A parameter is a property which is defined by a numerical value.  Common examples include tensile strength, viscosity, and particle size. It is often useful to use parameters in claims to distinguish an invention from the current state of the art, particularly in the fields of chemistry and materials science. EPO practice has long been strict on the examination of the clarity of parameters. This has been reinforced by the latest revisions to the EPO’s Guidelines for Examination, in particular Section F-IV, 4.11, which was revised in November 2019. The Guidelines now require that a method for measuring a parameter must appear completely in the claim itself for that parameter to be clear. There are exceptions to this rule; however, these are narrow exceptions which are typically rigidly enforced by EPO examiners.

This strict practice extends to the assessment of sufficiency as well as clarity. A claim including a parameter with a missing or incomplete measurement method can be found to be insufficiently disclosed. There are many examples of this in the EPO’s case law, for example relating to particle size or viscosity parameters. This is an important part of EPO practice since a patent may be challenged after grant for being insufficiently disclosed but it cannot necessarily be challenged for being unclear.

To reduce the risks of a parameter being deemed unclear and/or insufficient by the EPO, one approach when preparing a patent application is to include a reference to a standard method set by an international body for measuring that parameter. For example, both ISO (the International Organization for Standardization) and ASTM (formally known as the American Society for Testing and Materials) provide measurement methods for a very wide variety of parameters. A statement can be included in the description indicating which standard method to use, for example “Parameter X is measured according to ASTM‑xxxx”.

In many cases this approach is adequate. The measurement method can be incorporated into a claim if needed to satisfy an EPO examiner that the parameter is clear. The examiner is likely to be convinced that a standard method contains enough information for the unambiguous measurement of the parameter. However, this may not be the case for all standard measurement methods. A basic reference to some standards may arguably still be missing essential information.

For instance, the temperature at which a parameter is measured may affect the result. A standard measurement method may not specify a single temperature at which to measure; instead, it may state a range of possible temperatures and that the 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). This is an important issue at the EPO. Patents have been revoked, even though they refer to standard testing methods, for not providing enough information on the measurement conditions (e.g. T 412/02 and T 1252/08). Nevertheless, the lack of explicit information may not be the end of the road for a patent, as it may be possible to infer the appropriate conditions from other information in a patent specification and from the skilled person’s common general knowledge. In any case, it is good practice to carefully review at the time of preparing a patent application any standard measurement methods used to ensure that any ambiguous conditions are specified, for example “Parameter X is measured according to ASTM-xxxx at 25 °C.

A further issue is that standard measurement methods are updated periodically and may thus change over the lifetime of a patent. EPO practice indicates that trademarks may be deemed unclear or even insufficient because their meaning may change over time (see Guidelines, F-IV, 4.8 and F-III, 7). By analogy, a standard measurement method could be deemed unclear or even insufficient for the same reason. To avoid this risk it is good practice to refer to a specific version or year of a standard measurement method, for example “Parameter X is measured according to ASTM‑xxxx-yyyywhere yyyy is the year that the standard was published. Again, it could be argued that the common general knowledge of the skilled person can be used if this information is lacking in the patent. However, prudent patent preparation would avoid the need to rely on such arguments.

In summary, it may be convenient to refer to standard measurement methods in view of strict EPO practice on the clarity and sufficiency of parameters. However, care should be taken that the standard contains enough information to allow the unambiguous measurement of the parameter. Merely referring to a standard method alone may still leave avoidable weaknesses in a patent.

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