Unit 3: Blood components and quality control
Blood Banking notes · PTU syllabus (BMLS603-18)
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Unit summary
Separating blood into components gives each patient exactly what they need. This unit covers packed, washed and frozen red cells, platelet-rich plasma, platelet concentrates, fresh and fresh frozen plasma, cryoprecipitate, blood substitutes, apheresis and quality control in the blood bank.
After this unit you can
- Prepare red cell components
- Prepare platelet and plasma components
- Describe blood substitutes and apheresis
- Apply quality control in the blood bank
PTU syllabus topics
- Preparation of packed/washed/frozen red cells
- platelet-rich plasma/concentrate/frozen platelets
- fresh plasma/FFP/cryoprecipitate
- blood substitutes
- haemapheresis for leucocytes
- platelets and plasma
- quality control in the blood bank
Packed red cells
2–6 °C, up to 35–42 days
Anaemia, blood loss
Platelet concentrate
20–24 °C with agitation, 5 days
Low platelets, bleeding
Fresh frozen plasma
−30 °C or colder, up to 1 year
Clotting factor deficiency
Cryoprecipitate
−30 °C or colder, up to 1 year
Low fibrinogen, factor VIII
Topic 1
Component preparation: principle
- Whole blood collected in double, triple or quadruple bags is centrifuged; components separate by specific gravity — red cells at the bottom, buffy coat (white cells and platelets) in the middle, plasma on top — and are expressed into satellite bags in a closed system.
- 1Light spin (e.g., 1,500 g for 5–8 minutes)
- 2Express platelet-rich plasma to a satellite bag; red cells remain (add SAGM)
- 3Heavy spin of PRP
- 4Express platelet-poor plasma (freeze as FFP within 6–8 hours)
- 5Leave 50–70 mL plasma with platelets — rest 1 hour, then agitate
Topic 2
Red cell components
Packed red cells
Plasma removed; PCV 65–75% (55–65% with SAGM)
Anaemia; 2–6 °C up to 35–42 days
Washed red cells
Washed with saline to remove plasma
IgA deficiency, repeated allergic reactions; use within 24 hours
Leucoreduced red cells
Filters remove white cells
Prevent febrile reactions, CMV transmission, HLA alloimmunisation
Irradiated red cells
Gamma irradiation
Prevent TA-GvHD in immunocompromised recipients
Frozen red cells
Glycerol cryoprotectant; stored at −65 °C or colder
Rare groups for up to 10 years; deglycerolise before use
- Dose: one unit raises Hb by about 1 g/dL in an adult.
Topic 3
Platelet components
Platelet-rich plasma (PRP)
Intermediate product; platelets in plasma
Used to make concentrates
Random donor platelets (platelet concentrate)
From one whole blood unit; at least 4.5 × 10¹⁰ platelets
20–24 °C with continuous agitation for up to 5 days
Single donor platelets (apheresis)
From one donor; at least 3 × 10¹¹ platelets — equal to 6–8 random units
Same; less donor exposure
Frozen platelets
DMSO cryopreserved
Limited, special uses
- Dose: one random donor unit raises the platelet count by about 5,000–10,000/µL. Platelets are the component most prone to bacterial contamination because they are stored warm.
Topic 4
Plasma components
Fresh plasma
Separated and used quickly
Rarely used now
Fresh frozen plasma (FFP)
Frozen within 6–8 hours at −30 °C or colder; up to 1 year
Multiple factor deficiencies — liver disease, DIC, warfarin reversal, massive transfusion
Cryoprecipitate
FFP thawed slowly at 1–6 °C; cold-insoluble precipitate refrozen
Rich in fibrinogen, factor VIII, vWF, factor XIII, fibronectin — hypofibrinogenaemia, DIC
Cryo-poor plasma
Supernatant after cryo removal
Plasma exchange in TTP; fractionation
- Plasma fractionation (industrial) produces albumin, immunoglobulins and factor concentrates.
Topic 5
Blood substitutes
- Plasma expanders (volume replacement): crystalloids (normal saline, Ringer's lactate) and colloids (albumin, gelatin, starch, dextran) restore volume but do not carry oxygen.
- Oxygen carriers: haemoglobin-based oxygen carriers and perfluorocarbons remain experimental or restricted. Patient blood management (treating anaemia, cell salvage, tranexamic acid) reduces transfusion needs.
Topic 6
Haemapheresis
- Apheresis: blood is drawn into a cell separator, the desired component removed and the rest returned to the donor or patient.
- Plateletpheresis
- Single donor platelets
- Leucapheresis
- Granulocytes; stem cells (peripheral blood stem cell collection)
- Plasmapheresis
- Plasma for fractionation
- Therapeutic apheresis
- Plasma exchange (TTP, Guillain–Barré, myasthenia), leucodepletion in hyperleucocytosis, red cell exchange in sickle crisis
- Complications: citrate toxicity (tingling — low ionised calcium), vasovagal reactions, vascular access problems.
Topic 7
Quality control in the blood bank
Packed red cells
PCV 70 ± 5% (55–65% with SAGM)
1% of units or at least 4 per month
Random donor platelets
At least 4.5 × 10¹⁰ per unit; pH 6.2 or more at expiry
1% or 4 per month
FFP
Factor VIII at least 0.7 IU/mL
Monthly
Cryoprecipitate
Factor VIII at least 80 IU and fibrinogen at least 150 mg per unit
Monthly
Leucoreduced products
Residual WBC below 5 × 10⁶ per unit
Monthly
- Reagents
- Daily checks of antisera, AHG and reagent red cells with controls
- Equipment
- Temperature records of refrigerators (2–6 °C), freezers, platelet agitators; centrifuge calibration
- Donor screening
- Kit QC and EQAS for TTI tests
- Records and traceability
- Vein-to-vein tracking; regulation under the Drugs and Cosmetics Act (CDSCO licensing)
Key terms
- Component therapy
- Transfusing only the needed blood component
- Fresh frozen plasma
- Plasma frozen within hours to preserve clotting factors
- Cryoprecipitate
- Cold-insoluble plasma fraction rich in fibrinogen and factor VIII
- Apheresis
- Collection of a specific component by a cell separator
- Leucoreduction
- Removal of white cells from blood components
Quick revision
- Multiple bag systems; light and heavy spins; PRP method.
- Packed, washed, leucoreduced, irradiated, frozen red cells.
- RDP vs SDP; 20–24 °C with agitation, 5 days.
- FFP, cryoprecipitate, cryo-poor plasma; fractionation.
- Plasma expanders; apheresis types and complications; QC standards and activities.
Important exam questions
Practice questions written to the PTU exam pattern for this unit's syllabus: short answers (Section A style) and long answers (Sections B and C style).
Short-answer questions
- Q1.At what temperature are platelets stored?
- Q2.Why are washed red cells given?
- Q3.What does cryoprecipitate contain?
- Q4.How long can FFP be stored?
- Q5.What is plateletpheresis?
- Q6.State the QC standard for a random donor platelet unit.
Long-answer questions
- Q1.Describe the preparation of blood components.
- Q2.Describe platelet and plasma components and their uses.
- Q3.Describe apheresis and quality control in the blood bank.
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