3 - LEVEY-JENNINGS CHART AND WESTGARD RULES

Question 1

evaluates the measurement procedure by periodically assaying QC materials for which the correct result is known in advance

Answer 1

Statistical Quality Control

Question 2

If the result for a QC material is within acceptable limits of the known value,

Answer 2

the measurement procedure is verified to be performing as expected and results for patient samples can be reported with good probability that they are suitable for clinical use

Question 3

Good laboratory practice requires ? that a method is performing correctly at the time patient results are measured

Answer 3

verification

Question 4

The key elements of statistical QC involve

Answer 4

sampling the measurement system using QC samples for which the expected result is known

Question 5

most common presentation for evaluating QC results

Answer 5

Levey-Jennings Chart

Question 6

Levey-Jennings Chart is also called?

Answer 6

Shewhart Plot

Question 7

This format shows each QC result sequentially over time and allows a quick visual assessment of method performance, including trend detection

Answer 7

Levey-Jennings Chart

Question 8

Represents the target (or expected) value for the result

Answer 8

Mean Value

Question 9

these lines represent the expected imprecision for the method

Answer 9

Standard Deviation

Question 10

number of results expected for 1SD

Answer 10

68.3%

Question 11

number of results expected for 2SD

Answer 11

95.4%

Question 12

number of results expected for 3SD

Answer 12

99.7%

Question 13

Interpretation or an individual QC result is based on its ? to be part of the expected distribution of results for the method when the method is performing correctly

Answer 13

probability

Question 14

• one observation exceeds 2SD from the target value
• not recommended because it has an excessive false alert rate

Answer 14

1 2S

Question 15

one observation exceeds 3SD from the target value

Answer 15

1 3S

Question 16

two sequential observations, or observations for two QC samples in the same run, exceed 2SD (or 2.5 SD) from the target value in the same direction

Answer 16

2 2s

Question 17

range between two observations in the same run exceeds 4SD

Answer 17

R 4s

Question 18

• ten sequential observations for the same QC sample are on the same side of the target value (x or mean)
• not recommended because it has an excessive false alert rate

Answer 18

10x

Question 19

eight sequential observations for the same QC sample exceed 1SD (or 1.5SD) in the same direction from the target value

Answer 19

8 1s