Revenge of Significant Figures

A recent federal circuit case brought to bear something many of us thought we left behind in high school. Significant figures. If they were confusing to you then, you probably aren’t alone, and I shudder to contemplate these attorneys and judges (re)mastering the concepts for this lawsuit. But here we are!

In AstraZeneca AB v. Mylan Pharmaceuticals Inc., the issues were more about infringement than claim construction. At the district court level, the court construed “0.001%” according to its “plain and ordinary meaning, that is, expressed with one significant digit.” The Federal Circuit summarized the issue before it succinctly:

The question here is whether the concentration of PVP being “0.001%” means 0.001% within one significant figure—encompassing a concentration of PVP in the range of 0.0005% to 0.0014%, as AstraZeneca contends and as the district court construed this term—or it has a narrower meaning in view of the specification and the prosecution history—precisely 0.001% w/w PVP with only “minor variations,” as Mylan contends. 

So at the district court level, the court held that, “[b]ased on the rules of rounding, the court determined that the plain meaning of the term ‘0.001%’ encompassed the range of 0.0005% and 0.0014%.”

But the Federal Circuit took an approach that more holistically considered the patent’s specification. In this instance, the specification compared 0.001% against 0.0005%, which otherwise would have been within the rounding error. At least in part because of that comparison, the Federal Circuit rejected the district court’s approach. Finally, the Federal Circuit noted that the patentee could have used the term “about” to extend the range of the disclosed values.

What’s the lesson here? The lesson is, once again, to be careful about numerical ranges and values surrounding them. When patent practitioners draft patents, they may need to be obnoxious with language. Make all number values (where appropriate) modifiable by “about,” and make sure there is disclosure of relevant number ranges when possible and appropriate.