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In , the Federal Circuit recognized the permissibility of using “about” to “avoid a strict numerical boundary” for a claimed parameter, but held the claims at issue invalid as indefinite under 35 U.S.C. § 112(b). The court’s analysis highlights that the flexibility of “about” comes with a risk of invalidity, especially when the scope of the claimed range cannot be ascertained from the specification and prosecution history with reasonable certainty.

The “About” Clauses At Issue

The patent at issue was U.S. Patent No. 10,912,321, directed to “Methods of using peracetic acid to treat poultry in a chill tank during processing.” The court considered claim 1, which recites in part (emphasis added):

1. A method of treating at least a portion of a poultry carcass with peracetic acid, said method comprising the steps of:

            …

            after the step of providing the peracetic acid-containing water, determining the pH of the peracetic acid-containing water, and altering the pH of the peracetic acid-containing water to a pH of about 7.6 to about 10 by adding an alkaline source;

            …

            after the step of placing at least the portion of the poultry carcass into the peracetic acid-containing water, determining the pH of the peracetic acid-containing water in the reservoir with at least the portion of the poultry carcass therein, and altering the pH of the peracetic acid-containing water to a pH of about 7.6 to about 10 by adding an alkaline source; and

            ….

The district court had found the “about” clauses to be indefinite. On appeal, the Federal Circuit agreed.

The Federal Circuit Decision

The Federal Circuit decision was authored by Judge Lourie and joined by Judge Prost and District Judge Burroughs (sitting by designation).

The Federal Circuit applied the legal standard of definiteness set forth in the Supreme Court’s 2014 decision in Nautilus, Inc. v. Biosig Instruments, Inc.:

A claim is invalid for indefiniteness if its language, when read in light of the specification and the prosecution history, fails to inform, with reasonable certainty, those skilled in the art about the scope of the invention.

Stepping through the intrinsic record (the claims, the specification, and the prosecution history), the Federal Circuit noted the following:

• The claims did not provide any guidance on the scope of “about”.
• Some of the examples reported in the specification indicated that “about” could mean ± 0.3 of a target pH, while others might support a broader scope, such as ± 0.35 or ± 0.5.
• The prosecution history did not inform the scope of “about,” especially where some arguments did not even use the term “about” when discussing the claimed pH range. The Federal Circuit found that the Applicant’s arguments “treated the term inconsistently, suggesting that it was material to some claims and immaterial to others.”
• The pH clause was amended to avoid prior art “which was as close as a pH of 7.0”

Summarizing its determination of invalidity, the opinion concludes:

When the specification recites pHs of 6–10, and the prior art pH of 7.0 required the claims to be amended, the definiteness requirement of § 112 necessitates much more clarity than using the vague term “about.” The prior art is almost “about” a pH of 7.6.

That last sentence strikes me as a finding of fact that begs for supporting expert testimony, even though Judge Lourie himself has a Ph.D. in chemistry.

What Was It All About?

The term “about” is used frequently in pharmaceutical patents where a degree of approximation often reflects reality more than strict numerical boundaries would, so I dug into the record to see what it really was all about. A few things struck me:

• The specification did not contain a general “definition” or explanation of “about.”
• The lower end of the recited pH range was pulled from specific examples, and was not expressly disclosed in the detailed description with an “about” modifier.
• The recited pH value was not the sole basis for distinguishing the prior art reference cited for disclosing a pH of 7.
• There were no parallel claims without the “about” modifier.

Regarding the Federal Circuit analysis, I was most struck by the court’s consideration of the precision with which the protocols of the examples were carried out. I appreciate that could inform how someone skilled in the art would have understood the recited pH values, but I wonder why the court decided that examples reflecting different magnitudes of variation from the target pH made “about” indefinite, rather than indicating flexibility up to the largest variation permitted.

Overall, this decision underscores that any flexibility in claim scope may carry a risk of invalidity for indefiniteness, even if precision in the parameter at issue is not critical to operability or patentability.