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Summary

Cell viability is often measured as a quality metric of tissue engineered medical products.  However, there are a number of inherent assumptions about cell viability measurements that make then difficult to discuss.  A “measurand chart” maps each of the measurands present in a measurement process to graphically represent their relationships and uncover the hidden assumptions. 

Description

Making a Measurand Chart: 

  • A measurand chart can be created for any measurement by writing down all the measurands that occur during the measurement.
  • The panels should not be procedural steps, such as “wash the sample with buffer” or “centrifuge the microfuge tubes”.
  • Consider if the measurement has a light source, a sensor, or a detector, since these will generate measurands.
  • If there is a numerical readout or generation of a data file, consider how these may be analyzed.
  • Think about equations that are used.
  • Identify the "primary measurand," which should plainly state what is being measured in only a few words.
  • Think about key assumptions.
  • Consider how the data will be used in terms of decision-making.
  • The panels should start with words such as “amount of”, “concentration of”, or “number of”.
  • Finally, the panels should be linkable by placing the words Measure the in front of the first measurand and by measuring between the rest.
  • These are not firm rules but guidelines. If the chart helps improve understanding of a measurement, then the goal is met.

 

Tissue engineering measurands figure

Definition of “Measurand”:

noun, the quantity or property intended to be measured

  • Use of the word “intended” in this definition is intentional
    • It may not be possible to measure what you intend to measure
    • Or you may not be measuring what you intend to measure (due to experimental artifacts) 
  • A measurement can have multiple measurands
  • Source: International Vocabulary of Metrology - Basic and General Concepts and Associated Terms (VIM), 3rd Edition. Joint Committee for Guides in Metrology (JCGM) 200:2012.

Definition of a “Viable Cell”:

noun, a cell that has 1) an intact membrane and the 2) capacity for metabolism, 3) motility, 4) proliferation and 5) reaction to stimuli

Slides: TE_measurands.pdf

Reference: Arora D, Babakhanova G, Simon Jr CG (2020) Tissue engineering measurands. ACS Biomaterials Science & Engineering 6, 5368-5376. https://doi.org/10.1021/acsbiomaterials.0c00475

Created July 6, 2021, Updated July 9, 2021