IP Information & News

English Court of Appeal confirms interpretation of 'about'

The interpretation of relative terms in claims is very often a part of patent infringement proceedings. Patent proprietors will often go for a broader interpretation of a relative term to attempt to encompass as much of an alleged infringer’s actions — and alleged infringers will often seek a narrower interpretation to navigate around a feature of a claim, so as to avoid infringement.

In many technical fields, particularly those involving chemical engineering and pharmaceuticals, numerical limitations can form part of claims and it is very often within the interests of a patent proprietor for numerical limitations to be as broad as possible whilst still proving a credible position from which to argue for novelty and inventive step.

One of the words often used in such numerical limitations is ‘about’, the meaning of which has now been given some interpretation at the UK courts. A claim, for example, may read: “A substrate comprising a first layer, wherein the thickness of the first layer is about 10 mm”. This claim is clearly trivial, but the question of what is within the scope of this claim is not.

If we extend this hypothetical scenario, consider an alleged infringer who is making a substrate with a first layer of thickness 13mm. Do they infringe the claim or not?

A similar issue was recently discussed before the Patents High Court and the English Court of Appeal.

High Court

Napp Pharmaceutical Holdings Ltd (Napp) is the proprietor of European patent (UK) No. 2305194 which relates to an invention of a transdermal patch for use in the treatment of pain. Napp alleged that Dr Reddy’s Laboratories Ltd (DRL) and Sandoz Ltd (Sandoz) threatened to infringe the patent and initiated proceedings before the High Court.

In the High Court, it was concluded that no infringement would have occurred if DRL and Sandoz had made their own proposed patches.

In the proceedings before the High Court, the Judge considered, amongst other things, what is meant by “about 10% wt- oleyloleate” as this was a feature of one of the claims of the patent. The precise formulations submitted by DRL and Sandoz were not publicised but they were not found to be infringing.

The judge held that the word ‘about’ should be taken to mean “a small degree of permitted imprecision over and above that implied by the usual rounding convention”. That is to say, about does broaden the numerical limit, but only above the usual rounding convention.

Court of Appeal

The construction of the word ‘about’ did form the basis of the appeal to the Court of Appeal and Napp filed a large number of arguments as to why the judge had erred in his construction of ‘about’.

The Court of Appeal upheld the High Court interpretation of the word ‘about’ and held that ‘about 10%’ did not extend beyond 9% at the lower limit and 11% at the upper limit.

Hypothetical example

Based on the Court of Appeal’s decision, the hypothetical infringer does not infringe, as the first layer is 13mm thick and is therefore outside the construction of the claim.


The Court of Appeal upheld that the word ‘about’ should be interpreted as admitting a small degree of imprecision over and above, using the usual rounding convention. However, this, perhaps inadvertently, introduces its own ambiguity to the meaning of the word.

Different fields will have differing rounding conventions. In some fields, “about 10%” will encompass 15% or 5% and in others it will exclude anything lower than 9.99% or anything higher than 10.01%. It is also often difficult to define the field in which a patent sits, so that rounding conventions can be established.

In order to avoid infringement where a claim of a patent specifies such a limit, it is clearly useful to assume a broader interpretation, unless there are strong commercial and technical reasons to consider otherwise.

If drafting a patent application where such limitations are important and likely to be significant in the definition of the invention, it is clearly useful to make it clear what you mean by ‘about’ — although there are reasons why an applicant would not want to make such admissions.

The Court of Appeal have provided guidance on the meaning of ‘about’ — but it is quite clear that the effect of such an interpretation is still fact dependent.

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