Quality Control

Question 1

Which of the following QC rules are considered indicators of random error?

a. 2-2s

b. R4s

c. 1-3s

d. 4-1s

Answer 1

b. R4s and c. 1-3s

Question 2

Which of the following QC rules is designed to detect a systematic error?
a) 1-2s
b) R4s
c) All rules
d) 4-1s

Answer 2

d) 4-1s

Question 3

What is a trend in the context of QC (Quality Control) and what type of error does it represent?

Answer 3

A trend is a gradual, consistent, and directional change in control data points, indicating a systematic error and a progressive loss of performance in the test system.

Question 4

List common errors that can produce trending data points in clinical chemistry.

Answer 4

Improper reagent stability

Inadequate instrument maintenance

Improper QC material storage or instability

Analyzer malfunction

Calibration drift

Question 5

What is the definition of a “shift” in quality control?

Answer 5

An abrupt change in where the data points sit compared to the mean. It represents a sudden positive or negative change in test system performance and is considered a systematic error.

Question 6

What type of error (random or systematic) is a shift classified as?

Answer 6

Systematic error. This means the error is consistent and predictable, affecting all results in the same direction.

Question 7

List common errors that can produce a shift in QC data.

Answer 7

Improper techniques

Improper reagent stability

Inadequate analyzer maintenance

Analyzer malfunction

Improper QC storage and/or stability

Calibration error

New lot of calibrator

New lot of QC material

New lot of reagent

Improperly established target mean

Question 8

What corrective action should you take if 1-3s is seen with one level of QC but the other level passes?

Answer 8

This is a Westgard rule rejection. You should repeat that level of QC

Question 9

If an assay shows very different results with each QC run, what does this say about the assay’s test performance?

Answer 9

The assay is imprecise