Blood components: main products and indications

Blood products are divided into two large groups. The first are transfusion components obtained from donor blood by separation methods: red blood cell suspension, platelets, plasma, cryoprecipitate, and granulocytes. The second are plasma-derived medicinal products, also known as plasma-derived preparations: albumin, immunoglobulins, coagulation factors, and prothrombin complexes. This division is important because plasma-derived components are used as immediate supportive therapy, while plasma-derived preparations are produced industrially and used as full-fledged medications. [1]

Blood components are used to correct three main problems: oxygen-transport deficiency in anemia, platelet deficiency or dysfunction in bleeding and bleeding prevention, and coagulation factor deficiency, which requires plasma or cryoprecipitate. Plasma products, on the other hand, address specific medical needs: for example, immunoglobulin for replacement therapy in primary immunodeficiencies, coagulation factor concentrates in hemophilia, and albumin for specific indications. [2]

The safety of these products is ensured at all stages—from donor selection and laboratory screening to technological procedures for disinfection and pathogen reduction. International standards require mandatory testing of each donation for human immunodeficiency virus, hepatitis B virus, hepatitis C virus, and syphilis, as well as a strict quality control system. Additionally, countries may introduce expanded test panels and precautions depending on the epidemiological situation. [3]

It's important for patients and physicians to remember that transfusion is a therapy with proven benefits, but not without risks. Therefore, the concept of "patient blood management" is currently in effect worldwide: first, maximize preventive measures and alternatives, and only after these options have been exhausted, prescribe transfusions based on strict indications and thresholds. This approach improves outcomes and saves resources. [4]

Main types of blood components

Red blood cell suspension restores oxygen transport in cases of symptomatic anemia or acute blood loss. Adults are typically transfused one dose at a time, with the effect assessed. One dose typically increases hemoglobin concentration in adults by 10 g/L, but the actual increase depends on body weight, circulating blood volume, and underlying conditions. The decision on further doses is based on clinical and laboratory monitoring. [5]

Platelet components are indicated for the control of bleeding in thrombocytopenia and platelet dysfunction, as well as prophylactically for low platelet counts prior to invasive procedures. The expected increase after a single therapeutic dose in adults averages approximately 15-25 × 10^9 per L within the first hour, but it varies greatly due to consumption, infections, splenomegaly, and immune factors. If "refractory" is suspected, a corrected increase is calculated and antigen-compatible platelets are selected. [6]

Fresh frozen plasma contains a broad spectrum of coagulation factors and is used for massive blood loss, coagulopathy with bleeding, and certain rare factor deficiencies in the absence of specific concentrates. Plasma is not used to increase circulating blood volume; other solutions are intended for this purpose. Cryoprecipitate is rich in fibrinogen and coagulation factors and is prescribed for decreased fibrinogen and hypofibrinogenemia, including those associated with massive bleeding. [7]

Granulocyte transfusions are used extremely rarely, for life-saving indications in cases of severe neutropenia with life-threatening infections, when antibacterial therapy is ineffective. In general practice, their role is limited due to the risks and logistical difficulties involved. The decision is made by a multidisciplinary team. [8]

Plasma-derived medicinal products

Albumin, immunoglobulins, coagulation factor concentrates, and complex preparations are produced industrially by plasma fractionation with multi-stage inactivation and removal of viruses. The process flow charts include heating, solvent and detergent treatment, low or high acidity, chromatography, nanofiltration, and other steps. The combination of orthogonal steps provides a net reduction in viral load by several logarithms. [9]

The World Health Organization recommends that countries develop secure supply chains for plasma-based medicines, adhering to quality standards, pharmacovigilance, and traceability of raw materials. For resource-limited countries, strategies have been developed to increase the procurement of high-quality plasma and organize contractual fractionation. This increases the availability of life-saving medications while maintaining high levels of safety. [10]

Regulators regularly update requirements for the collection, processing, and quality control of plasma products, including confirmation of the effectiveness of the inactivation steps for unenclosed and enclosed viruses, assessment of the removal of potential pathogens, and testing of residual reagents. The manufacturer is required to demonstrate reproducibility and consistency of virus safety at the level of a specific product line. [11]

Epidemiological risks are also assessed for production processes. For some arboviruses, such as Zika, the fractionation and inactivation process steps are considered sufficient to ensure the safety of finished products, so specific measures typical for blood and its components may not be required. Final decisions are made by regulators, taking into account the current epidemiological situation. [12]

Selection and Compatibility: How to Ensure Accuracy and Safety

Compatibility of the A, B, O, and Rh D blood types is a basic requirement for transfusion. Before each transfusion, the patient's blood type is determined, irregular antibody screening is performed, and a cross-matching test is performed with the component. In emergency situations, the temporary use of blood type O red blood cells with a negative Rh D antigen is permitted, but components that are fully compatible with the patient are switched to as soon as possible. [13]

Leukocyte filtration prior to storage reduces the risk of febrile non-hemolytic reactions, sensitization to leukocyte antigens, and cytomegalovirus transmission. In many countries, such components have become standard. In certain clinical situations, such as in newborns, pregnant women, and during intrauterine transfusions, components from donors without antibodies to cytomegalovirus are additionally used. [14]

Irradiation of cellular components prevents a serious complication—graft-versus-host disease. Irradiated red blood cells and platelets are prescribed to patients with severe immunodeficiency, during transplantation, intrauterine transfusions, and for other indications according to specialized guidelines. [15]

For platelets, unlike erythrocytes, compatibility with the A, B, and O system is more important for efficacy than for safety. If it is impossible to find a dose identical to the A, B, and O system, the least incompatible options are selected and the clinical response and growth rate are assessed. In cases of immune refractoriness, selection based on human leukocyte complex antigens is used. [16]

When to transfuse: thresholds and dosages

Current guidelines support a "restrictive" strategy for red blood cells: in hemodynamically stable adult hospitalized patients, transfusion is considered at hemoglobin concentrations below 70 g/L, taking into account clinical presentation, oxygen saturation, and comorbidities. In certain groups, the threshold may be higher for clinical reasons. This approach does not worsen outcomes and reduces the volume of blood transfused. [17]

For platelets, benchmarks are established: in asymptomatic thrombocytopenia due to hematopoietic suppression, prophylactic transfusions are often initiated at a level of 10 × 10^9 per liter, and before invasive interventions, at higher thresholds depending on the risk of bleeding and the specific procedure. For neurosurgery and central nervous system trauma, target values are significantly higher. The decision is always individualized. [18]

Plasma is considered in cases of coagulopathy with bleeding or before an urgent invasive procedure in a patient with obvious laboratory evidence of a coagulation disorder when there is no time for a specific concentrate. Plasma is not used as a volume replacement. Cryoprecipitate is indicated when fibrinogen levels drop, typically below 1.5-2.0 g/L, to bring levels to safe levels. [19]

A single dose has a predictable, but variable, effect. A single dose of red blood cells in an adult increases hemoglobin by approximately 10 g/L. A single therapeutic dose of platelets often produces an increase of 15-25 × 10^9 per L after 10-60 minutes. A typical pool of cryoprecipitate can increase fibrinogen concentration by 0.5-1.0 g/L, especially if blood loss is stabilized. Repeated testing is always necessary after transfusion. [20]

Storage, pathogen reduction and infection risk control

Storage periods and conditions vary: red blood cells are typically stored at temperatures ranging from 1 to 6 degrees Celsius for up to 42 days, depending on the solution; platelets are stored at room temperature with constant agitation for up to 5-7 days when using bacterial risk control strategies; plasma and cryoprecipitate are stored frozen, with subsequent time restrictions after thawing. These parameters are regulated by specialized guidelines and must be strictly adhered to. [21]

For platelets, bacterial contamination remains the most common infectious risk. To reduce this risk, initial and repeat testing, as well as pathogen reduction technologies based on photochemical processing, are used. Despite these measures, clinicians should remain alert for signs of sepsis in recipients and follow adverse reaction reporting algorithms. [22]

Pathogen reduction and disinfection technologies include photochemical treatment of platelets and plasma, solvent-detergent methods for plasma disinfection, and heating and nanofiltration in the production of plasma-derived products. The combination of independent methods ensures high viral safety, as confirmed by regulatory requirements and validation studies. [23]

Donor screening is the foundation of safety. Laboratory testing of every donation for human immunodeficiency virus, hepatitis B virus, hepatitis C virus, and syphilis is mandatory. Depending on the country and risk, additional tests and measures are implemented, as well as external laboratory quality assessment programs. Blood and components are approved for use only if these conditions are met. [24]

Adverse reactions and their prevention

The most common non-infectious reactions are febrile non-hemolytic reactions and allergic manifestations. The risk of febrile reactions is significantly reduced by leukofiltration prior to storage. Allergic reactions are generally mild and are treated with antihistamines; however, in the event of anaphylaxis, the transfusion is immediately discontinued and emergency treatment is administered. [25]

Transfusion volume overload is a leading cause of severe outcomes. The current definition includes acute or worsening respiratory distress and signs of overload within 12 hours of transfusion. Prevention involves careful assessment of volume and flow rate; vulnerable patients receive small transfusions with close monitoring. [26]

Transfusion-associated acute lung injury (TALI) is characterized by sudden respiratory failure within 6 hours of transfusion in the absence of alternative causes. A current consensus definition distinguishes between cases with and without risk factors for acute respiratory distress syndrome, which helps standardize diagnostics in hemovigilance. Prevention includes donor selection strategies and minimizing plasma components from donors with certain antibodies. [27]

Platelet transfusion-associated sepsis, although rare with current control strategies, remains clinically significant. Monitoring of temperature, blood pressure, and patient status during and after transfusion is essential, and if infection is suspected, immediate notification to the blood service and initiation of therapy are necessary. These measures reduce the severity of outcomes. [28]

Practical tables

Table 1. Classification of blood products and main indications

Group	Examples	Key clinical challenges
Components for transfusion	Red blood cells, platelets, fresh frozen plasma, cryoprecipitate, granulocytes	Correction of anemia, thrombocytopenia, coagulopathy, massive bleeding
Plasma-derived preparations	Albumin, immunoglobulins, coagulation factors, prothrombin complex	Replacement therapy for immunodeficiencies and coagulopathies, specialized indications

Table 2. Storage conditions and typical expiration dates

Component	Conditions	Typical term
Red blood cells	From 1 to 6 degrees	Up to 42 days depending on the solution
Platelets	Room temperature with agitation	Usually up to 5-7 days with bacterial control measures
Plasma	Frozen, then time limited after defrosting	Up to 1 year if frozen, see local regulations
Cryoprecipitate	Frozen	Up to 1 year, limited use after defrosting
Granulocytes	Short-term storage, usually transfusion of "fresh" doses	For urgent indications

Table 3. Threshold values and doses by prescription

Situation	Landmark for appointment	Typical dose and expected effect
Erythrocytes at steady state	Hemoglobin below 70 g/l taking into account the clinical picture	1 dose with control; expected increase ≈ 10 g/l
Prevention of bleeding in case of hematopoiesis suppression	Platelets at 10 × 10^9 per l	1 dose; the increase in an adult is often 15-25 × 10^9 per l
Before an invasive procedure	Individually based on the risk of the procedure	Dose of platelets or plasma as indicated
Hypofibrinogenemia	Fibrinogen below 1.5-2.0 g/l	Cryoprecipitate; expected increase 0.5-1.0 g/L

Table 4. Security methods

Method	Purpose	Where it is applied
Screening of each donation for human immunodeficiency virus, hepatitis B virus, hepatitis C virus and syphilis	Prevention of infection transmission	All donations
Leukofiltration before storage	Reduction of febrile reactions, sensitization, and risk of cytomegalovirus transmission	Red blood cells, platelets
Irradiation	Prevention of graft-versus-host disease	Cellular components in vulnerable groups
Pathogen reduction of platelets and plasma	Reduced risk of bacterial contamination and some viruses	Platelets, plasma

Table 5. Compatibility of the A, B, O and Rh D systems for erythrocytes
(generally; the final decision is based on the results of tests and cross-matching)

Recipient	Preferred donor
Blood group A, Rh D positive	Red blood cells of group A, Rh D positive
Blood group A, Rh D negative	Red blood cells of type A, negative for Rh factor D
Blood group B, Rh D positive	Red blood cells of group B, Rh D positive
Blood group B, Rh D negative	Red blood cells of group B, negative for Rh factor D
Group AB, any Rh factor D	Red blood cells of group AB corresponding to Rh factor D
Blood group O, Rh D negative	Red blood cells of type O, negative for Rh factor D

Table 6. Common adverse reactions and how to prevent them

Reaction	Key Features	Prevention
Febrile non-hemolytic	Chills, fever without hemolysis	Leukofiltration, careful selection
Allergic	Skin itching, urticaria, sometimes anaphylaxis	Premedication in susceptible individuals, discontinue in case of severe reaction
Circulatory volume overload	Shortness of breath, wheezing, hypertension for 12 hours	Small volumes, slow speed, monitoring
Transfusion-associated acute lung injury	Acute respiratory failure within 6 hours	Donor selection strategies, reduction of plasma exposure
Post-platelet sepsis	Fever, hypotension, signs of shock	Pathogen reduction, bacterial control, active monitoring

Patient-oriented tactics and special situations

The concept of "patient-centered blood management" combines optimization of erythropoiesis, minimization of blood loss, and rational use of components. This includes early diagnosis and treatment of anemia before surgery, thoughtful blood conservation techniques during interventions, careful adherence to transfusion thresholds, and shared decision-making with the patient. This approach reduces the risk of complications and increases treatment satisfaction. [29]

In neonates and children, transfusion thresholds and target values differ from those in adults, and safety is ensured by additional measures, including the selection of components without antibodies to cytomegalovirus and with leukofiltration, and, if necessary, irradiation. Indications and thresholds depend on postnatal age, the presence of respiratory support, and comorbid conditions. [30]

In obstetrics, oncohematology, and intensive care, individualization is essential: blood loss dynamics, coagulation profile, and clinical presentation are considered, targeted components are used, and excessive transfusions are avoided. In cases of immune refractoriness to platelets, specialized antigen selection and efficacy monitoring based on adjusted platelet increment are indicated. [31]

Regulatory requirements for the procurement and use of blood components and plasma products are regularly updated. In Europe, a unified technical "Blood Guide" of the Council of Europe is in effect, as is the current regulation on substances of human origin, which strengthens uniform quality and safety standards. In the United States and Canada, guidelines from professional societies and federal regulations are used as a guide. [32]

Brief conclusions

1. Blood products are both a "fire brigade" for acute support and complete plasma-derived medicinal products for specific diagnoses; their safety is ensured by a multi-level control system. [33]
2. The decision to transfuse is made based on clinical and threshold criteria, with priority given to a restrictive strategy and re-evaluation of the effect after each dose. [34]
3. Prevention of complications begins before transfusion: correct choice of component, compatibility, leukofiltration, pathogen reduction, irradiation according to indications and vigilant monitoring. [35]