Table 1 Overview of the phases of biomarker development and validation^a

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