5.2 Specimen Processing & Quality Assurance

Specimen processing is the bridge between collection and laboratory analysis. Proper processing techniques ensure the integrity of the specimen and the accuracy of test results. Quality assurance programs provide systematic oversight of the entire testing process.

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Centrifugation

Centrifugation uses centrifugal force to separate blood into its components based on density. The heavier cellular components (RBCs, WBCs, platelets) settle to the bottom, while the lighter liquid component (serum or plasma) rises to the top.

Serum vs. Plasma

Clotting Times Before Centrifugation

Centrifugation Guidelines

• Standard speed: 1,000-2,000 x g (relative centrifugal force) for 10-15 minutes
• Ensure the centrifuge is properly balanced (equal tube weights on opposite sides)
• Never open the centrifuge lid while it is spinning
• After centrifugation, the gel separator in SST tubes forms a barrier between serum and cells

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Aliquoting

Aliquoting is the process of transferring separated serum or plasma from the original tube to a secondary (aliquot) tube:

• Use a disposable transfer pipette — never pour from one tube to another
• Label the aliquot tube with the same patient information as the original
• Aliquoting is performed when:
  • Multiple departments need the same specimen
  • The specimen must be stored or frozen for later testing
  • A send-out laboratory requires a specific container
• Avoid transferring any cells or gel into the aliquot tube

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Serum vs. Plasma — Understanding the Difference

This is a commonly tested concept on the NHA CPT exam:

Serum

• Produced from clotted blood (red top, gold SST)
• Blood is allowed to clot, then centrifuged
• Does NOT contain fibrinogen or clotting factors (they were consumed during clotting)
• Appears as a clear, straw-yellow liquid above the clot
• Used for most chemistry tests, serology, and immunology

Plasma

• Produced from anticoagulated blood (green, lavender, light blue)
• Blood is prevented from clotting by the anticoagulant
• DOES contain fibrinogen and clotting factors
• Appears as a clear, straw-yellow liquid above the packed cells
• Used for coagulation tests, stat chemistry, some immunology tests

Key Differences at a Glance

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Specimen Integrity Indicators

Modern laboratory analyzers can detect specimen quality issues automatically:

These indicators (collectively called the HIL index) are reported with test results when they may affect accuracy. The laboratory may request a recollection if interference is significant.

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Specimen Rejection Criteria

Laboratories reject specimens that do not meet quality standards. Common rejection reasons:

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Laboratory Test Panels

Phlebotomists should be familiar with common test panels (groups of tests ordered together):

Basic Metabolic Panel (BMP) — 8 Tests

Comprehensive Metabolic Panel (CMP) — 14 Tests

• All 8 BMP tests PLUS:
• Albumin, total protein, alkaline phosphatase (ALP), ALT, AST, and total bilirubin
• Assesses liver function in addition to kidney function and electrolytes

Complete Blood Count (CBC)

Lipid Panel

Coagulation Panel

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Quality Assurance (QA)

Quality assurance encompasses all activities that ensure reliable laboratory results throughout the total testing process:

Three Phases of the Testing Process

Key Fact: The preanalytical phase accounts for 46-68% of all laboratory errors — this is the phase that phlebotomists directly control.

Delta Checks

A delta check compares a patient's current test results with their previous results:

• If the current result differs significantly from the historical result, the system flags it for review
• Delta checks help identify:
  • Specimen mislabeling (results don't match the patient's history)
  • Significant clinical changes (genuine medical deterioration or improvement)
  • Technical errors (wrong tube, hemolysis, contamination)

Lab Requisition Forms

Every blood collection must be accompanied by a lab requisition form (paper or electronic) that includes:

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Quality Control (QC) vs. Quality Assurance (QA)

Understanding the difference between QC and QA is important for the exam:

Preanalytical Quality Indicators

CLIA (Clinical Laboratory Improvement Amendments)

CLIA regulates all clinical laboratory testing in the United States:

Key Fact: Many POCT (point-of-care) tests that phlebotomists may perform are CLIA-waived, but they still require proper training, quality control, and documentation.

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Critical Values

Critical values (also called panic values or alert values) are test results that indicate a life-threatening condition requiring immediate physician notification:

Common Critical Values

Critical Value Reporting Protocol

1. Verify the result — rerun the test if there is any question
2. Call the ordering physician or authorized provider within 30 minutes of result verification
3. Document the following:
   • Date and time of the call
   • Who was notified (name and title)
   • The critical value reported
   • Read-back confirmation (the recipient must repeat the value back)
4. If the physician cannot be reached, follow the facility's escalation protocol

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Medical Terminology for Phlebotomists

Phlebotomists should know common medical terminology related to blood and laboratory testing:

Blood-Related Prefixes and Suffixes

Common Abbreviations

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Point-of-Care Testing (POCT)

Point-of-care testing (also called bedside testing or near-patient testing) provides rapid results at or near the patient:

Common POCT Tests

POCT Quality Requirements

• Operator training required — documented competency assessment
• Quality control (QC) must be run per manufacturer guidelines (daily, with each new lot, etc.)
• Results must be documented in the patient's medical record
• Proficiency testing — POCT instruments must participate in external quality assessment programs
• Instrument maintenance — cleaning, calibration per manufacturer schedule