Overview
ISO 20166-3:2018 - “Molecular in vitro diagnostic examinations - Specifications for pre‑examination processes for formalin‑fixed and paraffin‑embedded (FFPE) tissue - Part 3: Isolated DNA” provides standardized guidance for the pre‑analytical handling of FFPE tissue intended for DNA analysis. The document defines requirements and recommendations for specimen collection, fixation, processing, documentation, storage and DNA isolation to preserve DNA integrity prior to molecular in vitro diagnostic (IVD) testing.
Key topics and technical requirements
- Pre‑examination scope: Covers the full pre‑analytical workflow from clinician request through to the start of the analytical DNA assay (collection, transport, reception, processing, storage and isolation).
- Formalin fixation and NBF: Defines standard buffered formalin (NBF: 10 % formalin, ~3.7 % mass fraction formaldehyde, pH 6.8–7.2) and addresses fixation practices that influence DNA quality.
- Terminology and conditions: Includes terms such as cold ischemia, warm ischemia and room temperature (defined as 18 °C–25 °C) relevant to pre‑analytical control.
- Specimen handling & documentation: Requirements for accurate donor/patient and specimen information, chain‑of‑custody, transport conditions and reception records.
- Processing steps: Guidance on grossing, decalcification, paraffin embedding, tissue processing and post‑fixation of frozen samples to minimize artefacts affecting DNA.
- Isolation of DNA: Recommendations for DNA extraction from FFPE blocks, including use of commercial kits versus in‑house protocols and the need for validated methods.
- Quality control: Procedures for DNA quantity and quality assessment and appropriate storage conditions for isolated DNA.
- Risk factors: Addresses chemical modifications from fixation, fragmentation, methylation changes and potential impacts on downstream assays.
- Annex: Informative material on how storage temperature affects DNA integrity in FFPE blocks.
Practical applications
- Ensures reliable, reproducible molecular diagnostic results by minimizing pre‑analytical variability that affects DNA integrity.
- Guides laboratory SOP development for pathology, molecular diagnostics and biobank workflows.
- Supports validation and verification of laboratory‑developed tests and IVD kit performance on FFPE material.
- Useful for quality managers, clinical laboratory staff, molecular pathologists, biobank curators and regulatory reviewers.
Who should use this standard
- Medical laboratories and molecular pathology labs performing in‑house or commercial molecular tests
- IVD developers and manufacturers
- Biobanks, academic and commercial research organizations
- Regulatory authorities and accreditation bodies overseeing molecular testing quality
Related standards
- ISO 15189 (Medical laboratories - Requirements for quality and competence)
- ISO 15190 (Medical laboratories - Requirements for safety)
- Other parts of the ISO 20166 series addressing FFPE pre‑analytics for different analytes
Keywords: ISO 20166-3, FFPE, isolated DNA, pre‑analytical, pre‑examination, molecular diagnostics, DNA integrity, formalin fixation, sample handling.