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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 them 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.
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