T 1423/22: Mathematical operations can contribute to technical character in diagnostic methods
In T 1423/22, the Board upheld a patent rejecting an appeal against the Opposition Division's decision. The claims related to methods for estimating glomerular filtration, a clinical parameter relevant in renal diseases, based on measuring the blood concentration of two markers (SDMA and sCr). The case centered on whether multiplying the two biomarker concentrations as part of a diagnostic method contained an inventive step. The Board determined that even non-technical features can contribute to inventive step when they interact with technical features to solve a technical problem.
Background
The patent at issue (EP 3041576) concerned a method for estimating glomerular filtration rate (GFR) in an animal subject by measuring concentrations of free symmetrical dimethylarginine (SDMA) and creatinine in a blood sample, and comparing the product of these concentrations to standard values that correlate to GFR. The opponent appealed against the Opposition Division's decision to reject the opposition, arguing primarily that the method lacked inventive step.
The Board’s reasoning
Regarding inventive step, the Board considered documents D1 and D6 as the closest prior art. The claimed method differed from the closes prior art in that it involved comparing a value resulting from an equation comprising the product of the blood concentrations of sCr and SDMA to one or more standard values that correlate to glomerular filtration rate in the animal subject to estimate the GFR and assess renal disease. This differentiating feature corresponds to steps (i) - (iii) of claim 1.
The Board rejected the appellant's argument that this distinguishing feature was merely non-technical and did not contribute to the method's technical character.
In this case, the mathematical operation (multiplication of two measured values) and mental act (comparison to standard values), though non-technical in isolation, contributed to the technical solution of estimating GFR.
The Board noted: "Step (iii), which is non-technical, contributes to solving this technical problem, together with measurement steps (i) and (ii), because the GFR estimated for an animal subject is determined by the recited calculation of a product of measured SDMA and sCr concentration values and a comparison of this product to one or more standard values that correlate to the GFR in the animal subject."
The Board further rejected the appellant's arguments that the claim involved "circular mathematical reasoning" or that the product of concentrations could encompass a ratio. It clarified that "a ratio is the result of a division, which is a different mathematical operation than a multiplication resulting in a product."
Decision of the Board
The Board concluded that the claimed method involved an inventive step regardless of whether document D1 or document D6 was used as the starting point. The approach of using the product of SDMA and sCr concentration values to estimate GFR was not obvious from the prior art, which at most suggested using both markers independently but not combining them by multiplication.
The appeal was dismissed, and the patent was maintained as granted.
Summary written by the NLO EPO Case Law Team