Lately, it has been very difficult to get diagnostic claims allowed without limiting the method steps to very specific components (e.g. reagents, devices, assays, samples, etc.). However, a recent Federal Circuit case suggests that there may be hope for broader diagnostic claims in the future. In Exergen Corp. v. Kaz USA, Inc., Appeal No. 2016-2315, 2016-2341 (March 8, 2018), the Federal Circuit upheld the district court decision that the claimed diagnostic technique was patent eligible under 35 USC §101. While the decision is nonprecedential, it shows that not all diagnostic claims are invalid as directed to a natural correlation or law of nature.

Claims 7, 14, and 17 of US Patent No. 6,292,685 (“the ’685 patent”) and claims 17, 24, 33, 39, 40, 46, 49, 60, and 66 of US Patent No. 7,787,938 (“the ’938 patent”) were at issue in Exergen. Claim 14 is representative of the method claims in the ’685 patent and reads as follows:

14. A method of detecting human body temperature comprising: detecting temperature at a forehead through a lateral scan across the temporal artery; and computing an internal body temperature of the body as a function of ambient temperature and sensed surface temperature.

Claim 14 is representative of the method claims in the ’983 patent and reads as follows:

14. A method of detecting human body temperature comprising making at least three radiation readings per second while moving a radiation detector to scan across a region of skin over an artery to electronically determine a body temperature approximation, distinct from skin surface temperature.

The Federal Circuit considered the two prong test under Alice (Alice Corp. V. CLS Bank Int’l, 132 S. Ct. 2347 (2014) and Mayo (Mayo Collaborative Servs v. Prometheus Labs, Inc., 132 S.Ct. 1298 (2012). The two prongs are 1) whether the claims at issue contain a patent ineligible concept (law of nature) and 2) whether they contain an “inventive concept” sufficient to transform the claimed abstract idea into a patent eligible application. In other words, if the claims recite only well understood, routine, and conventional activity, they do not constitute an inventive concept. There was no disagreement that the claims utilized a natural law (correlation between temperature readings from the forehead skin and core body temperature and the calculations used to determine the core temperature based on ambient and skin temperature). The question was whether the additional claimed steps were directed to a novel technique or added an inventive concept so that the claims were transformed into patent-eligible subject matter. The asserted claims recited at least one of the following steps: 1) moving while laterally scanning across the temporal artery, 2) obtaining a peak temperature reading, and 3) obtaining at least three readings per second. Though these claim elements were known in the art, they were previously used to detect hot spots indicating injury or tumors or surface temperature differentials. They were not used to detect arterial temperature beneath the skin. In addition, the prior art methods did not use the newly determined coefficient for translating measurements taken at the forehead into core body temperature readings. The district court found that there was no evidence that the claimed methods were well understood, routine, and conventional prior to Exergen’s invention. The Federal Circuit agreed, stating that “the inventor determined for the first time the coefficient representing the relationship between temporal-arterial temperature and core body temperature and incorporated that discovery into an unconventional method of temperature measurement” and thus, the method was found patent eligible.

The dissenting opinion stated that the claimed invention measures air temperature and the temperature of forehead skin directly over the temporal artery and then inputs these temperatures into a “heat balance equation,” which is a mathematical representation of the law of nature that governs the relationship between skin, air, and core temperatures. Devices for measuring temperature while laterally scanning an area were known in the art. Though the specific coefficient was not previously known, the inventors identified this coefficient through empirical testing of the coefficient that governs the relationship between core temperature and the temperature of the skin above the temporal artery. The dissent concluded that the calculations merely reflect the natural relationship between forehead and core body temperature, and thus the claims lack an inventive concept sufficient to transform them into patent eligible inventions.

It is clear from the dissent that there is still disagreement as to what makes a diagnostic claim patent eligible. Hopefully this will be cleared up as the Federal Circuit hears more challenges to patent eligibility decisions. In the meantime, it may be helpful to clearly indicate in the specification why the claimed combination of detection steps is not conventional, and to emphasize any transformations that occur as a result of the diagnostic method. Specific components used in the method steps should still be disclosed in the specification so that the claims can be limited to these components if the claims continue to be rejected as abstract ideas or natural correlations.