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Blood donation glossary

Plain-English definitions of the words you will hear at a blood bank or on a camp day — component, crossmatch, deferral, apheresis, TTI screening, lookback, and the rest.

Blood banking has its own vocabulary, most of it borrowed from laboratory medicine, and it gets used around donors and families who have never heard it before. This page defines the terms you are most likely to encounter, in the order of how often you will hear them rather than alphabetically.

Whole blood

Blood as it is collected from a donor, before anything is done to it. A standard whole-blood donation is a single unit of around 450 millilitres.

Most whole blood is not transfused as whole blood. It is separated into components within hours of collection, because different patients need different parts of it and each part keeps best under different conditions. When whole blood is transfused, it must be the patient's own group — the more permissive compatibility rules people remember apply to separated red cells, not to whole blood.

Component

One of the products separated out of a unit of whole blood. The four you will hear named:

• Packed red cells, sometimes PRBC — the oxygen-carrying part, used for blood

loss and severe anaemia. Refrigerated, and the longest-lasting of the cellular products at about 35 days.

• Platelets — the fragments that make blood clot. Stored at room temperature

under continuous gentle agitation, and good for only about 5 days, which is why platelets are perpetually in short supply.

• Fresh frozen plasma, or FFP — the liquid part, carrying clotting factors.

Deep frozen, and keeps about a year.

• Cryoprecipitate — a concentrate separated from thawed plasma, used for

specific clotting problems. Also deep frozen, also about a year.

A single donation can therefore help more than one patient, which is the honest answer to "does one unit really matter".

Unit, and bag

A unit is one donation's worth of a component. A bag is the physical container it is in. People use the words interchangeably, and a request for "two units" means two bags of whatever component was asked for.

Component separation

The process of spinning collected whole blood in a centrifuge so that it settles into layers by density, then drawing the layers off into separate bags. It happens at the blood bank, not at the camp, and it is why the unit you donate in the morning is not available to a patient in the afternoon.

Apheresis

A collection method where blood is drawn from a donor, passed through a machine that removes only one component, and the rest returned to the donor in the same sitting. It takes longer than a whole-blood donation and needs specific equipment.

Its main use is platelets. An apheresis platelet donation — you may hear it called SDP, for single donor platelets — yields enough platelets for a patient from one donor, rather than pooling the small platelet layers from several whole-blood donations. For a patient needing platelets repeatedly, fewer donors means less exposure.

Because the red cells go back to the donor, the interval before a platelet donor can give again is much shorter than after a whole-blood donation. The blood bank sets it.

Screening, and deferral

Screening is the medical assessment a donor goes through before collection: a short history, pulse and blood pressure, and a haemoglobin check. It protects the donor as much as the recipient.

Deferral is the outcome when someone should not donate. A temporary deferral has an end date — recent illness, a recent vaccination, a course of antibiotics, a tattoo, a recent surgery. A permanent deferral means this person should not donate again.

Being deferred is routine. It happens to people every day at every blood bank, and it is not a statement about anyone's health in general. The only person who can decide it is the doctor doing the screening: an online questionnaire — on Raktify or anywhere else — is a filter to save you a wasted trip, never a clearance.

Minimum interval between donations

The waiting period a donor must observe after donating before giving again, so that the body has replaced what was taken. It differs by what was donated and, for whole blood, between men and women.

Raktify tracks it so that you are not asked for blood when you are not yet eligible, and the specific figures belong to the blood bank's own protocol rather than to a web page.

TTI screening

Testing for transfusion-transmissible infections. Every unit collected in India must be tested before release, and the mandatory panel covers HIV, hepatitis B, hepatitis C, syphilis and malaria.

A unit that tests reactive is discarded and the donor is informed and counselled privately. This is one of the strongest arguments for donating through a licensed blood bank: the testing is not optional and not skipped.

Reactive

The laboratory's word for a test that has come back positive, used in preference to "positive" because a screening test needs confirmation. A reactive screening result is a reason to discard the unit and to talk to the donor; it is not by itself a diagnosis.

Crossmatch

A laboratory test that mixes a sample of the specific patient's blood with the specific unit intended for them, to confirm they are compatible in practice and not just on paper. Required for red cells and whole blood.

Crossmatching is why a hospital cannot simply be handed a compatible-looking unit and why "we have your group in stock" is not the last step. Platelets and plasma are handled differently.

Group, and verified group

Your ABO group and Rh type — A, B, AB or O, positive or negative. Established by testing a sample, which is something only a laboratory can do.

Raktify distinguishes a self-reported group, which you type in and which is shown marked unverified, from a verified group recorded by a licensed blood bank. Only the verified one is used to match you to a patient. A group remembered from an old report is wrong often enough that trusting it would eventually send a family the wrong donor.

Lookback

The process of tracing, after the fact, where every unit from a particular donor went — usually because that donor was later found to have an infection that was not detectable when they donated.

Lookback is the reason blood banking is so insistent about records. It only works if the chain from donor to unit to patient is complete and cannot be quietly altered after the fact. Raktify's audit log is append-only for the same reason: no user, administrator or engineer can edit or delete an entry.

Chain of custody

The record of where a specific bag has been: issued by the blood bank against a specific request, received by the hospital, then transfused, returned or written off. Each step is recorded with who did it and when.

Camp

A blood donation drive held away from the blood bank's own premises — in a college, an office, a housing society, a temple. The blood bank brings staff and equipment; the organiser provides the venue, the people and the logistics.

The organiser never handles blood or makes medical decisions. Collected units go back to the blood bank's licensed storage for separation and testing like any other donation.

Replacement donation

The practice of asking a patient's family to bring donors to offset the units the patient uses. It is widespread in India and it is not the same as voluntary donation: the donor is under family pressure, which is exactly the circumstance in which someone hides a reason they should not be donating.

Voluntary non-remunerated donation — no payment, no family obligation — is what blood services worldwide work towards, and it is the only kind Raktify supports.

Voluntary non-remunerated donor

Someone who donates of their own free will, for no payment and under no pressure. In India, paying a blood donor is illegal. The hospital charge a patient's family sees covers collection, testing and processing, not the blood.