Federal Circuit Confirms Low Threshold for Finding That Prior Art Teachings are Analogous Art

September 10, 2014

What This Means to You

  • An argument that prior art teachings are not analogous art will be unlikely to prevail, particularly if some basis exists for the prior art to be reasonably pertinent to the problem faced by the inventor.
  • When seeking to invalidate a patent claim, consider prior art that may initially be thought of as outside the patent’s field of endeavor.


In Scientific Plastic Products, Inc. v. Biotage AB, the U.S. Court of Appeals for the Federal Circuit (Federal Circuit) confirmed the widespread notion that the threshold for determining what constitutes analogous art is low.

Case Background

Scientific Plastic Products sued Biotage for infringing three patents relating to low pressure liquid chromatography. Biotage requested inter partes reexamination of the asserted patents, staying the litigation. During the reexam, the patent examiner concluded that all of the asserted claims were obvious over the prior art. On appeal, the Federal Circuit affirmed the Patent Trial and Appeal Board’s finding.

The question on appeal was whether it would have been obvious to have modified the manner in which a liquid chromatography cartridge is sealed—in particular, by replacing the o-ring arrangement taught in one prior art reference, which is within the field of liquid chromatography, with complementary inclined sealing surfaces described in another prior art reference, which is within the field of soda pop bottles. The primary issue was whether a person of skill would have “looked” to combine elements of the prior art that are in different fields of endeavor; the actual ability to combine was not disputed.

Decision Analysis

In determining whether prior art references are analogous to the extent that one of skill would have even thought to have modified one teaching in view of another, the first inquiry to be made is whether the references are from the same field of endeavor, regardless of the problem. If so, then the references are analogous art. If not, then to qualify as analogous art, the references must be reasonably pertinent to the particular problem faced by the inventor such that a skilled artisan would have sought a solution outside the field (In re Clay, 1992).

Here, the court referred to the Background section of the asserted patents—which identified a leakage problem associated with conventional chromatography cartridges—and held that a skilled artisan would have looked outside the field of chromatography cartridges to find sealing solutions. While the secondary reference was not specifically related to liquid chromatography, it addressed the same fundamental issue of forming a fluid tight seal at elevated pressures. Hence, the art was found to be analogous and the claims were ruled as obvious.


Despite being a factual inquiry, it is not difficult to meet the threshold for finding prior art references analogous. Therefore, prevailing on an argument that prior art references are not analogous art will be uncommon. On the other hand, when seeking to invalidate a claim, it may be worthwhile to consider art from other fields of endeavor to form an obviousness rejection.

In addition, when drafting patent applications, much care must be taken in characterizing the prior art. In this case, the mention of a leakage issue in the background section of the asserted patents was taken as sufficient motivation to consider art from a technical field that may, on its face, seem unrelated.