SIST EN ISO 20166-4:2021 PDF

Overview

EN ISO 20166-4:2021 defines requirements and recommendations for the pre‑examination (pre‑analytical) processes of formalin‑fixed, paraffin‑embedded (FFPE) tissue intended for in situ detection techniques. It is part of the ISO 20166 series on molecular in vitro diagnostic examinations and focuses on preserving tissue morphology and biomolecules (metabolites, proteins, DNA, RNA) for qualitative and (semi‑)quantitative in situ analysis. The standard is applicable to clinical and research settings that use FFPE sections for techniques such as immunohistochemistry, immunofluorescence, in situ hybridization (FISH/CISH), classical histology (H&E), and other histochemical methods.

Key topics and technical requirements

EN ISO 20166-4:2021 covers the full pre‑examination workflow with practical requirements and recommendations:

• Specimen collection and outside‑laboratory activities: patient/specimen information, processing prior to transport, labelling and intermediate storage.
• Transport and reception: handling, documentation, chain of custody and conditions for FFPE blocks and slides.
• Fixation and processing: formalin fixation practices, macroscopic evaluation, sample selection, decalcification/softening when needed, dehydration, paraffin impregnation and embedding.
• Sectioning and slide handling: block sectioning, storage of FFPE blocks and slide-mounted sections, deparaffinization and rehydration.
• Pretreatment for in situ methods: specific guidance for antibody/affinity binder‑based techniques and hybridization‑based assays (and other pretreatments relevant to in situ detection).
• Quality assessment: assessing pre‑analytical factors that affect in situ detection results.
• Supportive material: informative annexes with recommendations on verification/validation of laboratory‑developed in situ tests and example tissue‑processing protocols.

Note: the standard gives requirements and recommendations but does not cover pre‑examination of isolated nucleic acids/proteins (see ISO 20166‑1/2/3) or fine needle aspirates (covered in specific CEN WIs).

Applications and users

EN ISO 20166-4:2021 is designed for:

• Pathology and molecular pathology laboratories performing clinical in situ diagnostics (including laboratory‑developed tests).
• IVD developers and manufacturers creating assays and reagents for FFPE in situ detection.
• Biobanks, research institutions and commercial biomedical labs that collect, store or provide FFPE material.
• Regulatory bodies and laboratory customers seeking standardized pre‑analytical practices for reproducible results.

Practical benefits include improved reproducibility of immunohistochemistry and in situ hybridization results, better traceability of pre‑analytical variables, and standardized workflows that support companion diagnostics, digital pathology and multi‑label assay development.

Related standards

• ISO 20166‑1, ISO 20166‑2, ISO 20166‑3 (pre‑examination of isolated RNA, proteins, DNA)
• Relevant CEN WIs for fine needle aspirates and other specimen types

Keywords: EN ISO 20166-4:2021, FFPE, preexamination, pre‑analytical, in situ detection, immunohistochemistry, in situ hybridization, molecular in vitro diagnostic.