Phlebotomy Test Quality Assurance and Quality Control 3

Question 1

The coefficient of variation (CV%) is calculated as:

Accepted Answer

(Standard Deviation ÷ Mean) × 100

Answer

CV% = (SD ÷ Mean) × 100; it expresses precision (reproducibility) as a percentage, allowing comparison across different analytes with different units.

Question 2

In a laboratory with multiple analyzers running the same test, which QA practice ensures consistency of results across instruments?

Accepted Answer

Correlation studies comparing patient or QC results between instruments

Answer

Instrument correlation studies compare results from multiple analyzers to verify they produce equivalent results; significant differences must be investigated and resolved before using both instruments simultaneously.

Question 3

A phlebotomist draws a sample in a lavender-top tube for CBC, but discovers the tube was only three-quarters full. What is the PRIMARY concern?

Accepted Answer

EDTA will be in excess relative to blood volume, causing cell shrinkage and altered CBC values

Answer

Underfilling an EDTA tube causes excess EDTA relative to blood volume, leading to osmotic shrinkage of red blood cells and falsely altered CBC parameters including decreased MCV and hematocrit.

Question 4

Which document type in a laboratory quality management system describes step-by-step instructions for performing a specific procedure?

Accepted Answer

Standard operating procedure (SOP)

Answer

Standard operating procedures (SOPs) provide detailed, step-by-step instructions for performing specific laboratory procedures consistently and correctly.

Question 5

The 'rule of four' regarding pre-analytical errors states that approximately how many laboratory errors occur in the pre-analytical phase?

Accepted Answer

60–70% of all errors

Answer

Studies consistently show that 60–70% of all laboratory errors are pre-analytical, underscoring the critical importance of proper specimen collection and handling.

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Phlebotomy Test Quality Assurance and Quality Control 3