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'Could versus would' approach to inventive step assessment in medical device case
  • Sep 30, 2021
  • Latest Journal

by Sarah Taylor and Belinda Lavin at Pinsent Masons

In a recent case concerning a patent directed to part of an ostomy bag (Coloplast A/S v Salts Healthcare Limited [2021] EWHC 3 (Pat)), the High Court considered the statutory approach to assessing obviousness in patent law, confirming that, ultimately, the question to be addressed is whether the claims involve an inventive step.

This decision, handed down in January 2021, is of interest to patentees in the life sciences sector, among others, as it brings to the fore the role of commercial attractiveness and technical limitations in whether an alleged invention may be considered to be lacking an inventive step.

The court held that in order to show obviousness, it is enough to show that the concept of the invention would have occurred to the skilled person, but they do not need to have implemented the idea. However, there may be technical rather than commercial reasons as to why the skilled person would not have implemented the invention, which may point towards an inventive step.

Ostomy bags are used to collect body waste discharged through an ostomy or stoma, which is an opening created surgically in a human body to allow the discharge of such waste. Given the nature of ostomy bags, they include a pouch made of impermeable material (the so-called 'barrier film').

Coloplast's patent was directed to a comfort layer, which is added to ostomy bags to overcome issues such as the pouch becoming damp and, therefore, uncomfortable for a user and to reduce the bag emitting rustling noises, which may embarrass users.

In April 2019 Coloplast launched infringement proceedings against Salts' Confidence BE range of ostomy bags. Salts in turn denied infringement and counterclaimed for revocation of the patent on the basis of the common general knowledge (CGK) and five pieces of prior art – namely, three patents and patent applications and two ostomy bags already on the market.

Interestingly, earlier in proceedings, the High Court had to deal with an application by Salts to stay the infringement proceedings given pending opposition proceedings at the European Patent Office (EPO). In a 2019 judgment, the court applied the 13 factors established in IPCom v HTC ([2013] EWCA Civ 1496) to consider when refusing or granting a stay. In refusing to grant a stay, the key factors relied on by the judge were the length of time for the EPO to reach a decision and the lack of certainty for patients in delaying the proceedings.

Skilled person and CGK

In the substantive proceedings, the court found that the skilled person would be a product developer or designer of ostomy bags who would be aware of the issues and needs faced by patients and the manufacturing processes used to make the bags.

In closing, Salts was critical of one of Coloplast's experts, who did not have experience in relation to ostomy bags; instead, the expert was more familiar with other types of product for collecting body waste. However, the judge rejected this criticism, holding that the expert was not and did not claim to be representative of the skilled person. The expert's expertise in materials (particularly the bonding characteristics thereof) meant that she was able to assist the court on matters which were central to the case.

CGK played a fundamental role in this case. The court held that at the priority date of the patent, the following matters were CGK:
• the use of comfort layers in ostomy bags;

• removable comfort layers made from woven materials and integrated comfort layers made from non-woven materials;

• the possibility of using woven materials for integrated comfort layers, although this had not been pursued due to cost and environmental disadvantages;

• the use of polyethylene or polyester for integrated comfort layers and the possibility of using polypropylene for integrated comfort layers; and

• the fact that the characteristics of the weld area surrounding an ostomy bag would depend on the material chosen and the three welding parameters of time, temperature and pressure.

Claimed invention
The court found that the claimed invention of the patent was that "[t]he patent for the first time teaches that a woven fabric can be used and welded in such a way to form an integrated comfort layer with improved properties".

Coloplast relied on the following alleged "improved properties":

• The strength of the bond between the comfort layer and barrier film meant that the skilled person could do away with the glossy weld of previous ostomy bags without compromising on strength.

• It was possible to achieve a weld zone whose surface both had the same visual and tactile characteristics as the rest of the comfort layer and was softer.

Finding of obviousness
The court found that the patent was obvious over the CGK and the five pieces of prior art relied on by Salts. Crucial to these findings was how the test for an inventive step or obviousness should be framed. Salts had placed emphasis on the fact that the invention should involve an inventive step whereas Coloplast had questioned this, pointing to the wording of the statute, which provides that an invention should be taken to involve an inventive step if it is not obvious to the skilled person.

The court agreed with Salts that "the issue is,  ultimately, whether the claims involved an inventive step". In coming to this conclusion, the judge referred to the so-called 'five-and-a-quarter inch plate paradox' (explained by Lord Justice Jacob in Actavis UK Limited v Novartis AG ([2010] EWCA Civ 82)) – namely, that although such a plate may be novel and not an obvious size, it cannot be patented as it does not involve an inventive step over known plates; it solves no problem and does not advance the art.

Another key finding of the court was the fact that it is enough to show that the alleged invention would have occurred to the skilled person and that it was not necessary to show that the skilled person would have actually implemented the idea (the 'could versus would' point). Importantly, whether the skilled person would actually go ahead and implement the alleged invention would depend on a host of other factors, including commercial considerations, which would have no bearing on the technical considerations that may indicate an inventive step.

As such, given that the judge had found that the possibility of using woven materials for integrated comfort layers was CGK at the priority date and that it had not been implemented merely due to commercial considerations (rather than technical reasons), the patent was held to be invalid for the lack of an inventive step over CGK.

The alleged improved properties were not enough to overcome an obviousness finding given that the judge had also found that it was well known that the characteristics of the weld zone would depend on the chosen material and welding parameters. Although the skilled person would have had to have carried out some experimentation to achieve a product that fell within the ambit of the claims, as the techniques to be used were a matter of CGK, the fact that some experimentation was required was not relevant.

In light of the finding of obviousness over CGK and the nature of the pieces of prior art relied on, it followed that a finding of obviousness over CGK would result in a finding of obviousness over the prior art, as the differences between the cited prior art and the alleged invention were those matters identified as CGK.

While the judgment does not provide any significant departures from the law of obviousness, it serves as a stark reminder that the ultimate question to be assessed is whether the claims involve an inventive step.

It does not matter whether the skilled person would actually have implemented the invention if there are non-technical reasons why they would not do so (eg, commercial factors such as cost or environmental considerations). The judgment indicates that if there are technical reasons as to why the skilled person would not have implemented the invention, that would assist in demonstrating that the claims are inventive.

The comments made by the judge in respect of the characteristics of expert witnesses in patent proceedings are noteworthy for practitioners in the life sciences sector. Patent litigators often grapple with how closely an expert's skills need to match those of the skilled person: an individual whose skills most closely match those of the skilled person may be viewed as lacking the required gravitas for an expert, but an individual who is a leading light in the relevant field may be considered 'inventive' and therefore more likely to find an invention obvious. The judge approved previous decisions which confirmed that expert witnesses do not need to represent the skilled person but must be able to assist the court with matters relevant to the issues in question and their reasons for their views. This perhaps leads to a fundamental consideration for solicitors when working with experts – namely, how well such experts communicate and justify their beliefs.

For further information on this topic please contact Sarah Taylor or Belinda Lavin at Pinsent Masons by telephone (+44 20 7418 8250) or email ( or The Pinsent Masons website can be accessed at

First published by the International Law Office

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