considering the measurement of plasma glucose,
one of the most common biomarker tests. There
are many IVD methods for plasma glucose, but
they all comply with the traceability chain so that
the result obtained in the routine laboratory can
be traced back to a primary reference material
of pure glucose. As a result, there is excellent
agreement between methods for plasma glucose,
and results from elsewhere can be interpreted
with confidence.
For structurally simple molecules, like many
of those measured routinely in clinical chemistry,
pure substance is available, and it is possible to
have a complete unbroken traceability chain.
Even for some protein molecules it is possible
to achieve full metrological traceability by using
a unique, signature peptide as the primary
reference material. Consequently, there are
a growing number of important biomarkers
where method standardisation has been achieved
in a way comparable to plasma glucose.
Regrettably, most of the biomarkers measured
in laboratory medicine are not structurally simple
molecules. For example, complex proteins,
nucleic acids, viruses and bacteria are clinically
important biomarkers that may not be available
as pure substance and reference methods of
measurement are unlikely to be available. In
these circumstances full metrological traceability
is not possible. The adoption of international
conventional calibrators, with values assigned by
experts, represents traceability part of the way up
the chain and the use of such calibrators provides
a reference against which methods can be
harmonised to reduce between method variability.
The Joint Committee for Traceability in
Laboratory Medicine (JCTLM)
The JCTLM was established in 2002 through
a declaration between the International Bureau
of Weights and Measures (BIPM), the International
Federation of Clinical Chemistry and Laboratory
Medicine (IFCC) and the International Laboratory
Accreditation Cooperation (ILAC) in response to
the implementation of the European Community
Directive 98.79/EC on in vitro medical devices.
JCTLM currently has >50 members from 20
countries and its membership is growing rapidly.
The aim of the
JCTLM is to support
world-wide
comparability,
reliability and
Laboratory medicine specialists
equivalence of
should choose methods that are
measurement results
traceable to global standards to aid in laboratory medicine,
for improving health
the interpretation of patient results care and facilitating
national and
international trade in IVD devices, by:
• Promoting the concept of traceability of
measurement results
• Evaluating reference materials, reference
measurement procedures and reference
measurement services for laboratory medicine
with respect to conformity with appropriate
international standards;
• Facilitating the identification and prioritisation
of measurands requiring international traceability
and comparability and thereby encouraging
appropriate organisations to accept responsibility
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