Components of Donated Blood Products

What happens to donated blood after it leaves the donor?

Blood is a complex tissue. Each part has a different job, a different shelf life, and a different storage temperature. Modern transfusion medicine takes advantage of those differences. Instead of giving a patient a whole bag of blood when they only need one part of it, blood services separate each donation into components and match each component to the patient who needs it. This approach is called component therapy, and it is the reason a single donation can help several different patients [6,7].

Donated blood reaches the blood bank in one of two ways: as a whole blood donation that is processed afterwards, or through apheresis, where the desired component is collected directly.

Whole Blood Donation and Blood Component Separation

A standard whole blood donation collects about 450–500 mL into a bag containing anticoagulant and preservative. Inside the blood bank, the bag goes through a high-speed centrifuge. Density does the work: cells settle, plasma rises, and three layers form.

1. Plasma sits on top — a straw-colored liquid, the least dense component. It is expressed off and rapidly frozen to make FFP.
2. Buffy coat is the thin whitish middle layer. It contains most of the white cells and platelets.
3. Packed red blood cells (PRBC) sit at the bottom. An additive solution is mixed in to extend their shelf life.

A sterile, closed-system extractor moves each layer into its own bag. Buffy coats from four to six donors can be pooled and processed into one therapeutic dose of platelet concentrate.

Apheresis: collecting one component directly

The word apheresis comes from the Greek for "to take away." A donor's blood passes through an automated cell separator that pulls out one component (platelets, plasma, or red cells) and returns everything else to the donor. The donation takes longer, but the patient ends up exposed to fewer donors. That single-donor exposure is the key clinical advantage: a patient who receives one apheresis platelet unit is exposed to one person's antigens and infectious-disease risk, instead of four to six.

Apheresis blood product	Key Benefit
Apheresis Platelets	One donation = one full adult therapeutic dose (equivalent to 4–6 pooled whole-blood platelets). Reduces donor exposure.
Apheresis Plasma	Larger volumes per donation; donors can give more often.
Double Red Cell Apheresis	Two PRBC units from one donor. Highly efficient.

The major blood components

Whole Blood

Whole blood contains everything a donor gave: red cells, plasma, platelets, and white cells. Historically it was the standard transfusion product, but component therapy replaced it for almost all routine indications. Whole blood has made a real comeback in one setting: massive, life-threatening hemorrhage, especially in trauma and military medicine [5].

Storage and shelf life. Stored at 1–6°C. Shelf life depends on the anticoagulant: 21 days in CPD, up to 35 days in CPDA-1.

When it's used. Activation of a Massive Transfusion Protocol (MTP) for severe trauma, major obstetric hemorrhage, or massive surgical blood loss.

Low-titer group O whole blood (LTOWB)

LTOWB is the version of whole blood now stocked at many civilian trauma centers. It is collected from group O donors who have been screened for low titers of anti-A and anti-B antibodies, which makes it safer to give to patients of any blood group before their type is known. A 2024 meta-analysis of nearly 60,000 trauma patients found LTOWB associated with improved early survival compared with component therapy in some populations, and the multicenter TROOP randomized trial is currently testing this directly [5]. The modern trauma bay does not always reach for separated components first.

Leukodepleted Whole Blood

Leukodepletion means filtering most of the white cells out of a blood product before storage. The standard is fewer than 5 × 10⁶ leukocytes per unit (US AABB) or fewer than 1 × 10⁶ per unit (UK/EU). Removing these cells lowers the rates of:

• febrile non-hemolytic transfusion reactions (FNHTRs),
• TRALI,
• HLA alloimmunization, and
• cytomegalovirus (CMV) transmission, because CMV hides inside donor leukocytes.

In many countries, including the UK, almost all cellular blood products are now leukodepleted by default.

Packed Red Blood Cells (PRBCs)

PRBCs are red cells with most of the plasma removed. They are the workhorse blood product for raising oxygen-carrying capacity.

Storage. 1–6°C. Shelf life is 21 days in CPD, 35 days in CPDA-1, and up to 42 days in additive solutions like AS-1, AS-3, or AS-5.

Volume and effect. A typical adult unit is about 250–350 mL and raises hemoglobin by roughly 1 g/dL.

When PRBCs are used.

• Symptomatic or chronic anemia (e.g., chemotherapy-induced, kidney disease, thalassemia, sickle cell disease)
• Acute blood loss after the patient has been resuscitated
• Surgery with significant blood loss

The 2023 AABB international red cell transfusion guideline reaffirmed a restrictive threshold of 7 g/dL for most stable adult inpatients, and 7.5 g/dL for cardiac surgery, rather than the older liberal 10 g/dL trigger [1]. Additionally, a threshold of 8 g/dL is recommended for patients undergoing orthopedic surgery or those with preexisting cardiovascular disease [1].

Fresh Frozen Plasma (FFP)

FFP is the liquid portion of blood that has been frozen quickly to keep its clotting factors active. To be labeled FFP, the plasma must be placed in the freezer at −18°C or colder within 8 hours of collection under FDA/AABB standards. (If freezing happens between 8 and 24 hours, the unit is labeled PF24 instead — Factor V and VIII activity is slightly lower but the product is still clinically useful.)

Storage and shelf life. −18°C or colder; up to 12 months. Once thawed, FFP must be kept at 1–6°C and used within 24 hours.

Volume. About 200–250 mL per whole-blood-derived unit.

When FFP is used.

• Multiple coagulation factor deficiencies in a bleeding patient
• Liver disease with active bleeding
• Disseminated intravascular coagulation (DIC) with bleeding
• Massive transfusion (as part of a 1:1:1 ratio)
• Plasma exchange in thrombotic thrombocytopenic purpura (TTP)

Platelet Concentrates

Platelets stop bleeding by forming the initial plug at sites of vascular injury. Patients with low counts (thrombocytopenia) or dysfunctional platelets may need a transfusion to either prevent or treat bleeding.

Storage. 20–24°C with continuous gentle agitation; shelf life 5 days (sometimes 7 days with secondary bacterial testing). Pooled units have a shorter open-system limit.

Volume and effect. A pooled or apheresis adult dose is about 250–350 mL and typically raises the platelet count by 30–60 × 10⁹/L.

Updated thresholds — 2025 AABB/ICTMG guidelines [2].

Clinical Situation	Suggested Transfusion Threshold
Non-bleeding, hypoproliferative (Chemo, Allo-SCT)	< 10 × 10⁹/L
Central venous catheter placement (compressible)	< 10 × 10⁹/L
Lumbar puncture	< 20 × 10⁹/L
Interventional radiology (Low-risk)	< 20 × 10⁹/L
Neonatal consumptive thrombocytopenia (non-bleeding)	< 25 × 10⁹/L
Interventional radiology (High-risk)	< 50 × 10⁹/L
Major non-neuraxial surgery	< 50 × 10⁹/L

The same guideline recommends against prophylactic platelet transfusion in autologous stem cell transplant or aplastic anemia patients who are not bleeding, and against platelets in dengue without major bleeding [2].

When platelets are contraindicated or used cautiously. Immune thrombocytopenia (ITP), heparin-induced thrombocytopenia (HIT), TTP, and hemolytic uremic syndrome (HUS) — unless there is life-threatening bleeding. Giving platelets in these conditions can fuel ongoing thrombosis or accelerate destruction.

Cold-stored platelets — the new option

In June 2023 the U.S. FDA issued guidance allowing apheresis platelets to be stored at 1–6°C for up to 14 days for the treatment of active bleeding when conventional room-temperature platelets are unavailable or impractical [4]. The 34th edition of the AABB Standards, effective April 2024, incorporates this change. Cold-stored platelets do not need agitation, have lower bacterial contamination risk, and form clots faster — but they are cleared from circulation more quickly, so they are not used for prophylaxis.

Recent data, including the 2024 CriSP-HS trial, demonstrated that cold-stored platelets can be administered significantly faster to trauma patients without compromising safety, highlighting their logistical advantage [13].

Cryoprecipitate

Cryoprecipitate is what's left when FFP is thawed slowly at 1–6°C: a small, concentrated white precipitate rich in fibrinogen, factor VIII, factor XIII, and von Willebrand factor. The supernatant (cryo-poor plasma) is removed, the precipitate is resuspended in a small volume, and the product is rapidly refrozen.

Storage. Below −18°C; shelf life 12 months. Once thawed, must be used within 4–6 hours.

Volume. About 10–15 mL per unit; typically pooled.

When cryoprecipitate is used.

• Acquired hypofibrinogenemia (e.g., DIC, massive transfusion, obstetric hemorrhage)
• Congenital fibrinogen disorders and dysfibrinogenemia
• Factor XIII deficiency
• von Willebrand disease and hemophilia A — historically, but now superseded by specific factor concentrates wherever available

The 2023 CRYOSTAT-2 trial tested empirical early high-dose cryoprecipitate in trauma hemorrhage and did not show a mortality benefit, which has shaped current MTP design [9]. Consequently, modern MTP design favors goal-directed therapy using viscoelastic assays (like TEG or ROTEM) to deliver targeted hemostatic interventions only when hypofibrinogenemia is actively documented [10].

Plasma derivatives and other blood products

The components above come from a blood bank's separation lab. The blood products in this section come from large-scale plasma fractionation of pooled donor plasma at pharmaceutical facilities. Treating them as a separate category helps avoid confusion.

• Human albumin (4.5% and 20%) — Plasma volume expander; used in plasmapheresis fluid replacement, severe hypoalbuminemia (especially with nephrotic syndrome or liver failure), and selected resuscitation indications.
• Specific immunoglobulins — Concentrated antibodies from donors with high titers (e.g., anti-hepatitis B, anti-tetanus, anti-Rh(D)). Used for post-exposure prophylaxis and, in the case of anti-D, to prevent hemolytic disease of the newborn.
• Pooled (intravenous) immunoglobulin (IVIG) — Used in primary and secondary immunodeficiency, autoimmune conditions including immune thrombocytopenia (ITP), and some neurological diseases.
• Factor VIII concentrate (recombinant or plasma-derived) — Hemophilia A.
• Factor IX concentrate / 4F-PCC — Hemophilia B; warfarin reversal in major bleeding.
• Protein C concentrate — Severe sepsis with DIC and protein C depletion; congenital protein C deficiency.
• Granulocyte concentrates — Collected from G-CSF–stimulated healthy donors. Used rarely, in severe neutropenia with documented infection unresponsive to antibiotics and antifungals.

A growing number of services also produce pathogen-reduced plasma and platelets using systems like INTERCEPT or Mirasol, which inactivate residual leukocytes and most viruses, bacteria, and parasites. Pathogen reduction can substitute for irradiation and eliminates the need for CMV-seronegative testing in many settings [11].

Specialized modifications for unique patient needs

Some patients need standard components modified to make them safer.

Irradiated blood products

Gamma or X-ray irradiation inactivates donor T-lymphocytes so they cannot divide. This prevents transfusion-associated graft-versus-host disease (TA-GVHD), a rare but nearly always fatal complication (mortality > 90%) in which donor T-cells attack the recipient.

Storage. Same as the un-irradiated component; shelf life is the original expiry date or 28 days from irradiation, whichever is sooner. Irradiation accelerates potassium leakage from red cells.

Who needs it.

• Recipients of blood from first- or second-degree relatives
• Patients on highly immunosuppressive therapy (e.g., bone marrow transplant, fludarabine-based regimens, congenital cellular immune deficiency)
• Intrauterine transfusions and neonatal exchange transfusions
• Patients receiving HLA-matched platelets

Washed red blood cells

Washing means rinsing red cells repeatedly with sterile saline to remove plasma proteins, electrolytes, and additives.

Main indication. Patients with selective IgA deficiency and anti-IgA antibodies, who can have anaphylaxis from even tiny amounts of donor IgA. Also useful for severe recurrent allergic reactions not prevented by premedication, and for neonates or patients with renal failure who cannot handle the potassium load of stored red cells.

Shelf life. 24 hours at 1–6°C, because washing breaks the closed system.

Pre-transfusion testing: making sure the unit is safe

Compatibility testing rests on three pillars.

ABO and RhD Typing (Group)

ABO grouping uses two checks that must agree:

• Forward grouping tests the patient's red cells for A and B antigens.
• Reverse grouping tests the patient's plasma for anti-A and anti-B antibodies.

RhD typing checks for the D antigen on red cells. RhD-negative patients should generally receive RhD-negative red cells, particularly women of childbearing age, to prevent anti-D formation and hemolytic disease of the newborn in future pregnancies.

Antibody Screen (Screen)

The antibody screen looks for unexpected (alloantibody) responses in the patient's plasma against red cell antigens other than A and B. These antibodies usually form after pregnancy or previous transfusion. A positive screen triggers antibody identification so that antigen-negative units can be selected, preventing a delayed hemolytic transfusion reaction.

Crossmatch (Compatibility Test)

The crossmatch is the final compatibility check, simulating the transfusion in vitro.

• Major crossmatch mixes recipient plasma with donor red cells. Agglutination or hemolysis means incompatibility.
• Electronic (computer) crossmatch is allowed when the patient has a negative current and historical antibody screen — fast and safe.
• Serological crossmatch is required when antibodies are present, using full incubation and antihuman globulin steps.

Specialized Compatibility Considerations

CMV-safe blood is needed for severely immunocompromised CMV-negative patients (premature neonates, hematopoietic stem cell transplant recipients, some HIV patients). CMV-seronegative units and leukodepleted units are considered equivalent because the virus lives in donor leukocytes.

The 72-hour rule applies if the patient has been transfused or pregnant within the last three months. Their pre-transfusion sample is valid for only 72 hours, because either event can stimulate a new alloantibody that an older sample would miss.

Why this matters clinically

Behind every bag of any blood product is a donor and a series of careful laboratory steps. For a patient with leukemia, a single platelet transfusion can mean another safe day. For a trauma patient hemorrhaging in a rural hospital, a unit of LTOWB can mean reaching definitive care alive. Knowing which blood product fits which clinical situation — and which one does not — is one of the most useful skills a student in hematology can build.

Frequently Asked Questions (FAQs)

What is the difference between a blood product and a blood component?

A blood component is one of the parts separated from a single whole-blood donation: red cells, plasma, platelets, or cryoprecipitate. A blood product is the broader category that also includes plasma derivatives like albumin, immunoglobulins, and factor concentrates that come from large-scale plasma fractionation.

Which blood product is given for symptomatic anemia?

Packed red blood cells (PRBCs). One adult unit raises hemoglobin by about 1 g/dL. Whole blood is reserved for massive hemorrhage where all components are being lost together.

Why is fresh frozen plasma frozen so quickly after donation?

Plasma must be placed in a freezer at −18°C or colder within 8 hours of collection to preserve heat-labile clotting factors V and VIII. If freezing occurs between 8 and 24 hours, the unit is labeled PF24, with slightly reduced labile factor activity but still useful in most plasma indications.

Who needs irradiated blood products?

Patients at risk of TA-GVHD: intrauterine and neonatal exchange transfusion recipients, severely immunocompromised patients (stem cell transplant, congenital immunodeficiency, high-dose chemotherapy), recipients of HLA-matched platelets, and anyone receiving blood from a first- or second-degree relative.

What are cold-stored platelets?

Cold-stored platelets are apheresis platelets kept at 1–6°C for up to 14 days (FDA, 2023) for the treatment of active bleeding when standard room-temperature platelets are unavailable or impractical [4]. They are not used for prophylaxis because they clear quickly from the circulation.

Is FFP still the first choice for warfarin reversal?

No. Current guidelines prefer 4F-PCC for major bleeding on warfarin because it acts faster, requires less volume, and has higher factor concentrations. FFP remains an option only when 4F-PCC is unavailable.

Glossary of Medical Terms

• Alloantibody — Antibody made against red cell antigens from another person, usually after pregnancy or transfusion.
• Apheresis — Donation method in which a machine separates one blood part and returns the rest to the donor.
• Buffy coat — Pale layer between plasma and red cells after centrifugation; rich in white cells and platelets.
• Cold-stored platelets (CSP) — Apheresis platelets stored at 1–6°C for up to 14 days, used for active bleeding.
• Component therapy — Giving the patient only the blood part they need.
• Cryoprecipitate — A frozen plasma fraction rich in fibrinogen, factor VIII, factor XIII, and VWF.
• DIC (Disseminated Intravascular Coagulation) — A condition of widespread inappropriate clotting that depletes clotting factors and causes bleeding.
• FFP (Fresh Frozen Plasma) — Plasma frozen within 8 hours of collection to preserve clotting factors.
• FNHTR (Febrile Non-Hemolytic Transfusion Reaction) — Common, non-life-threatening fever and chills caused by donor leukocyte products or cytokines.
• Leukodepletion — Filtering white cells out of a blood product to lower fever reactions, CMV transmission, and HLA sensitization.
• LTOWB (Low-Titer Group O Whole Blood) — Group O whole blood with low anti-A and anti-B titers, used in early trauma resuscitation.
• Massive Transfusion Protocol (MTP) — Standardized hospital plan delivering balanced (about 1:1:1) red cells, plasma, and platelets in life-threatening bleeding.
• PRBCs (Packed Red Blood Cells) — Concentrated red cells used to raise oxygen-carrying capacity.
• TA-GVHD (Transfusion-Associated Graft-versus-Host Disease) — Rare, almost always fatal reaction prevented by irradiation.
• Thrombocytopenia — Low platelet count.
• TRALI (Transfusion-Related Acute Lung Injury) — Acute non-cardiogenic pulmonary edema within 6 hours of transfusion.
• VWF (von Willebrand Factor) — Plasma protein that helps platelets stick and protects factor VIII.
• 4F-PCC (Four-Factor Prothrombin Complex Concentrate) — Concentrated factors II, VII, IX, X used for rapid warfarin reversal.

Disclaimer: This article is intended for informational purposes only and is specifically targeted towards medical students. It is not intended to be a substitute for informed professional medical advice, diagnosis, or treatment. While the information presented here is derived from credible medical sources and is believed to be accurate and up-to-date, it is not guaranteed to be complete or error-free. See additional information.

References

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