Rounding up or significant figures? - UK Court of Appeal holds that the broader interpretation should be used

What does the number 1 really mean?  This simple looking question has been put to the test by the UK Court of Appeal in Smith & Nephew Plc v ConvaTec Technologies Inc, relating to ConvaTec’s patent EP(UK)1,343,510.  The claim in question related to a process that specified an “agent being present in a concentration between 1 and 25%”, and the court had to decide whether a process using 0.77% of that agent constituted an infringement.

In the first instance proceedings, the High Court held that the number 1 should be construed to one significant figure, which makes the lower end of the range equivalent to 0.95.  However, Lord Justice Kitchin overturned this decision on appeal and held that the number 1 should be interpreted as covering values that round up to one, such as 0.5.  Based on this interpretation, the process using 0.77% of the agent was held to infringe.

When interpreting the claims, Kitchin LJ indicated that the “meaning and scope of a numerical range in a patent claim must [also] be ascertained in light of the common general knowledge and in the context of the specification as a whole".  When construing the claims, Kitchin referred to several parts of the specification that alluded to other amounts of the agent being suitable, such as between 0.01 and 50%, and noted that these disclosures teach “the skilled person that there is no technical reason to read the claim as requiring the use of a binding agent concentration which falls between the exact numerical values of 1 and 25%”.

While the decision should be welcomed as it is more in line with how the EPO typically interprets numerical ranges (such as in T234/09, para 4.3.2), the reasoning provided in the judgement makes it uncertain as to whether a different claim construction would have been used had the description been adapted into strict conformity with the claims.  In particular, the range of 1-25% was introduced into the claims after grant to ensure validity, but the description was never adapted to reflect these changes.  Had the description made no mention of other amounts outside of 1-25% and particularly amounts expressed using decimal places, it is possible that the Court of Appeal would have found no justifiable reason to overturn the first instance decision. 

The case therefore serves as a reminder of why interested third parties should insist that the description is amended to ensure consistency with the claims before applications grant or patents are maintained as amended in post grant proceedings. 

// Benjamin Hoffmann