Practical considerations- Number of cells

If very little sample is provided (e.g. < 5 mL blood or bone marrow) or the white blood cell count is very low, there is unlikely to be sufficient RNA to extract for testing. This may be a particular issue when testing samples from the few patients with refractory CML who undergo allogeneic stem cell transplantation, as there may be insufficient sample during induction therapy and in the early stages of engraftment and immune reconstitution. Experts recommend that at least 10 million white blood cells are needed for testing with high sensitivity.