Over 100 years ago, it was discovered that different people have different types of blood. The major types are 'O', 'A', 'B' and 'AB'.
For a blood donation to be helpful to a patient, there has to be a good match between the blood type of the donor and that of the patient receiving the blood. While receiving blood from someone of exactly the same type is fine, some types can happily mix with certain others, while others do not mix well. The common Type O can be given safely to patients with A, B or AB blood. But Type O patients can only receive blood from other Type O people.
Each major blood group is divided into Rh negative or positive types. On average, 45% of the population is Type O, 40% Type A, 10% Type B and 5% Type AB. Check the chart at the left to see where you fit in.
More recently, a number of characteristics, sometimes called markers and antigens, have been found in blood. We inherit these unique characteristics from our parents. Sometimes the process of finding compatible blood for someone with rare markers or a rare blood type is complex and challenging. Fortunately New York Blood Center has a team of world-renowned "match-makers" in our Immunohematology Lab who search for just the right compatible blood for a particular patient in need.
In fact, NYBC has the largest inventory of rare blood types in the U.S. - but we always need more rare blood. Almost everyday we receive a call from a hospital somewhere in the world trying to locate a rare blood type for a specific patient. These precise units are so rare, in fact, that we specially classify them as either "Code 99" or "Code 96" donors. Code 96 donors lack a particular combination of common markers, while Code 99 donors lack a marker nearly all other people have. Giving rare units of blood a special designation makes storage and, more importantly, retrieval of these rare units easier. That's also why we encourage donors to self-identify their ethnicity on our donor registration forms so the screening process for a rare unit of blood likely to be found within a specific ethnic group is streamlined for a patient in need.
CMV (cytomegalovirus) is a common virus found in the environment that can be spread through body fluids including blood transfusions. Many people may have been exposed to CMV, and are therefore CMV Positive, without even knowing it. Infection with CMV is commonly encountered in up to 50 percent of the general population. It is not generally a serious infection except for people who are already in compromised health conditions, newborn babies or pregnant women, in which case the CMV virus could cause birth defects. Doctors therefore seek out known CMV Negative blood for transfusions for newborns or other specific patients where the presence of the CMV virus could cause serious health complications. It's also important to note that unlike blood type, CMV status can change over time. So be sure to check your donor card for your CMV status.