Related Experiment Video
Updated: Jun 4, 2026
Adaptation of Semiautomated Circulating Tumor Cell (CTC) Assays for Clinical and Preclinical Research Applications
Published on: February 28, 2014
External quality assurance of circulating tumor cell enumeration using the CellSearch(®) system: a feasibility study
Jaco Kraan1, Stefan Sleijfer, Michiel H Strijbos
1Department of Medical Oncology, Erasmus Medical Center, Rotterdam, The Netherlands. j.kraan@erasmusmc.nl
Background:
Circulating tumor cells (CTCs) are cells that have detached from solid tumors and entered the blood. CTCs can be detected, among others, by semi-automated immunomagnetic enrichment and image cytometry using CellSearch® (Veridex, Raritan, NJ). We studied the feasibility of external quality assurance (EQA) of the entire CellSearch procedure from blood draw to interpretation of results in multiple laboratories.
Methods:
Blood samples from six cancer patients and controls were distributed to 14 independent laboratories to test between-laboratory, between-assay, and between-instrument variation. Additionally, between-operator variability was assessed through the interpretation of blinded images of all blood samples on a website.
Results:
Shipment and storage of samples had no influence on CTC values. Between-instrument (coefficient of variation (CV) < 12%) and between-assay variation was low (CV ≤ 20%), indicating high reproducibility. However, between-laboratory CV ranged from 45 to 64%. Although inter-operator agreement on image interpretation (Fleiss' κ statistics) ranged from "substantial" to "almost perfect," image interpretation, particularly of samples containing high numbers of apoptotic cells, was the main contributor to between-laboratory variation.
Conclusions:
This multicenter study shows the feasibility of an EQA program for CTC detection in patient samples, and the importance of continuation of such a program for the harmonization of CTC enumeration.
