The PDQ editorial boards use a ranking system of levels of evidence to help the reader judge the strength of evidence linked to the reported results of a therapeutic strategy. For any given therapy, results of prevention and treatment studies can be ranked on each of the following two scales:
Strength of the study design.
Strength of the endpoints.
Together, the two rankings provide a measure of the overall level of evidence. Screening studies are ranked on strength of study design alone...
antibodies: Proteins made by your body that fight off foreign substances.
antigen: A foreign substance, such as a bacteria, virus, or tissue, that does not come from your body.
apheresis: A process in which whole blood is drawn from a donor, the stem cells are then harvested, and the other blood products are returned to the donor.
autologous: Stem cell transplantation using your own stem cells.
bone marrow: The spongy part of some bones, where blood cells develop from immature marrow cells called stem cells.
bone marrow transplant (BMT): A transplant containing all three types of blood cells that develop in the bone marrow: red cells, white cells, and platelets. (Stem cell transplants only use the immature stem cells from the circulating blood.)
cord blood transplant: Stem cell transplant using cells collected from the umbilical cord and placenta of healthy newborns.
conditioning (cytotoxic or myeloablative) treatment: High-dose chemotherapy and/or radiation given before a stem cell transplant.
embryonic stem cells: Immature cells from umbilical cord blood that can develop into many types of cells, including blood cells.
granulocyte colony-stimulating factor drugs: Growth factor medicines given to draw stem cells from the bone marrow into the bloodstream.
graft (autograft or allograft): The new blood-producing cells that develop after a successful stem cell transplant.
graft-versus-host disease: A condition in which donor cells think the recipient's cells are foreign and attack them.
graft-versus-tumor effect (GVT): The good response that happens when the donor cells attack any of the recipient's cancer cells that may remain after chemotherapy.
growth factor: Medicines that boost the numbers of infection-fighting white blood cells.
harvesting: The process of collecting stem cells.
hematopoietic stem cells: Immature blood cells or blood-forming stem cells.
hematopoiesis: The process by which the body makes red blood cells.
human leukocyte antigens (HLA): Proteins found on the surface of white blood cells and tissues. A tissue-typing test shows how many HLA matches the recipient has in common with a donor.
immune system: A network of cells, tissues, and organs that protects your body from disease and infection.
indwelling catheter (central line): A tube surgically placed in your chest near your neck through which to give chemotherapy and receive your stem cell infusion. It may also be used to draw blood. This type of catheter is also known as a "port."
infusion: Delivery of liquid medicine or treatment through a vein.
matched unrelated donor (MUD): A donor who is not a blood relative, but who has a complete HLA match to the patient. These donors are often found through bone marrow registries.