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Blood Bank

Quality Assessment/Troubleshooting

The safety of transfusion medicine relies on a multi-layered Quality Management System (QMS). Because blood is classified as both a biological product and a drug, Blood Bank is subject to stricter regulations than any other section of the clinical laboratory. This overview synthesizes the critical components of the workflow, daily quality control, and regulatory compliance required for an entry-level laboratory scientist

The Total Process of Workflow

Quality Assessment (QA) spans the entire lifecycle of the specimen and the blood product, divided into preanalytical, analytical, and postanalytical phases. An error in any phase can lead to a fatal hemolytic transfusion reaction, with preanalytical errors being the most common cause of morbidity

Preanalytical Phase (Specimen & Collection)

This phase involves all steps prior to the actual testing. The primary objective is to ensure positive patient identification and specimen integrity

  • Patient Identification: The “Zero Tolerance” policy applies here. Specimens must have at least two unique identifiers (e.g., Name, MRN/DOB). The phlebotomist must sign the tube to attest to identity verification. Mislabeled tubes are rejected immediately; they are rarely corrected to prevent “wrong blood in tube” (WBIT) errors
  • The 3-Day Rule: For patients with a history of pregnancy or transfusion in the last 3 months (or unknown history), the sample is valid for only 3 days. This ensures the test reflects the patient’s current immunological status, capturing any newly developed antibodies
  • Specimen Rejection
    • Hemolysis: Rejected because mechanical hemolysis masks the detection of complement-mediated hemolysis (a positive result) during testing
    • Labeling Discrepancies: Any mismatch between the tube and the requisition results in rejection

Analytical Phase (Testing)

This phase encompasses the actual serological performance. It relies on validated techniques, functioning equipment, and potent reagents to ensure accuracy (true value) and precision (reproducibility)

  • Technique Standards: Adherence to Standard Operating Procedures (SOPs) is mandatory. This includes using appropriate cell suspension concentrations (2-5%), incubation times, and centrifugation speeds
  • Reagent Validation: Ensuring that antisera and cells react as expected (discussed further in Quality Control)
  • Proficiency Testing: The external verification of the analytical phase

Postanalytical Phase (Reporting & Issuance)

This phase involves the interpretation of data, the management of records, and the physical release of blood products

  • LIS Logic (Truth Tables): The Laboratory Information System acts as a safety barrier. It uses logic tables to flag incompatibilities (e.g., preventing the crossmatching of Group A cells for a Group O patient)
  • Visual Inspection: Prior to release, units are inspected for abnormal color (bacterial contamination), clots, or leakage. This is the final check before the product reaches the patient
  • Traceability: Documentation must link the donor unit to the recipient. Records of traceability are generally kept for a minimum of 10 years, while patient records regarding difficulty in typing or unexpected antibodies are kept indefinitely

Quality Control (QC)

While QA looks at the big picture, QC is the specific, daily testing of reagents and equipment to validate immediate reliability. If QC fails, patient testing must stop until the issue is resolved

Reagent QC

All reagents (Anti-A, Anti-B, Anti-D, Reagent Cells) must be tested daily to verify two characteristics: Potency (ability to detect the antigen) and Specificity (ability to remain negative when the antigen is absent)

  • Visual Check: Reagents are inspected for turbidity or precipitate, which suggests bacterial contamination
  • Anti-Human Globulin (AHG) & Check Cells: AHG is the most critical reagent for antibody detection
    • The Check Cell Rule: All negative AHG reactions must be validated by adding IgG-sensitized red cells (Check Cells/Coombs Control)
    • Interpretation: Check cells must agglutinate. This proves the AHG was added, it was active, and the cell washing was adequate. If check cells are negative, the test is invalid (false negative) and must be repeated

Equipment QC

  • Centrifuges: Calibrated for speed (RPM) and time. The “Optimal Spin” is determined to create a button that is distinct but easily resuspended. Over-centrifugation causes false positives; under-centrifugation causes false negatives
  • Temperatures
    • Water Baths/Heat Blocks: \(37^\circ\text{C}\) (Body temperature for IgG reactions)
    • Refrigerators: \(1^\circ\text{C}\) to \(6^\circ\text{C}\) (Storage limit to prevent bacterial growth while maintaining viability)
    • Freezers: \(\le -18^\circ\text{C}\) (Plasma preservation)
    • Alarms: Must be tested periodically to ensure they trigger before storage units reach unsafe temperatures

Component QC

  • Platelets: Must be stored at room temperature (\(20\text{-}24^\circ\text{C}\)) with agitation. QC includes pH testing (\(\ge 6.2\)) and mandatory bacterial detection prior to issue
  • Leukoreduction: QC must verify the removal of WBCs (\(< 5.0 \times 10^6\) residual WBCs) to prevent febrile reactions and HLA alloimmunization

Regulation & Compliance

Blood Banks operate under the jurisdiction of the FDA (because blood is a drug/biologic), CMS (CLIA), and accrediting bodies like AABB and CAP

Proficiency Testing (PT)

PT is an external quality assessment mandated by CLIA to verify laboratory accuracy against peer groups

  • Process: The lab receives “unknown” samples 3 times a year. These must be tested exactly like patient samples (no special treatment)
  • The Golden Rule: There is a strict prohibition on communicating results with other laboratories before the submission deadline. Sharing results is considered “PT Referral” and can result in the revocation of the laboratory’s license and a ban on the directors/owners

Competency Assessment

This validates the skill of the personnel, distinct from the validation of the test method. CLIA requires assessment semiannually for the first year of employment, then annually thereafter. It must include six specific elements:

  1. Direct observation of testing
  2. Monitoring of recording/reporting
  3. Review of test results/worksheets
  4. Direct observation of maintenance
  5. Testing of known samples (PT or blind samples)
  6. Assessment of problem-solving skills

Troubleshooting & Corrective Action

When QC fails or errors occur, a standardized response is required

  • Immediate Action: Repeat the test to rule out random error. If that fails, change reagents. If that fails, check equipment
  • Root Cause Analysis (RCA): A retrospective investigation to find the underlying cause of an error (e.g., “Why was the unit mislabeled?” rather than just “Who mislabeled it?”)
  • Corrective Action: Remedial steps taken to fix the immediate problem (e.g., discarding a contaminated reagent vial)
  • Preventative Action: Systemic changes to ensure the error does not recur (e.g., implementing barcode scanning)