<p class="first" id="P1">Research in the last decade has explored the length of telomeres,
the protective ends
of eukaryotic chromosomes, as a biomarker for the cumulative effects of environmental
exposures and life experiences as well as a risk factor for major diseases. With a
growing interest in telomere biology across biomedical, epidemiological and public
health research, it is critical to ensure that the measurement of telomere length
is performed with high precision and accuracy. Of the several major methods utilized
to determine telomere length, quantitative PCR (qPCR) remains the most cost-effective
and suitable method for large-scale epidemiological and population studies. However,
inconsistencies in recent reports utilizing the qPCR method highlight the need for
a careful methodological analysis of each step of this process. In this review, we
summarize each critical step in qPCR telomere length assay, including sample type
selection, sample collection, storage, processing issues and assay procedures. We
provide guidance and recommendations for each step based on current knowledge. It
is clear that a collaborative and rigorous effort is needed to characterize and resolve
existing issues related to sample storage, both before and after DNA extraction, as
well as the impact of different extraction protocols, reagents and post extraction
processing across all tissue types (e.g. blood, saliva, buccal swabs, etc.) to provide
the needed data upon which best practices for TL analyses can be agreed upon. Additionally,
we suggest that the whole telomere research community be invited to collaborate on
the development and implementation of standardized protocols for the assay itself
as well as for reporting in scientific journals. The existing evidence provides substantial
support for the continuation of telomere research across a range of different exposures
and health outcomes. However, as with any technological or methodologic advance in
science, reproducibility, reliability and rigor need to be established to ensure the
highest quality research.
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