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Table 1 Overview of the phases of biomarker development and validationa

From: Revisiting the technical validation of tumour biomarker assays: how to open a Pandora's box

Phase Means/instruments Main challenges and sources of bias
Discovery of a potential
biomarker
Hypothesis-generating preclinical
or exploratory studies
Selection of biomarker based on the
availability of antibodies on the market
Development and technical validation of
the assay for the identification of the
biomarker
Optimisation of IHC-based assays for
formalin-fixed, paraffin-embedded
samples
- Use of clinical samples not suitable for
the analysis (for example core biopsies instead
of surgical samples and TMA instead of
full sections)
- Lack of reliable positive and negative
controls
- Poor fixation of clinical samples
- Wrong antigen retrieval procedure
- Wrong detection method Misinterpretation
of the results
- Training/competency of the staff
- Suboptimal performance of the antibody
due to poor fixation of archival tissues
(in particular for retrospective studies)
Validation of the clinical significance
of the biomarker
First retrospective studies and
subsequent prospective studies
- Training/competency of the staff
- Use of small cohorts or large cohorts
that include series of cases in which
the biomarker has been previously validated
Continued assessment of the
validity of the biomarker in
routine practice
Internal and external quality
assurance program
- Poor participation/adhesion to the
programme
- Lack of competency of pathologists
participating in the program
- No action taken if failing quality
assurance
  1. a Description of the phases of biomarker development and validation, and the main challenges and potential sources of bias, using immunohistochemistry-based
  2. assays as a paradigm.
  3. IHC: immunohistochemistry; TMA: tissue microarray.