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.