ISO 8934-1:2026

Biotechnology — Cell viability analytical methods — Part 1: General requirements and considerations

This document specifies the general requirements for cell viability analytical methods and for reporting cell viability. This document gives general guidelines for selecting and establishing fit for purpose cell viability analytical methods. This document specifies requirements for establishing standard operating procedures for cell viability analytical methods. This document also gives guidelines for managing sources of variability for cell viability measurements during pre-analytical, analytical, and post-analytical phases. This document is applicable to cells in suspension, cells adhered to a substrate, and cells in complex matrices. This document is primarily applicable to cell viability measurements of nucleated mammalian cells. NOTE 1 Several sector/application-specific international and national standards for cell viability currently exist. NOTE 2 When applicable, the user can consult existing standards when operating within their scope.

Biotechnologie — Méthodes d'analyse de la viabilité cellulaire — Partie 1: Exigences générales et considérations

General Information

• Status: Published
• Publication Date: 20-May-2026
• ICS: 07.080 - Biology. Botany. Zoology
• Technical Committee: ISO/TC 276 - Biotechnology
• Drafting Committee: ISO/TC 276 - Biotechnology
• Current Stage: 6060 - International Standard published
• Start Date: 21-May-2026
• Due Date: 25-Apr-2026
• Completion Date: 21-May-2026

Overview

ISO 8934-1: Biotechnology - Cell Viability Analytical Methods - Part 1: General Requirements and Considerations is an international standard developed by ISO Technical Committee 276 (Biotechnology). This document provides definitions, general requirements, and considerations for establishing and selecting fit-for-purpose cell viability analytical methods. It addresses sources of variability in cell viability measurements, such as those encountered during pre-analytical, analytical, and post-analytical phases, and offers guidance for managing these factors.

The standard primarily targets cell viability measurement for nucleated mammalian cells in various environments, including suspended cells, adherent cells, and cells within complex matrices. ISO 8934-1 supports laboratories, manufacturers, and researchers in ensuring reliable cell viability assessment, which is critical for cell-based research, product development, and regulatory compliance in biotechnology.

Key Topics

• Terminology and Definitions: Establishes common definitions for terms such as cell viability, analytical method, viable state, and quality attributes, ensuring consistent understanding across the biotechnology sector.

• General Concepts: Discusses foundational concepts for measuring and reporting cell viability, including distinguishing between count-based and non-count-based analytical methods and understanding viable state attributes.

• Fit-for-Purpose Methods: Provides considerations and guidelines for selecting and designing cell viability analytical methods to ensure they are suitable for their intended use, including sample preparation, measurement principles, and data analysis.

• Variability Management: Outlines strategies for identifying and controlling sources of variability at all stages of the measurement process:

  • Pre-analytical (e.g., sample collection, handling)
  • Analytical (e.g., reagents, instrumentation, environmental factors)
  • Post-analytical (e.g., data interpretation, reporting)

• Qualification and Validation: Recommends best practices for qualification, validation, and ongoing verification of cell viability analytical methods, emphasizing accuracy, repeatability, specificity, sensitivity, linearity, and robustness.

• Documentation and Reporting: Offers guidelines for establishing standard operating procedures (SOPs) and for comprehensive reporting of cell viability measurements to support traceability and reproducibility.

Applications

ISO 8934-1 is applicable in diverse areas of biotechnology and life sciences where precise cell viability measurements are essential. Key applications include:

• Basic Research: Supports studies in cell biology, physiology, and toxicology by providing standardized frameworks for viability measurements.
• Drug Discovery and Development: Assists pharmaceutical companies in evaluating compound cytotoxicity and efficacy.
• Manufacturing Control: Enables quality control in the production and batch-release testing of biologics, cell banks, and cell-based products.
• Cell Therapy and Regenerative Medicine: Facilitates the assessment of product potency, cell dose, and safety in the manufacturing and characterization of cellular therapeutics.
• Academic and Clinical Research: Provides foundational guidance to support reproducible results and compliance in laboratory and clinical studies worldwide.

Related Standards

Several international and national standards complement ISO 8934-1 in the field of cell viability assessment and analytical methods. Key related documents include:

• ISO 23033: General requirements for analytical procedures used in bioprocessing.
• ISO 20391-1 and 20391-2: Standards for cell counting and related cell measurement techniques.
• ISO 9000 Series: Quality management systems, including guidelines for validation and verification processes.
• ISO 21899: Standard operating procedures in laboratory practice.
• ISO/IEC Guide 99: International vocabulary of metrology-basic and general concepts.

When operating within specific application areas or sectors, users should consult relevant sector-specific or region-specific standards to ensure full compliance and optimal results.

---

By providing a unified approach to cell viability analytical methods, ISO 8934-1 helps standardize practices, reduce measurement errors, and facilitate global collaboration and innovation in biotechnology.

Standards Content (Sample)

International
Standard
ISO 8934-1
First edition
Biotechnology — Cell viability
2026-05
analytical methods —
Part 1:
General requirements and
considerations
Biotechnologie — Méthodes d'analyse de la viabilité cellulaire —
Partie 1: Exigences générales et considérations
Reference number
© ISO 2026
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or ISO’s member body in the country of the requester.
ISO copyright office
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Published in Switzerland
ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 9
5 General concepts of cell viability . 9
5.1 General .9
5.2 Cell viability analytical methods .10
5.2.1 General .10
5.2.2 Count-based cell viability analytical methods .11
5.2.3 Non-count-based cell viability analytical methods . 12
5.3 Cell viability as a measurand . 12
5.3.1 General . 12
5.3.2 Measurand charts for cell viability analytical methods . 13
6 Design of fit for purpose cell viability analytical methods .15
6.1 General . 15
6.2 Intended use . 15
6.3 Viable state attributes and measurement principles .16
6.4 Sample considerations and recommendations .18
6.5 Measurement process .19
7 Design of a matrix of cell viability analytical methods .20
8 Managing sources of variability in a cell viability analytical method .20
8.1 General . 20
8.2 Pre-analytical phase considerations .21
8.2.1 General .21
8.2.2 Presence of contamination (biological) . 23
8.3 Analytical phase considerations . . 23
8.3.1 General . 23
8.3.2 Test sample preparation . 23
8.3.3 Test sample stability .24
8.3.4 Analytical reagents .24
8.3.5 Environmental conditions . 25
8.3.6 Instrumentation and data collection . 26
8.3.7 Data analysis .27
8.4 Post-analytical phase considerations . 30
8.4.1 General . 30
8.4.2 Measurement uncertainty . 30
8.4.3 Reporting of cell viability .31
8.4.4 Metadata documentation .31
8.4.5 Interpretation of cell viability results .32
9 Cell viability analytical method qualification, validation, and continued verification .33
9.1 General . 33
9.2 Qualification . 33
9.2.1 Qualification characteristics . 33
9.2.2 Accuracy . 33
9.2.3 Repeatability . 34
9.2.4 Specificity and Selectivity . 34
9.2.5 Sensitivity . 34
9.2.6 Linearity and Proportionality . 35
9.2.7 Range . 35

iii
9.3 Validation . 35
9.3.1 Validation characteristics . 35
9.3.2 Intermediate precision . 36
9.3.3 Limit of detection (LoD) and limit of quantitation (LoQ) . 36
9.3.4 Robustness and Ruggedness .37
9.4 Continued verification .37
9.5 Quality control materials for cell viability measurements .37
Annex A (Informative) Examples of cell viability analytical methods and their viable state
attributes .39
Annex B (Informative) Example measurand chart for the luminescent cell viability analytical
method . 41
Annex C (Informative) Sources of cell stress that can affect the viable state of the cell .43
Annex D (Informative) Considerations for viability testing by pre-analytical treatment .46
Annex E (Informative) Considerations for cell viability as a quality attribute in the testing and
characterization of cellular therapeutic products .49
Annex F (Informative) Conceptual process for Cell Viability Analytical Method Development .51
Bibliography .53

iv
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 276, Biotechnology, Subcommittee SC 1,
Analytical methods.
A list of all parts in the ISO 8934 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

v
Introduction
Evaluation of cell viability is a fundamental measurement in biotechnology. Cell viability measurements
are widely and routinely used in basic research, drug discovery, toxicity testing, manufacturing control
and release testing for cell banks, biological products, and cellular therapeutic products. Cell viability can
be important in ensuring the safety and efficacy of cellular therapeutic products, in determining cell dose
and product potency in cellular therapeutic products, and in the manufacturing and control of cell-based
products and products derived from cells.
A quantity value for cell viability can be determined through a broad range of analytical methods evaluating
different attributes related to the viable state of the cell(s). Several biological properties, or attributes,
serve as the targets for identifying the viable state of the cell(s), and can be used to determine the viability
status of cells. Examples include observations of the cell’s membrane integrity, metabolic activity, nuclear
morphology, and a cell’s ability to replicate. Cell viability can also refer to different quantities related to
viable and non-viable cells including percent cell viability, viable cell concentration, and signals related to
the viable state. There is also a wide range of instrumentation used in the measurement of cell viability,
including image based, flow cytometry based, spectrophotometric, and electrical signal-based approaches.
Given the wide range of analytical methods associated with cell viability, it is often challenging to compare
cell viability results from different analytical methods without additional knowledge regarding the viable
state attribute investigated or the analytical method that was conducted. In addition, different applications
require the use of different cell viability analytical methods that are compatible with or relevant to the
intended use. Although cell viability standards exist, these standards are either test method specific, test
article specific, sector specific or region specific. Existing standards do not address the general need of
establishing common terminology for cell viability, considerations for fit for purpose cell viability analytical
method development and the reporting of cell viability measurement results.
This document establishes a common approach for defining fit for purpose cell viability analytical methods
to facilitate common understanding between users of the standard. This document provides general
concepts and terminology for cell viability measurements, provides considerations for measurement control
strategies and validation strategies, and considerations for establishing cell viability analytical method
standard operating procedures. This document also includes the establishment of a common framework for
reporting cell viability measurements.
This document is intended for a broad and worldwide industry where the quality and viability of cells are
critical for research and product development.
This part of the ISO 8934 series is focused primarily on mammalian cells.

vi
International Standard ISO 8934-1:2026(en)
Biotechnology — Cell viability analytical methods —
Part 1:
General requirements and considerations
1 Scope
This document specifies the general requirements for cell viability analytical methods and for reporting cell
viability. This document gives general guidelines for selecting and establishing fit for purpose cell viability
analytical methods. This document specifies requirements for establishing standard operating procedures
for cell viability analytical methods. This document also gives guidelines for managing sources of variability
for cell viability measurements during pre-analytical, analytical, and post-analytical phases.
This document is applicable to cells in suspension, cells adhered to a substrate, and cells in complex matrices.
This document is primarily applicable to cell viability measurements of nucleated mammalian cells.
NOTE 1 Several sector/application-specific international and national standards for cell viability currently exist.
NOTE 2 When applicable, the user can consult existing standards when operating within their scope.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
analytical method
investigative procedure for qualitatively or quantitatively measuring or assessing the presence, amount, or
functional activity of a target entity (the analyte)
[SOURCE: ISO 23033:2021, 3.3]
3.2
analytical method matrix
set of two or more complementary analytical methods (3.1) to measure different aspects of a quality attribute
(3.32)
[SOURCE: ISO 23033:2021, 3.7]
3.3
attribute
physical, chemical, biological, or microbiological property or characteristic
[SOURCE: ISO 20391-1:2018, 3.5]

3.4
attribute component
quantity used to derive a quality attribute (3.32)
[SOURCE: ISO 23033:2021, 3.9]
3.5
biological property
biological phenomenon that is evaluated to assess the quality attribute (3.32)
[SOURCE: ISO 23033:2021, 3.11]
3.6
bioprocessing monitoring mode
spatio-temporal position of a measurement device (i.e. sensor) or measurement process in relation to a
bioreactor or vessel
3.7
calibration
operation that, under specified conditions in a first step, establishes a relation between the quantity (3.34)
values with measurement uncertainties provided by measurement standards and corresponding indications
with associated measurement uncertainties and, in a second step, uses this information to establish a
relation for obtaining a measurement result from an indication
[SOURCE: ISO/IEC Guide 99:2007, 2.39, modified — Notes to entry deleted.]
3.8
cell concentration
cell count (3.9) per volume
Note 1 to entry: Typically used for cells in suspension.
[SOURCE: ISO 20391-1:2018, 3.6]
3.9
cell count
discrete number of cells
Note 1 to entry: Cell count is typically expressed as cell concentration (3.8) or area density.
[SOURCE: ISO 20391-1:2018, 3.7]
3.10
cell death
state of irreversible degeneration of vital cellular functions culminating in the loss of cellular integrity
Note 1 to entry: Definition based on Reference [5].
3.11
cell viability analytical method
investigative procedure for measuring or assessing the presence, amount, or functional activity of viable
cells (3.53), non-viable cells, other category related to viable state (3.55), or ratio thereof
3.12
examinand
nominal property (3.27) intended to be examined
Note 1 to entry: Definition based on Reference [7].

3.13
examination
process of experimentally obtaining one or more values that can reasonably be attributed to a nominal
property (3.27) together with any other available relevant information
Note 1 to entry: Definition based on Reference [7].
3.14
fit for purpose
in line with prearranged requirements for an intended use (3.17)
[SOURCE: ISO 20387:2018, 3.24, modified — Note to entry deleted.]
3.15
in-house reference material
non-certified material or substance, produced by one laboratory, one or more of whose property values are
sufficiently homogeneous and well established to be used for the intended use (3.17)
Note 1 to entry: The use of in-house reference materials can include, but is not limited to, validation (3.51), calibration
(3.7), monitoring of comparability, and potency and process evaluations.
[SOURCE: ISO 23033:2021, 3.24]
3.16
installation qualification
IQ
establishing by objective evidence that all key aspects of the process equipment and ancillary system
installation adhere to the manufacturer’s approved specification (3.45) and that the recommendations of the
supplier of the equipment are suitably considered
[SOURCE: ISO 23033:2021, 3.25]
3.17
intended use
use for which a product, process, or service is intended according to the specifications (3.45), instructions or
information or multiple of them provided by the manufacturer or user
[SOURCE: ISO 23033:2021, 3.26]
3.18
intermediate measurand
measurand (3.22) that is obtained as a part of the analytical method (3.1) where the quantity value (3.36) is
utilized by the user of the analytical method (3.1) but not reported as a quantity value (3.36) for the reported
measurand
3.19
intermediate precision
measurement precision under a set of intermediate precision (3.31) conditions
Note 1 to entry: The intermediate precision condition refers to the condition of measurement, out of a set of conditions
that includes the same measurement procedure, same location, and replicate measurements on the same or similar
objects over an extended period of time but can include other conditions involving changes (e.g. analyst or instrument).
[SOURCE: ISO/IEC Guide 99:2007, 2.23, modified — “measurement” was deleted from the term, note 1 to
entry has been added.]
3.20
limit of detection
lowest amount of analyte in a sample (3.43) which can be detected but not necessarily quantitated as an
exact value
[SOURCE: ISO 23033:2021, 3.29]

3.21
limit of quantitation
lowest amount of analyte in a sample (3.43) which can be quantitatively determined with suitable precision
(3.31) and accuracy
Note 1 to entry: The limit of quantitation is a parameter of quantitative analytical methods (3.1) for low levels of
compounds in sample (3.43) matrices and is used particularly for the determination of impurities (3.23) or degradation
products or both.
[SOURCE: ISO 23033:2021, 3.30]
3.22
measurand
quantity (3.34) intended to be measured
[SOURCE: ISO/IEC Guide 99:2007, 2.3, modified — Notes to entry and examples deleted.]
3.23
measurement principle
phenomenon serving as a basis of a measurement
Note 1 to entry: The phenomenon can be of a physical, chemical, or biological in nature.
[SOURCE: ISO/IEC Guide 99:2007, 2.4, modified — Notes to entry and examples have been deleted.]
3.24
measurement target
intended object of measurement
Note 1 to entry: A measurement target can denote a feature or complex features of cells that is informative of cellular
status or quality. The term is additional to the term analyte or measurand (3.22) in situations where the use of those
terms is not appropriate or possible.
Note 2 to entry: A measurement target can include both a measurand (3.22) and examinand (3.12).
[SOURCE: ISO 23033:2021, 3.21, modified – Notes to entry added]
3.25
membrane integrity
ability of a cell membrane to generate or maintain gradients of the concentration of specific target molecules
in solution
Note 1 to entry: Membrane integrity indicates metabolic activity of the cell but is not related to proliferation potential.
Note 2 to entry: The result of a membrane integrity test depends on the selected molecule.
3.26
metadata
data that define and describe other data
[SOURCE: ISO/IEC 11179-1:2023, 3.2.26]
3.27
nominal property
property of a phenomenon, body, or substance, where the property has no magnitude
Note 1 to entry: The nominal property is one for which only comparability by equivalence applies.
[SOURCE: ISO/IEC Guide 99:2007, 1.30, modified — Notes to entry and examples deleted.]

3.28
operational qualification
OQ
establishing by objective evidence process control limits and action levels which result in an analytical
method (3.1) that meets all predetermined requirements
[SOURCE: ISO 23033:2021, 3.33]
3.29
performance criteria
required functionality and behaviour of the test method (3.49)
[SOURCE: ISO 23033:2021, 3.34]
3.30
performance qualification
PQ
establishing by objective evidence that the analytical method (3.1), under anticipated conditions, consistently
meets all predetermined requirements
[SOURCE: ISO 23033:2021, 3.35]
3.31
precision
closeness of agreement between indications or measured quantity (3.34) values obtained by replicate
measurements on the same or similar objects under specified conditions
Note 1 to entry: Precision is usually expressed numerically by measures of imprecision, such as standard deviation,
variance, or coefficient of variation under the specified conditions of measurement.
Note 2 to entry: The 'specified conditions' can be, for example, repeatability (3.38) conditions of measurement,
intermediate precision (3.19) conditions of measurement, or reproducibility (3.40) conditions of measurement.
Note 3 to entry: Measured quantity value (3.36) refers to the quantity (3.34) value representing a measurement result.
[SOURCE: ISO/IEC Guide 99:2007, 2.15, modified — Term “measurement precision” was deleted and Notes 3
and 4 to entry were deleted.]
3.32
quality attribute
physical, chemical, biological, or microbiological property or characteristic that is an indicator of the quality
[SOURCE: ISO 23033:2021, 3.38]
3.33
quality control material
QCM
reference material (3.37) used for quality control of a measurement
[SOURCE: ISO Guide 30: 2015, 2.1.22]
3.34
quantity
property of a phenomenon, body, or substance, where the property has a magnitude that can be expressed
as a number and a reference
[SOURCE: ISO/IEC Guide 99:2007, 1.1, modified — Notes to entry and example were deleted.]

3.35
quantity formula
mathematical relation among quantities (3.34) in a given system of quantities, independent of measurement
units
[SOURCE: ISO/IEC Guide 99:2007, 1.22, modified — notes and examples were deleted and term changed to
"quantity formula".]
3.36
quantity value
value of a quantity
number and reference together expressing magnitude of a quantity (3.34)
[SOURCE: ISO/IEC Guide 99:2007, 1.19, modified — Notes to entry and examples were deleted.]
3.37
reference material
material, sufficiently homogeneous and stable with reference to specified properties, which has been
established to be fit for its intended use (3.17) in measurement or in examination (3.13) of nominal properties
(3.27)
[SOURCE: ISO/IEC Guide 99:2007, 5.13, modified — Notes to entry and examples deleted.]
3.38
repeatability
precision (3.31) of measurement under a set of repeatability conditions of measurement
Note 1 to entry: Repeatability conditions of a measurement refers to condition of measurement, out of a set of
conditions that includes the same measurement procedure, same operators, same measuring system, same operating
conditions and same location, and replicate measurements on the same or similar objects over a short period of time
(see ISO 23033:2021, 3.41).
[SOURCE: ISO/IEC Guide 99:2007, 2.21, modified — Term “measurement repeatability” was deleted and Note
1 to entry was added.]
3.39
representative sample
sample (3.43) that accurately represents or reflects the attributes (3.3) of the system
Note 1 to entry: Generally intended to provide information on the system, often to serve as a basis for decision on the
system or its production.
[SOURCE: ISO 23033:2021, 3.42]
3.40
reproducibility
precision (3.31) of measurement under reproducibility conditions of measurement
Note 1 to entry: Reproducibility conditions of measurement refer to the condition of measurement, out of a set of
conditions that includes different locations, operators, measuring systems, and replicate measurements on the same
or similar objects.
[SOURCE: ISO/IEC Guide 99:2007, 2.25, modified — Note to entry replaced and term “measurement
reproducibility” modified.]
3.41
robustness
measure of a test method (3.49) capacity to remain unaffected by small, but deliberate variations in method
parameters and provides an indication of its reliability during normal usage
[SOURCE: ISO 23033:2021, 3.44]

3.42
ruggedness
degree of reproducibility (3.40) of test results obtained by the analysis of the same samples (3.43) under a
variety of normal test conditions
Note 1 to entry: Normal test conditions can include for example: different laboratories, different analysts, different
instruments, different reagent lots, different analysis days, different elapsed times, different temperatures etc.
[SOURCE: ISO 23033:2021, 3.45]
3.43
sample
one or more parts taken from a system
[SOURCE: ISO 23033:2021, 3.46]
3.44
sensitivity
quotient of the change in an indication of a measuring system and the corresponding change in a value of a
quantity (3.34) being measured
[SOURCE: ISO/IEC Guide 99:2007, 4.12, modified — Notes to entry deleted and term “sensitivity of a
measuring system” revised.]
3.45
specification
document stating needs or expectations that are stated, generally implied or obligatory
3.46
specificity
characteristic of a test method (3.49) that expresses qualitatively and quantitatively its ability to detect or
determine an individual analyte without interferences from accompanying species
[SOURCE: ISO 23033:2021, 3.48, modified – Note to entry deleted.]
3.47
stability
characteristic of a material, when stored under specified conditions, to maintain a value(s) for stated
property(ies) within specified limits for a specified period of time
[SOURCE: ISO/TS 20399-1:2022, 3.17]
3.48
standard operating procedure
SOP
written procedure prescribed for repetitive use as a practice, in accordance with agreed-upon specifications
(3.45) aimed at obtaining a desired outcome
[SOURCE: ISO 21899:2020, 3.22]
3.49
test method
technical procedure used with a specified analytical method (3.1)
[SOURCE: ISO 23033:2021, 3.52]
3.50
test sample
small aliquot of the sample (3.43) that is prepared for measurement in the method of interest
Note 1 to entry: Generally, test samples are representative of the sample (3.43) they are prepared from and are
sometimes referred to as “representative test sample(s)”.

[SOURCE: ISO 20391-2:2019, 3.1.35]
3.51
validation
confirmation, through the provision of objective evidence, that the requirements for a specific intended use
(3.17) or application have been fulfilled
[SOURCE: ISO 9000:2015, 3.8.13, modified — Notes to entry deleted.]
3.52
verification
confirmation, through the provision of objective evidence, that specified requirements have been fulfilled
[SOURCE: ISO 9000:2015, 3.8.12, modified — Notes to entry deleted.]
3.53
viability
quantity or quantities (3.34) associated with the viable state (3.55)of cells within a cell sample (3.43) , that
is based on the measurement of a pre-selected viable state attribute(s) (3.56) that is (are) relevant to the
intended use (3.17)
Note 1 to entry: The viable state (3.55) of cells can change over time and can be heterogeneous within a cell population.
Thus, viability typically only represents the viable state (3.55) of a cell or of cells within a cell population at the time of
measurement.
3.54
viable cells
cells within a sample (3.43) that have an attribute (3.3) or attributes (3.3) of being alive (e.g. metabolically
active, capable of reproduction, possessed of intact cell membrane, or with the capacity to resume these
functions) defined based on the intended use (3.17)
Note 1 to entry: Non-viable cells can be considered those cells within a sample (3.43) that do not exhibit an attribute
(3.3) or attributes (3.3) of being alive based on the intended use (3.17).
[SOURCE: ISO 20391-1:2018, 3.29, modified — Note 1 to entry added.]
3.55
viable state
condition of a cell(s) related to an attribute(s) (3.3) of being alive
Note 1 to entry: The viable state can be described by a spectrum of attributes (3.3) related to vital cellular function and
cell death (3.10). Attributes (3.3) related to the viable state can include membrane integrity (3.25), metabolic activity,
molecular markers of cell injury, proliferative capacity, cell adhesion, cell motility, mechanical integrity of the cell,
reactivity to stimuli, cell or organelle morphology.
Note 2 to entry: Viable state can be applied to a single cell or a population of cells.
3.56
viable state attribute
physical, biochemical, or biological property (3.5) or characteristic that is an indicator of the viable state
(3.55) of the cell(s)
Note 1 to entry: In some applications, viable state attribute is referred to as the biological property (3.5) of the cell
viability analytical method (3.11).

4 Symbols and abbreviated terms
Abbreviated term or Description
symbol
AO Acridine orange
ATP Adenosine Triphosphate
CAR-T Chimeric antigen receptor T Cells
CQA Critical quality attribute
CRM Certified reference material
DAPI 4',6-Diamidino-2-phenylindole
DMSO Dimethyl sulfoxide
LDH Lactate dehydrogenase
LoD Limit of detection
LoQ Limit of quantitation
MTS 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium
N Viable cell count
N Total cell count
t
N Non-viable cell count
PBMC Peripheral blood mononuclear cell
PI Propidium iodide
PMT Photomultiplier tube
QCM Quality control material
RFU Relative fluorescence units
RM Reference material
SD Standard deviation
SOP Standard operating procedure
TUNEL Terminal deoxynucleotidyl transferase dUTP nick end labeling
V Viability, in %
5 General concepts of cell viability
5.1 General
Cell viability is a quantity associated with the viable state of cells and is based on the measurement of pre-
selected viable state attributes that are selected based on the intended use.
NOTE 1 Cell viability is sometimes discussed in the context of cell vitality. Cell vitality can be considered a subset
of cell viability where typically, vitality is a quantity(s) associated with viable cell state attributes that are not directly
indicative of cell necrosis.
NOTE 2 Cell viability is sometimes discussed in the context of cell health where cell viability is referred to as a
measure of cell health. Here the terminology of “cell health” is not used in order to avoid confusion with the pre-
analytical condition of the cells (e.g. the condition of the organism at the time the cells were isolated, for example cells
isolated from a “healthy” donor versus a “diseased donor). Cells from a diseased or “un-healthy” condition can still be
viable and non-viable.
Cell viability can be important in determining cell dose and product potency in cellular therapeutic products,
and in the control of manufacturing processes of cell-based products and products derived from cells.

Cell viability is also a common quantity measured in cell-based assays.
EXAMPLE An intended use of cell viability analytical methods can be to evaluate the cytotoxic effects of materials
(cytotoxicity can also be cell-mediated) in a cytotoxicity assay. The cytotoxicity assay measurement process includes
exposure of cells to potentially cytotoxic materials followed by testing of the cell sample with cell viability analytical
methods. There is often a temporal component to the cytotoxicity assay, where the cell viability measurements can
be taken at several time points after exposure to the potentially toxic material. Cell viability can be an intermediate
measurand in a cytotoxicity assay or the measurand itself.
5.2 Cell viability analytical methods
5.2.1 General
In a cell viability analytical method, one or more viable state attributes are evaluated to determine the viable
state of the cells and quantify the presence, amount or functional activity of viable cells, non-viable cells, or
other category related to viable state, or combination thereof.
In a cell viability analytical method, the definition of viable, non-viable, or other relevant category related to
viable state, should be based on the intended use.
NOTE Intended use in this context refers to understanding what attributes of viable state are critical for specific
applications (e.g. regulatory compliance, bioprocess monitoring).
Cell viability analytical methods that measure different viable state attributes, can result in different values
for measured cell viability with respect to both units of measure and biological implications. Selection of
the viable state attribute for a cell viability analytical method can impact the comparability of cell viability
results.
EXAMPLE 1 Membrane permeability, metabolic activity, and proliferation characteristics of cells can change at
different rates as the viable state changes and so evaluation of these different viable state attributes can result in
different conclusions regarding the viable state at any given time.
Different measurement principles can be used to evaluate a viable state attribute. Cell viability analytical
methods evaluating similar viable state attributes but utilizing different measurement principles can result
in different measured cell viabilities.
EXAMPLE 2 Cell viability analytical methods that indicate membrane integrity such as trypan blue and AO/PI can
derive different values for cell viability due to the size/shape of the indicator molecules, as well as the selectivity of the
indicators for nucleated versus non-nucleated cells.
Annex A provides examples of cell viability analytical methods.
Cell viability analytical methods can be based on cell counting methods (specifically differential cell
counting) or be based on non-count-based methods. When cell viability is based on cell counting methods,
it will have units of cells per volume or area, or be a unitless ratio of cell concentration values. When cell
viability is based on non-count-based methods it can have units based on the analytical target (e.g. lactate
dehydrogenase (LDH) concentration (g/L)) or be a unitless ratio of analyte concentrations.
Both count- and non-count-based methods can evaluate the same viable cell state attributes. This can
sometimes result in different cell viability quantity values even when the same attribute for viable cell state
is evaluated.
EXAMPLE 3 Both count-based and non-count-based cell viability analytical methods exist for evaluating the viable
cell state attribute of membrane permeability; however, the count-based method uses a membrane integrity dye to
enumerate membrane permeable and impermeable cells to evaluate cell viability (e.g. Trypan blue assay). The non-
count method evaluates the release of an analyte into the suspension media when cells lose membrane integrity
(e.g. LDH release assay). The amount of analyte released into the suspension media is correlated to the cumulative
number of cells that lost membrane integrity in the sample. Although both types of cell viability analytical methods
evaluate membrane integrity, the count-based method only accounts for cells that can be identified as viable and non-
viable entities, while the non-count-based method is an accumulation of information across cells that can be no longer
identifiable as individual entities (lysed cells). Therefore, cell viability quantity values resulting from these analytical
methods can differ.
5.2.2 Count-based cell viability analytical methods
Cell viability can be evaluated using differential cell counting analytical methods where viable, non-viable,
or other category of cells related to viable state, are selectively counted eithe
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