Obviousness

Obviousness Analysis of U.S. Patent 11,738,124

Date of Analysis: May 13, 2026

Standard: An invention is unpatentable if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art (PHOSITA). This analysis is based on prior art available before the patent's priority date of May 30, 2017.

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Analysis of Independent Claim 1 (Method) and Claim 11 (System)

The independent claims of U.S. Patent 11,738,124 are directed to a method and system for plasma collection where the key inventive concept is the calculation of the "pure plasma" volume collected by accounting for the volume of anticoagulant mixed in with the plasma, using the donor's hematocrit in the calculation, and stopping the procedure when a target volume of this pure plasma is reached.

The claims would have been obvious to a Person Having Ordinary Skill in the Art (PHOSITA) by combining the teachings of a standard automated apheresis system with the well-established and widely published clinical knowledge regarding plasma volume calculations.

1. The Prior Art Baseline: Standard Apheresis Systems and Clinical Knowledge

• Basic Apheresis Systems: Prior to 2017, numerous patents, including many cited by the '124 patent itself (e.g., U.S. 4,086,924 to Latham, Jr. or U.S. 4,151,844 to Cullis, et al.), disclosed the fundamental components of an automated apheresis system. This established art included a venous-access device, pumps, a blood component separator (like a centrifuge), tubing, collection containers, and a controller to automate the process of drawing blood, separating components, collecting a desired component, and returning the remainder. These systems commonly used weight scales to monitor the volume of the collected product and stop the procedure when a target weight/volume was reached.

• Established Clinical Knowledge: It was common knowledge in the medical and apheresis fields that a donor's hematocrit (Hct) is the primary determinant of their plasma-to-red-cell ratio. Clinical guidelines and scientific publications available well before 2017 taught the explicit use of this information.

  • A 2014 article in the Journal of Clinical Apheresis titled "Calculations in apheresis" explicitly states, "By knowing the TBV [Total Blood Volume] and the Hct, the TPV [Total Plasma Volume] of the patient can be calculated." The article further explains how a donor's hematocrit directly influences the plasma collection procedure and the time required.
  • Standard medical procedure, as described in a Medscape article on plasmapheresis technique, involves entering the donor's height and weight into the system to estimate Total Blood Volume, and then calculating the plasma volume using the formula: Plasma Volume = TBV × (1 – hematocrit). This demonstrates that using donor weight and hematocrit to determine a target plasma volume was a routine and known practice.
  • Furthermore, the concept of accounting for the anticoagulant volume was also known. A presentation titled "Math in Donor Apheresis" notes that European collection guidelines specify that the maximum collected volume (e.g., 750 mL) is measured "exclusive of anti-coagulant." This teaching explicitly recognizes the distinction between the total volume in the collection bag and the "pure" plasma volume, and its importance for regulatory compliance and donor safety.

2. Motivation to Combine

A PHOSITA, such as a biomedical engineer designing apheresis equipment, would have been motivated to combine the known hardware of an automated apheresis system with the established clinical calculations for several reasons:

• To Solve a Known Problem: The '124 patent itself identifies the problem that collecting a fixed total volume results in inconsistent plasma yields from donors with different hematocrits. This was a known issue in the art. The 2014 "Calculations in apheresis" article details how hematocrit impacts collection, meaning a PHOSITA would have been aware of this inefficiency. Automating the known manual calculations directly addresses this known problem.
• Predictability of Results: A PHOSITA would have understood that programming a controller to perform the simple, algebraic calculations already being done manually or on external calculators would predictably result in a more standardized and accurate collection of pure plasma. The formula to calculate pure plasma is a straightforward subtraction: (Pure Plasma) = (Total Collected Volume) - (Anticoagulant Volume). The relationship between anticoagulant volume, whole blood processed, and the plasma fraction (1-Hct) was well understood. Implementing this logic in the system's controller would have been a routine design choice to achieve a more precise outcome.
• Automation of a Manual Process: It is a common and obvious path in engineering to automate routine, calculation-based tasks to improve consistency, reduce human error, and enhance efficiency. Since operators were already aware of and using the relationship between hematocrit and plasma volume to guide procedures, programming the system's controller to perform these same calculations is a classic example of applying automation to a known process.

3. Rendering the Claims Obvious

• Claim 1 (Method): All steps of the method claim were either part of standard apheresis or were well-known calculations in the art. A standard apheresis procedure already involved steps (a) through (g). The novel steps are (h) calculating the anticoagulant volume based on hematocrit, (i) calculating the pure plasma volume, and (j) continuing until a target pure plasma volume is reached. As established, the formulas and the scientific basis for these calculations were common knowledge. It would have been obvious to apply these known formulas to the data already available in an apheresis procedure (donor weight, hematocrit, anticoagulant ratio, and total collected volume) to achieve the more precise endpoint of a pure plasma target.

• Claim 11 (System): The system claim recites standard hardware components. The novelty lies in the configuration of the controller. As argued above, configuring a controller to perform the well-known plasma volume calculations and use the result as a stop condition for the blood pump is an obvious implementation. The controller is the logical component to house this calculation, and programming it to do so would have been a routine task for a PHOSITA aiming to improve the precision of the existing system based on known principles.

Conclusion

The claims of U.S. Patent 11,738,124 would have been obvious over the combination of a standard automated apheresis system and the well-established knowledge in the art concerning the calculation of plasma volume from a donor's weight and hematocrit. The motivation to combine these elements was strong and clear: to solve the known problem of inconsistent plasma yields and to automate a routine clinical calculation to improve the efficiency, accuracy, and standardization of the plasmapheresis process. The solution claimed represents the application of known principles to a known system to achieve predictable results.