02 March 2010

A Lesson in Claim Construction

Case: Inverness Medical Switzerland GmbH v MDS Diagnostics Pty Limited [2010] FCA 108.

Inverness owns four patents related to a device for pregnancy testing at home. Inverness alleged that a number of respondents, collectively referred to as MDS, infringed its patents. The patents in question involved a parent with two divisionals and a separately filed patent. MDS challenged the validity of all four patents on the grounds of lack of utility and sufficiency.

To summarize the result:
  1. Claim 1 of the first patent is infringed.
  2. Claim 1 of the second patent is infringed.
  3. Claims 1 to 4 of the third patent are invalid for lack of novelty. The third patent has expired.
  4. Claims 1 and 22 of the fourth patent are invalid for lack of novelty and should be revoked.
  5. Dr Appanna is personally liable for the infringement as a joint tortfeasor.
  6. Dr Appanna is liable under s 13(1) of the 1990 Act for authorising infringement.

Claim Construction

Key issues were the meanings of certain terms. One of those terms was "specific binding reagent" which appeared as part of an essential integer of the claims. This term was important because it appeared that the only difference between the MDS kits and the example in the first patent was that the antibodies are reversed in the MDS kits. Inverness said that the reverse use of the antibodies made no difference.

Inverness asserted that the term meant the reagent could bind not only to the analyte sought to be detected, but also to other molecules related to the analyte. MDS asserted that the reagent will preferably bind only to the analyte and to no other molecule in the sample. Bennett JJ found that normal English usage in the field of immunology supported both positions. So she turned to the specification of the parent patent. She held that the specification appeared to draw a distinction between specificity and a specific binding reagent. "Specificity" defines the ability of the reagent to identify only that reagent. "Specific binding reagent" defines the characteristic that ensures that the reagent does bind with the analyte in a specific way. For example, the specification recognised the existence of cross-reactive immunoassays and made reference to antibodies that would cross-react with molecules other than the target antigen. That is, the reagents were not absolutely specific. MDS countered by finding examples in the specification where the word "specific" was not used, such that the use of that word would indicate a preferable binding. But Bennett held that it was equally likely that the claim included rather than excluded a particular embodiment of the invention. She did not accept that there was a deliberate differentiation. Furthermore, she pointed out that the specification used the term "highly specific" which did not mean "mono-specific".

In summarising this part of the judgement, Bennett held that the "untutored" approach of using the word "specific" as an adjective to describe a type of binding reagent should be rejected. The reasons included the manner in which the specification used the expression "specific binding reagent". The specification recognised the concept of degrees of specificity. The specification set out examples of antibodies which were not mono-specific.

Another term which was relevant was "dry porous carrier". It was part of an essential integer of the four patents. Inverness said that the specification focused on the function of the carrier rather than on the physical form of the carrier. So the term covered a single body or a number of discrete bodies. MDS on the other hand said that the term was limited to a a single continuous piece of material. The term was important, because the MDS device contained a number of dry, porous discrete pieces.

Bennett pointed out that the specification referred to the the carrier as a strip or sheet, but only as a preferred embodiment. The term was used in claim 1. Claim 9, dependent on claim 1, limited the carrier to a strip or sheet of porous material. This meant that claim 1 envisaged a broader interpretation. So she found that the MDS device contained a dry porous carrier within the meaning of claim 1.

Claim 1 of the first and second patents were found to be infringed.

Yet another term which came under scrutiny in the third patent was "within said casing". The claims of the third patent contained the integer of a ‘bibulous sample liquid receiving member within said casing to receive sample liquid applied to said application aperture’. The issue was whether the word "within" meant only "wholly within" as contended by MDS or also "partly within" as contended by Inverness.

MDS relied on the Oxford English Dictionary meaning of "within". Inverness responded by pointing out that figures 8 and 9 in the specification showed an embodiment with the sample member protruding from the casing. Bennett pointed out that the specification did not use the word "within" when describing figures 8 and 9. However, the specification did use the word "within" when describing a position of a carrier strip depicted as wholly within a casing. So Bennett concurred with MDS.

Inverness alleged that MDS also infringed claims that contained "porous material backed with transparent moisture-impervious material". MDS contended that its product did not take this integer because it was coated with a strip of white vinyl which was not transparent. Also the white vinyl did not perform the same function as the transparent material. Bennett concurred with MDS.


One test of utility is whether the claimed invention fulfils the promise of the specification, in that it does what was intended and claimed by the patentee (Advanced Building Systems Pty Ltd v Ramset Fasteners (Aust) Pty Ltd [1998] HCA 19; (1998) 194 CLR 171), and whether the end obtained is itself useful (Ranbaxy Australia Pty Ltd v Warner-Lambert Co LLC [2008] FCAFC 82; (2008) 77 IPR 449)

Bennett pointed out that the claims should be construed as they would be by the person skilled in the art desirous of making use of the invention. Furthermore, a claim does not need to specify a limitation that was common knowledge in the art for that limitation to apply in construing a claim to avoid want of utility. Where a claim omits a feature which proper construction leaves for the reader to supply, the claim will not be invalid for want of utility if the feature is one that the skilled addressee could reasonably be expected to supply to make the invention useful. 

Bennett said that the invention would be useful if the specific binding reagents were chosen such that, in combination, they were selective for the desired analyte. Inverness asserted that a person skilled in the art would be capable of selecting appropriate specific binding reagents. The specification of the first patent was silent on accuracy.

MDS said that what was promised in the first patent and claimed in claim 1was an analytical device which would function as an analytical device for the targeted analyte and, from that, accuracy is necessarily a promise.

But Bennet said that the fact that, in theory, one could construct a device according to the claims that, in certain circumstances, would not detect the analyte is insufficient to render the claims invalid for want of utility.


The test for sufficiency is whether the disclosure in each of the patents enables the skilled addressee to produce something in each claim without new inventions or additions or prolonged study of matters presenting initial difficulty.

MDS contended that, on the construction of "specific binding reagent for an analyte", the first, second and fourth patents were invalid for insufficiency. According to Bennett, MDS in effect submitted that the claimed device of each of the patents is to test for an analyte with no cross-reactivity and no false positive or negative results, so that a device within the claims is not possible in the absence of scavenger molecules.

Bennett pointed out that the claims of the patents are not limited to devices which give no false positive and no false negatives. There was no evidence that the skilled worker could not make the inventions as claimed or that he or she would make a device that failed to detect an analyte.


MDS contended that claim 1 of the second patent and claim 22 of the fourth patent were invalid for want of clarity. Claims are required to define the invention clearly and succinctly so that readers can ascertain the precise extent of monopoly claimed. If a claim is ambiguous, the ambiguity may be resolved by reference to the body of the specification. Failing that, the claim is invalid. MDS contended that the following words in claim 1 of the second patent were not clear or capable of any sensible meaning: "..the device also containing a labelled specific binding reagent for an analyte, or which can participate in a competition reaction in the presence of an analyte....". Inverness explained that this passage referred to two types of labelled specific binding reagents. One of the expert witnesses gave evidence that she understood the words in that way. Bennett said that made sense and was consistent with the disclosures in the specification.

MDS also contended that "having" was not clear in "the labelled antibody having freely mobile within the macroporous body and the porous carrier when in the moist state."  Bennett pointed out that in an almost identical passage in the body of the specification, the word "having" was replaced by "being". A reader wishing to clarify the meaning of the passage would go to the specification and see that the word "having" should be replaced by "being". So there was no lack of clarity.

Priority dates

There is a useful discussion of  the requirement of "fair basis" as it applies to priority dates. I won't discuss that in this post because I have already considered a number of the cases cited in that discussion. I also wanted to limit this discussion to claim construction, in particular.


This case is worth reading because it gives some practical guidelines on claim construction. It is a reminder of the strong connection between the claims and the body of the specification and of the fact that one cannot properly be considered in the absence of the other.

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