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Laboratory Management > Quality Control for Quantitative Tests > Flashcards

Quality Control for Quantitative Tests Flashcards

1
Q

measure the quantity of a particular substance in a sample

A

Quantitative Tests

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2
Q

quality control for quantitative tests is designed to assure that patient results are

A

 accurate
 reliable

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3
Q

material that contains the substance being analyzed

A

Control

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4
Q

used to validate reliability of the test system

A

Control

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5
Q

A substance with a specific concentration

A

Calibrators

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6
Q

A substance similar to patients’ samples that has an established concentration.

A

Controls

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7
Q

A calibrator can become a control

A

False

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8
Q

Used in laboratory conditions

A

Controls

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9
Q

Characteristics of Control Materials

A

◼ appropriate for the diagnostic sample
◼ values cover medical decision points
◼ similar to test sample (matrix)
◼ available in large quantity; ideally enough for one year
◼ can store in small aliquots

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10
Q

Types of Control Materials

A

◼ may be frozen, freeze-dried, or chemically preserved
◼ requires very accurate reconstitution if this step is necessary

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11
Q

Sources of Controls Materials

A

◼ commercially prepared
◼ made “in house”
◼ obtained from another laboratory, usually central or reference laboratory

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12
Q

Target value predetermined
Verify and use

A

Assayed Materials

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13
Q

Target value not predetermined
Full assay required before using

A

Unassayed Materials

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14
Q

In-house pooled sera
Full assay, validation

A

In-house Materials

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15
Q

Choosing Control Materials

A

◼ values cover medical decision points
◼ similar to the test sample
◼ controls are usually available in high, normal, and low ranges

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16
Q

Preparation and Storage of Control Material

A

◼ adhere to manufacturer’s
instructions
◼ keep adequate amount
of same lot number
◼ store correctly

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17
Q

Steps in Implementing Quantitative QC

A

◼ obtain control material
◼ run each control 20
times over 30 days
◼ calculate mean and +/-
1,2,3 Standard Deviations

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18
Q

Normal occurrence when a control is tested repeatedly

A

Variability

19
Q

Variability is affected by:

A

Operator technique (Medtech)
Environmental conditions (Environment)
Performance characteristics of the measurement (Machine)

20
Q

Measures of Central Tendency

A

Mean, Median, Mode

21
Q

the value which occurs with the greatest frequency

A

Mode

22
Q

the value at the center or midpoint of the observations

A

Median

23
Q

the calculated average of the values

A

Mean

24
Q

Not all central values are the same

A

True

25
Q

characteristic “bell-shaped” curve

A

Normal Distribution

26
Q

used to monitor
the accuracy and the precision of the assay.

A

Quality Control

27
Q

The closeness of measurements to the true value

A

Accuracy

28
Q

The amount of variation in the measurements

A

Precision

29
Q

The difference between the expectation of a test result and an accepted reference value

A

Bias

30
Q

Accurate is always precise

A

True

31
Q

Precise is not always Accurate

A

True

32
Q

For a set of data with a
normal distribution, a
random measurement
will fall within:

A

+ 1 SD 68.3% of the time
+ 2 SD 95.5% of the time
+ 3 SD 99.7% of the time

33
Q

principle measure of
variability used in the laboratory

A

Standard Deviation

34
Q

SD expressed as a percentage of the mean.

A

Coefficient of variation

35
Q

Graphically Representing Control Ranges

A

Levey-Jennings Chart

36
Q

results with no pattern-only a cause for rejection if outside 2SDs

A

random error

37
Q

not acceptable, correct the source of error

A

systematic error

38
Q

control on one side of the mean 6 consecutive days

A

shift

39
Q

control moving in one direction–heading toward an “out of control” value

A

trend

40
Q

represents a range of values in which the true value is reasonably expected to lie

A

Measurement Uncertainty

41
Q

Measurement Uncertainty is estimated at

A

95% coverage

42
Q

If QC is out of control

A

STOP testing
Do not report patient results until problem is solved

43
Q
A

Laboratory Management (9 decks)

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