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MLS 324 > Quality Control > Flashcards

Quality Control Flashcards

1
Q

closeness to true value

A

Accuracy

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2
Q

ability to yield same numbers, indicated by SD

A

Precision

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3
Q

Controls (QC)

A
  • 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
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4
Q

values assigned by manufacturer (ranges stated in package insert)

A

Assayed Controls

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5
Q

values determined by each lab (ranges recommended by company)

A

Unassayed Controls

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6
Q

Calibration Stability

A
  • time period specifying the validity of an analyzer’s accuracy and/or precision
  • “Standards” of known concentration are used to calibrate analyzers
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7
Q
  • labs determine the lowest and highest values accurately measured on analyzer
  • performed periodically and posted near analyzer
A

Linearity Range

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8
Q

Reference Range (Normal Range)

A
  • 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
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9
Q

Pre-Analytical Variation

A

occurs before the specimen is analyzed

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10
Q

Analytical Variation

A

occurs during the diagnostic testing process

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11
Q

Post-analytical Variation

A

occurs after the test is preformed

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12
Q

checks tor analytical errors, compares current results with previous results

A

Delta Checks

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13
Q

maintenance performed at specified intervals by staff or field engineers

A

Preventative Maintenance

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14
Q

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

A

Turn Around Time

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15
Q

unknown specimens sent to labs and compared against referred values

A

External QC Program

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16
Q

Proficiency Survey

A

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

17
Q

Standard Deviation Index (SDI)

A
  • measure of the difference between several lab QC submissions

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

18
Q

What % of QC points falls within ± 1 SD?

A

68 %

19
Q

What % of QC points falls within ± 2 SD?

A

95 %

20
Q

What % of QC points falls within ± 3 SD?

A

99.7 %

21
Q

2SD

A

SD x 2

22
Q

3SD

A

SD x 3

23
Q

%CV

A

(SD/Mean) x 100

24
Q

Interpretation of QC data involves both ____ and ___ methods.

A

Graphical

Statistical

25
Q

Dates of analyses are plotted along the ___-axis.

A

X

26
Q

QC points are plotted on the ___-axis.

A

Y

27
Q

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

A

Y

28
Q

QC interpretation detects what 2 things?

A
  1. Increased random error

2. Shifts or trends in calibration

29
Q

Random Error

A
  • 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
30
Q

Systematic Error

A
  • 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
31
Q

Westgard Rule 1(2s)

A
  • When one control value exceeds ± 2 SD.

- *Warning Rule

32
Q

Westgard Rule 1(3S)

A
  • When one QC point exceeds ± 3 SD.
  • Patient results and QC values should be rejected and rerun.
  • *Random Error
33
Q

Westgard Rule 2(2S)

A
  • 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
34
Q

Westgard Rule 4(1S)

A
  • 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
35
Q

Westgard Rule: R(4S)

A
  • 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
36
Q

Westgard Rule R(10x) or 10X

A
  • When 10 consecutive QC points fall on one side of the mean.
  • Patient results and QC values should be rejected and rerun.
  • *Systemic Error
37
Q

8x

A

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

38
Q

12x

A

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

MLS 324 (2 decks)

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