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Blood Bank

Blood Component QC

Blood component QC is a systematic process of checks and tests that serves as a final verification of product quality before release. It ensures that components meet established specifications for volume, cellular content, purity (e.g., low residual WBCs), potency (e.g., factor levels, pH), and appearance, ultimately safeguarding patient safety and ensuring the effectiveness of transfusion therapy

This section focuses on Quality Control (QC) as it applies specifically to the final Blood Components prepared in the blood center or transfusion service. QC is a critical part of the overall Quality Management System, ensuring that the components produced consistently meet established standards for safety, purity, potency, and identity before they are released for transfusion

What is Blood Component Quality Control?

  • Definition: A program of specific tests and checks performed on a representative sample of blood components to verify that the collection, processing, storage, and modification procedures consistently yield products meeting predefined specifications
  • Goal: To ensure that every component released for transfusion is likely to be safe and provide its intended therapeutic benefit
  • Distinction from Donor Testing: QC focuses on the characteristics of the final component, whereas donor testing focuses on screening the donor for infectious diseases and determining blood type

Why is Component QC Essential?

  • Patient Safety: Verifies that components are free from unacceptable characteristics (e.g., excessive hemolysis, bacterial contamination, incorrect volume) that could harm a patient
  • Product Efficacy: Confirms that the component contains the expected amount of the therapeutic element (e.g., adequate platelet count, sufficient fibrinogen in Cryo, acceptable Hct in RBCs)
  • Regulatory Compliance: Required by regulatory agencies (FDA - cGMP) and accrediting bodies (AABB Standards)
  • Process Monitoring: Provides ongoing verification that manufacturing processes (e.g., centrifugation speeds/times, leukoreduction filtration, storage conditions) are operating correctly and consistently
  • Consistency: Ensures uniformity between different units of the same component type

Regulatory Framework

  • FDA (21 CFR 606 - cGMP): Requires procedures for assuring the quality of blood products, including testing of representative samples
  • AABB Standards: Provide detailed requirements for QC testing frequencies, sample sizes, and specific parameters for each blood component

General QC Principles Applied to Components

Some QC checks apply broadly:

  • Visual Inspection: Every unit should be visually inspected before issue for:
    • Abnormal color (e.g., excessive hemolysis in RBCs, unusual plasma color)
    • Presence of clots
    • Container integrity (leaks, damage)
    • Presence of turbidity or unusual particulates (esp. in platelets, plasma)
    • Correct labeling (matches records, legible, appropriate format like ISBT 128)
    • Appearance appropriate for the component (e.g., “swirling” in viable platelets)
  • Volume/Weight Checks: Ensuring the volume or weight is within the expected range for the component type
  • Record Review: Confirmation that all required processing and testing steps were completed and acceptable before release

Specific QC Tests for Major Components

AABB Standards typically require QC testing on a specified number or percentage of units produced each month (e.g., 1% of units or 4 units per month, whichever is greater, for many parameters)

  • Red Blood Cells (RBCs)
    • Hematocrit (Hct) or Hemoglobin (Hgb): Must meet minimum/maximum levels depending on the preparation method (e.g., Hct typically ≤ 80% for non-additive units; variable for AS units but often measured)
    • Volume: Checked to ensure consistency
    • Hemolysis: Measured at the end of the storage period (outdate) to ensure it doesn’t exceed acceptable limits (typically <1% of RBC mass)
    • Residual Leukocytes (if Leukoreduced): Must verify that the process consistently produces units meeting the standard (e.g., < 5 x 10⁶ WBCs/unit)
  • Platelets (Apheresis and Pooled WBD)
    • Platelet Count: Must contain the minimum required number of platelets (e.g., ≥ 3.0 x 10¹¹ for apheresis; ≥ 5.5 x 10¹⁰ per individual WBD unit before pooling, with checks on final pool counts)
    • Volume: Checked for consistency
    • pH: CRITICAL. Must be ≥ 6.2 at the end of the allowable storage period (tested at 20-24°C). Low pH indicates poor viability
    • Residual Leukocytes (if Leukoreduced): Must verify process meets standards
    • Bacterial Detection: Increasingly performed routinely (e.g., culture sampling, rapid tests) due to room temperature storage risk. Must show no detectable bacterial contamination per validated methods
    • Visual Inspection: Check for aggregates, abnormal appearance, and presence of swirling
  • Plasma (FFP, PF24, etc.)
    • Volume: Checked for consistency
    • Visual Inspection: Checked after thawing for unusual color, clots, or particulates; container integrity
    • Residual Cells: Limits on contaminating RBCs/WBCs/Platelets may be checked, especially after initial process validation
    • Factor Assays (Less Common Routine QC): Factor VIII or Fibrinogen levels might be checked periodically or during validation to ensure freezing/storage preserves activity, but not typically done on a routine monthly basis like platelet counts
  • Cryoprecipitated AHF (Cryo)
    • Volume: Checked (should be small, 10-20 mL)
    • Fibrinogen Content: REQUIRED QC. Must contain ≥ 150 mg per unit
    • Factor VIII Content: REQUIRED QC. Must contain ≥ 80 IU per unit
  • Granulocytes
    • Volume: Checked
    • Granulocyte Count: Measured to ensure target dose (often > 1.0 x 10¹⁰ per unit), though actual yield varies significantly
    • Red Cell Content: Often assessed to confirm need for crossmatch
    • Sterility: May be performed due to open processing steps or room temperature storage

Frequency and Sampling

  • QC is typically performed on a statistical sampling basis for tests requiring entry into the unit (e.g., cell counts, pH)
  • Frequencies are defined by AABB Standards or internal SOPs (e.g., monthly)
  • Visual inspection and label checks are performed on 100% of units before issue
  • Equipment QC (refrigerator/freezer temps, centrifuge speeds, irradiator dose) is also critical and performed on a regular schedule

Documentation and Corrective Action

  • All QC results must be meticulously documented, reviewed, and signed off by qualified personnel
  • Out-of-specification (OOS) results: require investigation to determine the cause
  • Corrective actions: must be implemented and documented to prevent recurrence
  • If a QC failure indicates a potential problem with multiple units, those units may need to be quarantined or recalled

Key Terms

  • Quality Control (QC): Testing performed on products to verify they meet predefined specifications
  • Specification: A predefined requirement or standard that a product must meet
  • Sampling Plan: A statistically based method for selecting a subset of units for testing
  • Hemolysis: Percentage of red blood cells that have lysed (broken open)
  • pH: Measure of acidity/alkalinity; critical for platelet viability
  • Residual Leukocytes: Number of white blood cells remaining after leukoreduction
  • Bacterial Detection: Testing methods (e.g., culture, rapid tests) to screen for bacterial contamination, especially in platelets
  • Out-of-Specification (OOS): A QC result that does not meet the predefined acceptance criteria
  • Corrective Action: Steps taken to eliminate the cause of a detected nonconformity or other undesirable situation