Phlebotomy Test Quality Assurance and Quality Control

Question 1

A Levey-Jennings chart plots control values over time against which reference points?

Accepted Answer

The mean and standard deviations (±1SD, ±2SD, ±3SD) of the control material

Answer

Levey-Jennings charts plot consecutive control values against established mean ±1, 2, and 3 standard deviation (SD) lines, allowing visual detection of trends and rule violations.

Question 2

Westgard's 1₃ₛ rule states that a QC run is rejected when:

Accepted Answer

One control value exceeds ±3SD

Answer

The 1₃s (one-three-sigma) Westgard rule rejects a run when any single control value exceeds 3 standard deviations from the mean, indicating a probable random error.

Question 3

A 'shift' in a Levey-Jennings chart is detected when:

Accepted Answer

Six or more consecutive control values fall on the same side of the mean

Answer

A shift is identified by 6 or more consecutive control values on the same side of the mean (all above or all below), indicating a systematic change in the assay.

Question 4

What is the purpose of a 'delta check' in laboratory quality assurance?

Accepted Answer

To compare a patient's current result with their previous result to detect implausible changes

Answer

Delta checks compare a patient's current result to their previous result; implausible differences flag potential sample mislabeling, wrong patient, or hemolysis errors.

Question 5

Which of the following is a PRE-ANALYTICAL error that can affect laboratory results?

Accepted Answer

Hemolyzed specimen due to difficult venipuncture

Answer

Pre-analytical errors occur before the specimen reaches the analyzer; hemolysis from difficult venipuncture is a classic pre-analytical error that alters multiple analyte values.

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Phlebotomy Test Quality Assurance and Quality Control