ISO/TS 7552-3:2024

Overview

ISO/TS 7552-3:2024 - "Molecular in vitro diagnostic examinations - Specifications for pre-examination processes for circulating tumour cells (CTCs) in venous whole blood - Part 3: Preparations for analytical CTC staining" - is a Technical Specification that standardizes the pre-analytical steps needed to obtain reliable CTC staining results from venous whole blood. It covers handling, storage, CTC enrichment, preparation for staining, and documentation during the pre-examination (pre-analytical) phase for molecular in vitro diagnostic examinations, including laboratory developed tests (LDTs). This document supports consistent liquid biopsy workflows and improves comparability of CTC-based assays.

Key topics and requirements

• Specimen collection outside the laboratory
  • Guidance on donor/patient information, venipuncture procedures, selection of appropriate blood collection tubes (with or without stabilizers), and avoidance of backflow.
• Storage and transport
  • Requirements and recommendations for transport conditions, including different handling for tubes with stabilizers versus conventional tubes.
• Specimen reception and storage inside the laboratory
  • Procedures for logging, acceptance criteria, and short-term storage prior to processing.
• CTC enrichment methods
  • Requirements for using commercial CTC enrichment systems and for validating laboratory-developed enrichment procedures; attention to methods based on biological (surface markers) or physical (size, density) properties.
• Preparation for CTC staining
  • Standardized pre-treatment steps for various staining modalities (antibody-based immunocytochemistry, colour stains, in situ techniques) and handling of enriched CTCs (on-slide vs suspension preparations).
• Quality control and documentation
  • Criteria for assessing enriched CTC quality, storage of enriched samples, and required documentation to support traceability and reproducibility.
• Scope limits
  • Does not cover viable CTC cryopreservation/culturing or dedicated genomic DNA/RNA stabilization (see related parts of ISO 7552).

Applications and who should use it

• Medical laboratories performing molecular in vitro diagnostics and CTC analyses
• Developers and manufacturers of in vitro diagnostic (IVD) devices and CTC enrichment systems
• Biobanks, research institutions, and commercial organizations conducting liquid biopsy research
• Regulatory authorities and laboratory customers seeking standardized pre-analytical procedures
• Clinical and translational researchers implementing CTC staining workflows to improve diagnostic accuracy, therapeutic monitoring, and biomarker development

Related standards

• ISO 7552-1 and ISO 7552-2 - complementary parts addressing CTC genomic DNA and RNA stabilization
• ISO 15189 - medical laboratory quality and competence
• ISO 15190 - laboratory safety

Practical adoption of ISO/TS 7552-3:2024 helps reduce pre-analytical variability in CTC workflows, supports reliable CTC staining for diagnostics and research, and strengthens confidence in liquid biopsy results.