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CLIN CHEM LAB > BASIC QUALITY CONTROL STATISTICS > Flashcards

BASIC QUALITY CONTROL STATISTICS Flashcards

1
Q

The mean (or average) is the laboratory’s best estimate of the
analyte’s true value for a specific level of control.

A

Mean

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2
Q

Standard deviation quantifies how close numerical values are
in relation to each other

A

Standard deviation

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3
Q

implies that data points are close to the mean

A

Low SD

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4
Q

implies that data points are spread out over a
large range of values

A

High SD

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5
Q

A graph of all the quality control results in a month

A

Levey Jennings Chart

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6
Q

In levey jenning → in a month, minimum of ____controls should be run

A

20

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7
Q

→ concentrations

A

Y axis

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8
Q

line in the middle

A

Mean

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9
Q

→ days or number of run

A

X axis

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10
Q

→ exactly ___ runs of control in a day (per shift)

A

3

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11
Q

__________ is a measure of variability

A

Coefficient of variation

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12
Q

A method or instrument’s _______ is expressed as a percent

A

Coefficient of variation

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13
Q

A statistic that measures your lab’s bias relative to your
consensus group. An estimate of reliability

A

Standard deviation index

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14
Q

→ Ideal score; Identical to peer group
→ data values of the lab are in 100% agreement with the
reference method

A

SDI - 0

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15
Q

→ acceptable to marginal performance
→ may need to investigate test system bias

A

SDI -1 -1.5

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16
Q

→ marginal performance
→ may need to perform corrective action

A

1.5-2.0

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17
Q

A statistic that compares your lab’s precision to that of other
labs in a consensus group.

A

Coefficient variation of ratio

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18
Q

→ Acceptable performance
→ Indicates that precision is better than peer group

A

Less than 1 - CVR

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19
Q

→ Acceptable to marginal performance
→ May need to investigates test system imprecision

A

1 to 1.5 - CVR

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20
Q

→ Marginal performance
→ May need to perform corrective action

A

1.5-2.0 - CVR

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21
Q

Is defined as abrupt changes in the control values

A

Shift

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22
Q

→ if there is 6 or more consecutive QC results already fall in
the one side of the mean → reject results

A

Shift

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23
Q

● Shifts in QC data represent a sudden and dramatic positive or
negative change in test system performance

A

Shift

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24
Q

Sudden failure or change in the light source

A

Shift

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25
Q

Change in reagent formulation

A

Shift

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26
Q

Change of reagent lot

A

Shift

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27
Q

Major instrument maintenance

A

Shift

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28
Q

Sudden change in incubation temperature (enzymes only)

A

Shift

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29
Q

● Change in room temp. or humidity

A

Shift

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30
Q

Failure in sampling system & reagent dispense system

31
Q

Inaccurate calibration/recalibration

32
Q

Indicated a gradual loss of reliability in the test system

33
Q

→ if there is 6 or more consecutive QC results that slowly but
continually move in one direction → data values are seen
on one side of the mean → reject results

34
Q

Deterioration of the instrument light source

35
Q

Gradual accumulation of debris in sample/reagent tubing

36
Q

Gradual accumulation of debris on electrode surfaces

37
Q

Aging of reagents

38
Q

Gradual deterioration of control materials

39
Q

Gradual deterioration of incubator chamber temp.

40
Q

Gradual deterioration of light filter integrity

41
Q

Gradual deterioration of calibration

42
Q

→ a trend or shift away from the laboratory mean

A

Systematic error

43
Q

→ not acceptable; indicates that there are errors in the
system

A

Systematic error

44
Q

any random deviation away from the laboratory mean

A

random error

45
Q

variations on QC results that shows no pattern

A

random error

46
Q

does not reflect failure on some parts of the testing system

A

random error

47
Q

→ not likely to reoccur

A

random error

48
Q

→ rejected if the data value that showed the random error
exceeds ± 2SD

A

random error

49
Q

If 2 levels of controls

A

Westgard multirule system

50
Q

● a “multi-rule” system developed by _________
based on statistical concepts

A

Dr. James O. Westgard

51
Q

a combination of decision criteria or rules to assess if a
system is in-control

A

Westgard multirule system

52
Q

● use when at least 2 levels of control are run with the
examination run

A

Westgard multirule system

53
Q

● cannot use with only one control

A

Westgard multirule system

54
Q

This is a warning rule that is violated when a single control
observation is outside the ± 2s limits.

55
Q

Two consecutive controls exceed the mean by +/- 2SD

56
Q

4 consecutive controls on one side of the mean exceeds
+/-1SD

57
Q

10 consecutive controls on one side of the mean

58
Q

Improper alignment of sample or reagent pipettes resulting in
change in reagent and calibrator volume.

A

Systematic error

59
Q

● Drift or shift in incubator chamber temperature, deterioration
of photometric light source

A

Systematic error

60
Q

● Change of calibration/reagent lot

A

Systematic error

61
Q

● Deterioration of reagent/calibrator/control product while in
use, storage or shipment

A

Systematic error

62
Q

● Incorrect handling of control product

A

Systematic error

63
Q

Inadequate storage of reagent or calibrators/control products

A

Systematic error

64
Q

Change in test operator

A

Systematic error

65
Q

Any QC result outside ± 3s violates this rule.

66
Q

If there is at least a 4s difference between control values
within a single run, the rule is violated for random error.

67
Q

Power Supply

A

Random error

68
Q

Double pipetting of control sample

A

Random error

69
Q

Misplacement of Control sample within the run

A

Random error

70
Q

Random air bubbles in reagent or sample pipette system

A

Random error

71
Q

Incorrect reconstitution of the control product

A

Random error

72
Q

Inappropriate Storage of control

A

Random error

73
Q

Inadequately mixed reagents

A

Random error

74
Q

Individual operator variation in pipetting , timing , etc.

A

RAndom error

CLIN CHEM LAB (14 decks)

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