The ‘How’ and ‘Why’ of Test
By Jim McGovern, TMV Consultant,
Test method validation (TMV) is the documented process of ensuring a test method is suitable
for its intended use. But TMV is not just
the process of performing Gage R&Rs.
Validation is about knowing the requirements, applying design controls, and
validating that the test method actually
performs as intended.
TMV is an important element of quality
control. Without validation, there can be
no assurance that the test results will be
reliable. Generally, any method used to
produce data in support of regulatory (e.g.,
FDA) filings or the manufacture of devices
for human use should be validated.
But TMV is more than just satisfying
regulations. The development and validation of a test method requires an overall
understanding of the materials, processes,
and design of the products being evaluated. It involves establishing the performance characteristics and limitations of a
method and the identification of influences that may change those characteristics.
The validation of test methods requires a
strong understanding of the uncertainty
of the test method. That uncertainty can
be random or systematic; personal, procedural, or instrumental. The experimental
results are subjected to statistical analysis
and a series of predefined acceptance
criteria are applied. Establishing that a
test method consistently produces reliable
results is a critical element of ensuring
product quality and safety.
TMV is a risk-based activity. The extent
of the activity is often dictated by the
potential level of patient harm weighed
against the business risk of not performing
the activities. The device risk index or
harm classification dictates the minimum
level of statistical confidence required.
Higher risk requires more rigorous testing.
Unlike analytical methods that may apply
to pharmaceuticals, TMV is not mandated
in the medical device industry (ISO 11607
testing is one exception). But demonstrating the safety and effectiveness of a device
is difficult to do if the methods for establishing these parameters are not shown to
be appropriate and reliable.
Test methods can be destructive or
non-destructive, based on the disposition
of the test samples. The methods can mea-
sure attribute data (qualitative) or variable
data (quantitative). All are candidates for
validation, though the process can vary.
Most test methods exist as validated standards, methods developed by technical
standard organizations to establish uniform procedures. But standard methods
do not always fit the requirements of the
tests to be performed. These test methods
may require validation:
• Standard (verifying lab version of standard is acceptable) — The lab specific
version of a method must meet or
exceed results of the standard
• Standard methods outside normal scope —
When using an established standard
for testing outside the original scope
of the standard
• Amplified/modified standard methods —
Validation of a version of a standard,
• Laboratory designed/developed —
Validation of a method developed
specifically for the test lab, to cover
a requirement not sufficiently met
by a standard
Method validation involves conducting
a variety of experiments that focus on
performance elements of the method to be
validated. Generally, a test method valida-
tion goes through the following phases:
• Determination of test specifics and
• Performing testing per protocol
• Results analysis
• Refining the test protocol and pro-
cedure if initial testing does not meet
pre-determined acceptance criteria.
This would be followed by execution
of the new protocol.
The level of activity in each phase of
the project is dictated by the customer
requirements of each particular method
Test method validation is becoming a more
closely scrutinized part of the development
and verification process. Establishing
that a test method consistently produces
reliable results is a critical element of
ensuring product quality and safety.