A cancer prognostic test based on just 20 ml of blood is nearly ready for clinical testing by Immunicon Corp., which has developed an "immunomagnetic" technology to find cancer cells circulating in the blood.

Immunicon's magnetic separation device uses colloidal iron, coated with antibodies to the epithelial cell adhesion molecule Ep-CAM, to snag the cells. A magnetic field is then applied to separate the cells from the rest of the blood.