Quality Control

Question 1

closeness to true value

Answer 1

Accuracy

Question 2

ability to yield same numbers, indicated by SD

Answer 2

Precision

Question 3

Controls (QC)

Answer 3

• used to monitor accuracy and precision of patient results
• typically a commercial (synthetic) material analyzed along side patients to assess analyzer function
• controls MUST be within range in order to report patient results

Question 4

values assigned by manufacturer (ranges stated in package insert)

Answer 4

Assayed Controls

Question 5

values determined by each lab (ranges recommended by company)

Answer 5

Unassayed Controls

Question 6

Calibration Stability

Answer 6

• time period specifying the validity of an analyzer’s accuracy and/or precision
• “Standards” of known concentration are used to calibrate analyzers

Question 7

• labs determine the lowest and highest values accurately measured on analyzer
• performed periodically and posted near analyzer

Answer 7

Linearity Range

Question 8

Reference Range (Normal Range)

Answer 8

• calculated by each lab for each test
• typically a minimum of 25 “healthy” patients are analyzed and statistical calculations are performed, such as mean and SD to determine ranges

Question 9

Pre-Analytical Variation

Answer 9

occurs before the specimen is analyzed

Question 10

Analytical Variation

Answer 10

occurs during the diagnostic testing process

Question 11

Post-analytical Variation

Answer 11

occurs after the test is preformed

Question 12

checks tor analytical errors, compares current results with previous results

Answer 12

Delta Checks

Question 13

maintenance performed at specified intervals by staff or field engineers

Answer 13

Preventative Maintenance

Question 14

how quickly a lab can complete the analysis of a test -request to result

Answer 14

Turn Around Time

Question 15

unknown specimens sent to labs and compared against referred values

Answer 15

External QC Program

Question 16

Proficiency Survey

Answer 16

consists of specifically prepared unknown specimens (proficiency samples), shipped to labs by independent manufacturer, labs analyze unknown samples and submit results

Question 17

Standard Deviation Index (SDI)

Answer 17

• measure of the difference between several lab QC submissions

SDI = (value - group mean)/group standard deviation

Question 18

What % of QC points falls within ± 1 SD?

Answer 18

68 %

Question 19

What % of QC points falls within ± 2 SD?

Answer 19

95 %

Question 20

What % of QC points falls within ± 3 SD?

Answer 20

99.7 %

Question 21

2SD

Answer 21

SD x 2

Question 22

3SD

Answer 22

SD x 3

Question 23

%CV

Answer 23

(SD/Mean) x 100

Question 24

Interpretation of QC data involves both ____ and ___ methods.

Answer 24

Graphical

Statistical

Question 25

Dates of analyses are plotted along the ___-axis.

Answer 25

X

Question 26

QC points are plotted on the ___-axis.

Answer 26

Y

Question 27

The mean, ± 1 SD, ± 2 SD, and ± 3 SD limits are marked on the ___-axis.

Answer 27

Y

Question 28

QC interpretation detects what 2 things?

Answer 28

1. Increased random error | 2. Shifts or trends in calibration

Question 29

Random Error

Answer 29

- Affects the reproducibility or PRECISION of a test system. - Can occur with: # variations in voltage # pipette techniques # dispensers # contamination # volume dispensed # bubbles in lines of reagents, etc. - Detected with 1(3s) or R(4s) Westgard Rules

Question 30

Systematic Error

Answer 30

- Affects the ACCURACY of the test system in terms of bias, shifts and trends. - Can occur with: # calibration changes # temperature changes # light source deterioration # electronics # reagent lot changes, etc. - Detected with 2(2s), 4(1s), or 10(x) Westgard Rules

Question 31

Westgard Rule 1(2s)

Answer 31

- When one control value exceeds ± 2 SD. | - *Warning Rule

Question 32

Westgard Rule 1(3S)

Answer 32

- When one QC point exceeds ± 3 SD. - Patient results and QC values should be rejected and rerun. - *Random Error

Question 33

Westgard Rule 2(2S)

Answer 33

- When 2 consecutive QC points exceed + 2 SD or -2 SD on the same side of mean. - Patient results and QC values should be rejected and rerun. - *Systemic Error

Question 34

Westgard Rule 4(1S)

Answer 34

- When 4 consecutive QC points fall on the same side of the mean. - Patient results and QC values should be rejected and rerun. - *Systemic Error

Question 35

Westgard Rule: R(4S)

Answer 35

- When one QC point exceeds the mean + 2 SD and another exceeds the mean – 2 SD (opposite sides of the mean). - Patient results and QC values should be rejected and rerun. - *Random Error

Question 36

Westgard Rule R(10x) or 10X

Answer 36

- When 10 consecutive QC points fall on one side of the mean. - Patient results and QC values should be rejected and rerun. - *Systemic Error

Question 37

8x

Answer 37

reject when 8 consecutive control measurements fall on one side of the mean

Question 38

12x

Answer 38

reject when 12 consecutive control measurements fall on one side of the mean