Endothelial cells in peripheral blood of healthy subjects and patients with metastatic carcinomas

Background: A lack of standardized assays and consensus of cell definition has lead to a wide variation in the reported range of circulating endothelial cells (CECs). Methods: An automated rare cell analysis system was used to enumerate nucleated, CD146 + /CD105 + /CD45 − CECs in 4 mL of blood. Results: Recoveries of spiked HUVECs were linear over a range of 0–1,241 cells ( R 2 ≥ 0.99) with recoveries of ≥70% at each spike level. Correlation coefficient values for interoperator variability and duplicate sample variation were ( R 2 = 0.99 and 0.90), respectively. Correlation of CEC counts between tubes 1–2 and 2–3 drawn from the same subject in sequence differed ( R 2 = 0.48 and 0.63, respectively). The normal CEC reference range established in 249 healthy donors was 1–20 CECs/mL blood. CEC counts were significantly higher in the 206 metastatic carcinoma patients ( P < 0.0001). Conclusion: CECs can be accurately and reproducibly enumerated in blood and are elevated in metastatic carcinomas compared with healthy donors. Phlebotomy procedures can affect endothelial cell counts. © 2007 International Society for Analytical Cytology