Archived — Patent Notice: Examination Practice Respecting Medical Diagnostic Methods – PN 2015-02
From: Canadian Intellectual Property Office
June 29, 2015
To all examiners:
The examination of patent applications featuring diagnostic method claims presents certain challenges and warrants specific guidance to ensure efficient, predictable, and reproducible examination.
A diagnostic method outlines a sequence of steps to be followed to extract diagnostic meaning from data and will often comprise steps to:
- acquire data about an analyteFootnote 1 (e.g., identifying, detecting, measuring, etc. the presence or quantity of X in a sample); and
- analyze the significance of the acquired data (e.g., wherein the presence, increase/decrease of the quantity, etc. of X correlates to condition Y).
In order to determine the patentability of a diagnostic method claim, the examiner must take into account the general guidance on purposive construction introduced in PN 2013-02 - Examination Practice Respecting Purposive Construction (March 2013), which mandates that the evaluation of the subject-matter of a claim for compliance with section 2 of the Patent Act is to be made on the basis of the essential elements as determined through a purposive construction. In addition, it may be helpful to consult the guidelines articulated in PN 2013-03 - Examination Practice Respecting Computer-Implemented Inventions and PN 2015-01 – Revised Examination Practice Respecting Medical Uses.
This practice notice follows the purposive construction approach established above and provides further direction that is intended to facilitate the examination of diagnostic method claims specifically related to biological or medicinal inventions. The following practice is in effect immediately and in place of any contrary guidance.
Guidelines for analyzing claims to diagnostic methods
Identify the problem and solution
In order to initiate a proper purposive construction, an examiner identifies the problem the inventors set out to solve and the solution disclosed. An identification of the problem is guided by the description and the examiner's understanding of the common general knowledge in the art (not by reference to the closest prior art).
The examiner will give consideration to what the inventors state about the background of the invention, their objectives ("objects of the invention"), any specific problems, needs, limitations or disadvantages commonly known in the art or discovered by the inventors, etc. in identifying the problem faced by the inventors.
Common general knowledge
The common general knowledge (CGK) distinguishes the body of information widely recognised in the art from that which is simply publicly available and provides the baseline of information to which the description is expected to add. Thus, the person skilled in the art will read the specification in the expectation that it sets out something beyond commonly known solutions to commonly known problems. CGK that suggests that the problem was something different than that emphasized in the application must be considered by the examiner when identifying the actual problem solved by the invention.
Examiners should bear in mind that an application may describe more than one problem to be solved. For diagnostic methods, it may be appropriate to consider that an inventor is generally looking to solve a "data acquisition problem" and/or a "data analysis problem".
Where a "data acquisition problem" exists, the description will typically describe technical matter that goes beyond the CGK of the skilled person in the art. Factors in the description that may indicate the existence of a "data acquisition problem" include:
- a disclosure of a non-CGK analyte and method of identifying or quantifying the analyte;
- explicit statements that a specific problem or solution relates to how to identify or quantify a particular analyte;
- a significant level of detail devoted to describing the technical details of how data about a particular analyte is acquired; and/or
- an emphasis on the challenges or deficiencies of prior means to identify or quantify a particular analyte.
Factors in the description that may suggest that a "data analysis problem" exists include:
- explicit statements suggesting the problem to be solved is a "data analysis problem" or something other than a "data acquisition problem";
- placing an emphasis on the discovery of an allegedly new correlation between a condition and an analyte that is CGK with a relative absence of technical details pertaining to how to acquire the data about the analyte;
- indicators or explicit statements that, in order to acquire data about a particular analyte, it is CGK to apply the means contemplated by the application; and/or
- an absence of any explicit indication in the application that any practical problems were overcome relating to how to acquire data about an analyte that is CGK.
The solution is the element or set of elements that is essential to the resolution of the problem. If a claim includes solutions to more than one problem, examination should focus on one solution to a problem in performing the purposive construction. The initial choice of solution should be guided by the description, selecting the solution given the greatest emphasis by the inventors. If it becomes necessary to consider a different solution, the analysis should be undertaken anew.
Where a "data acquisition problem" has been identified, the solution is provided by those elements that provide a means to acquire data about an analyte. The means by which the data is acquired may be represented by either a single step or by multiple steps within the claimed method.
For example, elements relating to data acquisition may be represented by steps such as:
- detecting protein X in a subject sample;
- measuring the concentration of substrate X;
- determining the expression levels of genes A, B and C;
- contacting a urine sample with antibody A and determining the optical density; or
- incubating a sample with a nucleic acid probe consisting of SEQ ID NO:1 and detecting hybridization between the probe and target sequence Z.
Where a "data analysis problem" has been identified, the solution is provided by those elements that relate to the analysis of acquired data for the purpose of providing diagnostic meaning.
For example, elements relating to data analysis may be represented by steps such as:
- relating the presence of protein X from said test sample to a diagnosis of whether the test sample is from a subject suffering from disease Y;
- comparing the expression levels of genes A, B and C to a control standard, wherein a decrease in the levels as compared to the control is indicative of disease Y; or
- wherein hybridization of the probe to a target is indicative of the presence of disease Y.
Determine the essential elements of the claim using purposive construction
Having identified the problem and solution, a purposive construction of the claims involves interpreting the meaning of the various terms used therein as well as determining whether elements in the claims are essential (provide the solution to the problem) or non-essential.
Considering which elements are required to solve the problem, the examiner analyzes the claim to determine:
- those elements or set of elements that are essential to the solution; and
- whether all of the elements required for providing the solution are encompassed by the claim.
Where it appears that an essential element is missing from the claim, the claim may be defective for overbreadth (i.e., lack of support) and/or for lack of utility.
Recognizing that how data is analyzed or interpreted in a diagnostic method generally has no material effect on how the data needs to be physically acquired (and vice versa), the data acquisition elements and data analysis elements in the diagnostic method claim likely have a relationship reflecting an aggregation rather than a combination.
Where a "data acquisition problem" exists, the essential element or set of essential elements providing the solution is the means to acquire data about an analyte. If the identified problem does not relate to data acquisition then it will presumably relate instead to a "data analysis problem". Where this is the case, the essential elements will include steps relating to the mental analysis and/or intellectual significance of the data and will likely not include any steps to acquire the data since the way the data is acquired does not change the nature of the solution.
Determine whether the claim defines statutory subject-matter
Where a physical step of data acquisition is identified as an essential element of the construed claim, the claimed subject-matter will likely be statutory.Footnote 2 By contrast, a diagnostic method claim construed as consisting solely of essential elements that are disembodied (e.g., mental process, lacking physicality, no practical application, etc.) will be identified as defective for not complying with section 2 of the Patent Act. This would generally apply to situations where the identified solution is only provided by an element or set of elements associated with the analysis or significance of the acquired data (e.g., the correlation).
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