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Clinical Chem > LESSON 3: QUALITY CONTROL > Flashcards

LESSON 3: QUALITY CONTROL Flashcards

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1
Q

QC in the laboratory involves the systematic monitoring of _____ to detect _____

A

analytic processes, analytic errors

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2
Q

Specimens analyzed for QC purposes are known as

A

QC materials

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3
Q

QC materials must be available in sufficient quantity to last for extended periods of time determined by

A

QC material stability and vendor determined expiration dates

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4
Q

PARAMETERS OF QUALITY CONTROL: (7)

A
  1. Sensitivity
  2. Specificity
  3. Accuracy
  4. Precision or Reproducibility
  5. Reliability
  6. Diagnostic Sensitivity
  7. Diagnostic Specificity
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5
Q

it is the ability of an analytical method to measure the smallest concentration of the analyte of interest

A

Sensitivity

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6
Q

it is the ability of an analytical method to measure only the analyte of interest

A

Specificity

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7
Q

the nearness or closeness of the assayed value to the true or target value.

A

Accuracy

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8
Q

the ability of an analytical method to give repeated results on the same samples that agree with one another.

A

Precision or reproducibility

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9
Q

the ability of an analytical method to maintain accuracy and precision on the extended period of time.

A

Reliability

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10
Q

it is the ability to detect the proportion of individuals with the disease who test positively with the test.

A

Diagnostic sensitivity

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11
Q

Diagnostic sensitivity (%) Formula

A

100 x number of diseased individuals / total number of individuals tested w/o the disease

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12
Q

Diagnostic specificity (%) Formula

A

100 x the number of individuals without the disease with a negative test / total number of individuals tested w/o the disease

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13
Q

Kinds of Quality Control:

A
  1. Intralab (internal QC)
  2. Interlab (external QC)
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14
Q

Involves the analyses of control samples together with the patient specimens. It detects changes in the performance between the present operation and the stable operation. It is important for the daily monitoring accuracy and precision of analytical method

A

Intralab (internal QC)

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15
Q

Intralab detects both ___ and ___ errors

A

random and systematic errors

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16
Q

It involves proficiency testing programs that periodically provide samples of unknown concentration of analytes to participating laboratories.
it is important in maintaining long-term accuracy of the analytical methods

A

Interlab

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17
Q

Objectives of quality control:

A
  1. To check the stability of the machine
  2. To check the quality of reagents
  3. To check the technical errors.
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18
Q

Characteristics of an ideal QC Material

A
  1. Resembles human sample
  2. Inexpensive and stable for long periods
  3. No communicable disease
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19
Q

Quality Control bottle cap COLOR for ABNORMAL LOW

A

Blue

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20
Q

Quality Control bottle cap COLOR for ABNORMAL HIGH

A

Red or Black

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21
Q

Quality Control bottle cap COLOR for NORMAL

A

Green or White

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22
Q

Sources of QCM:

A
  1. In-house QCM
  2. Commercial QCM
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23
Q

In-house QCM are usually from ____ or ____

A

Human or Bovine (Cow)

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24
Q

In-house QCM, 3 types

A
  1. Pooled sera
  2. Fasting donor sera
  3. Blood bank plasma
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25
Q

Pooled sera is describes as ___ sera

A

Left over sera

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26
Q

Pooled sera is froze for ___ hours at ___ °C

A

72h at -20°C

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27
Q

Pooled sera is allowed to thaw at __°C for __ hours

A

6°C for 16 hours

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28
Q

Pooled sera is not for

A
  1. Not for immunochemistry assays – some bovine protein differs from human
  2. Not for dye-binding procedures for albumin
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29
Q

2 types of Commercial QCM

A
  1. Lyophilized form
  2. Non-lyophilized form (liquid)
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30
Q

Pooled sera has specific temperature and time to kill ____

A

bacteria

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31
Q

Lyophilized form: ___°C; freezing (best storage); shelf life: ___ hrs.; preparation:

A

2-8°C;24 hrs

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32
Q

Lyophilized form is stored in an _____ due to its sensitivity to light

A

amber bottle

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33
Q

Lyophilized form is diluted with ____

A

distilled water

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34
Q

If non-lyophilized form has jelly, it is ____

A

contaminated

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35
Q

it is important for non-lyophilized form to be clear, serum color, and for its ___ part to be checked

A

bottom part

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36
Q

true or false. Non-lyophilized form from refregirator can be used right away

A

false, it must be room temp

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37
Q

Commercial QCM that is in liquid form

A

Non-lyophilized form

38
Q

VARIATIONS IN QUALITY CONTROL

A
  1. Random Error
  2. Systematic Error
  3. Clerical Error
39
Q

In determining error or imprecision. It is the basis of varying differences between repeated measurements.

A

Random error

40
Q

Random error is due to

A

instrument, operator and environmental conditions

41
Q

Random error. Variation techniques:

A

Pipetting error
Mislabeling of samples
Temperature fluctuations
Improper mixing of samples and reagents

42
Q

Inaccuracy.It is an error that influences observations consistently in one direction. It detects positive and negative bias, often related to calibration problem, inadequate reagent blanks, leaky ISE, failing instrumentation and poorly written procedure.

A

Systematic error

43
Q

The highest frequency of this error occurs with the use of a handwritten labels and request forms.

A

Clerical error

44
Q

a measure of central tendency. It is associated with symmetrical or normal distribution. It measures accuracy or system error.

A

Mean

45
Q

is calculated by summing the observations and dividing by the number of the critically evaluated observations.

A

Mean

46
Q

a measure of the dispersion of values from the mean. It helps describe the normal curve. It measures precision or random error. the most frequently used measure of variation

A

Standard deviation

47
Q

where the numbers that you need to calculate are the entire population./ parameters ,fixed value

A

Population SD

48
Q

calculated from only some of the individuals in a population./ statistics

A

Sample SD

49
Q

it is called standard deviation squared; a measure of variability

A

Variance

50
Q

it is the value of observation that divides the observation into two groups, each containing equal number of observations

A

Median

51
Q

it is the most frequent observation.

A

Mode

52
Q

it is used to determine whether there is a statistical significant difference between the means of two groups of data.

A

T – test

53
Q

it is used to determine whether here is statistically significant difference between the standard deviations of two groups of data.

A

F – test

54
Q

graphically represent the observed values of a control material over time in the context of the upper and lower control limits in relation to the target value.

A

Control charts

55
Q

_____ in the clinical laboratory is used to monitor the analytic variations that can occur

A

QC system

56
Q

The QC program can be thought of as a three-stage process:

A
  1. Establishing or verifying allowable statistical limits of variation
  2. Using these limits as criteria for evaluating the QC data generated for each test
  3. Acting to remedy errors real time when indicated
    a. Finding the cause(s) of error
    b. Taking corrective action
    c. Reanalyzing control and patient data
57
Q

TYPES OF QC CHARTS

A
  1. Gaussian curve
  2. Cumulative sum graph
  3. Youden/ twin plot
  4. Shewhart Levey-Jennings chart
58
Q

Type of chart that is used to visualize accuracy and precision
It occurs when the data set can be accurately described by the SD and the mean. It focuses on the distribution of errors from the analytical method rather than the value from a healthy or patient population

A

Gaussian curve

59
Q

Type of chart that calculates the difference between QC results and the target means.
The most common method is the V-mask; require computer implementation
It identifies consistent bias problems.

A

Cumulative sum graph

60
Q

It is used to compare results obtained on a high a low control serum from different laboratories

A

Youden/ twin plot

61
Q

Most widely used QC chart in the clinical laboratory
It allows the laboratories to apply multiple rules without the aid of a computer.

A

Shewhart Levey-Jennings chart

62
Q

Errors which can be observed on LJ chart:

A

Trend
Shift
Outliers

63
Q

It is a gradual lost of reliability, formed by control values that either increase or decreased for six consecutive days
Main cause: deterioration of reagent

A

Trend

64
Q

Trend. Main cause:

A

deterioration of reagent

65
Q

it is formed by control values that distribute themselves on one side or either side of the mean for six consecutive days

A

Shift

66
Q

Shift. Main cause:

A

improper calibration of the instrument

67
Q

In Shift, __ or more consecutive data points are either all above or below the median constitute

A

6

68
Q

In Trend, __ data points are all going up or down constitutes

A

5

69
Q

These are control values that are far from the main set of values

A

Outliers

70
Q

Outliers. Main cause:

A

random or systematic errors

71
Q

It recognized the use of simple upper and lower limits are not enough to identify analytical problems

A

Westgard control rules

72
Q

refers to a control rule that is commonly used with a Levey-Jennings chart when the control limits are set as the mean plus 3s and the mean minus 3s. A run is rejected when a single control measurement exceeds the mean plus 3s or the mean minus 3s control limit.

A

13s

73
Q

refers to the control rule that is commonly used with a Levey-Jennings chart when the control limits are set as the mean plus/minus 2s. In the original Westgard multirule QC procedure, this rule is used as a warning rule to trigger careful inspection of the control data by the following rejection rules.

A

12s

74
Q

reject when 2 consecutive control measurements exceed the same mean plus 2s or the same mean minus 2s control limit.

A

22s

75
Q

reject when 1 control measurement in a group exceeds the mean plus 2s and another exceeds the mean minus 2s. This rule should only be interpreted within-run, not between-run. The graphic below should really imply that points 5 and 6 are within the same run.

A

R4s

76
Q

reject when 4 consecutive control measurements exceed the same mean plus 1s or the same mean minus 1s control limit.

A

41s

77
Q

reject when 10 consecutive control measurements fall on one side of the mean.

A

10x

78
Q

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

A

8x

79
Q

reject when 2 out of 3 control measurements exceed the same mean plus 2s or mean minus 2s control limit;

A

2of32s

80
Q
  • reject when 3 consecutive control measurements exceed the same mean plus 1s or mean minus 1s control limit
A

31s

81
Q

reject when 6 consecutive control measurements fall on one side of the mean.

A

6x

82
Q

reject when 9 consecutive control measurements fall on one side of the mean.

A

9x

83
Q

______ is another tool in the ongoing process of monitoring test performance

A

proficiency testing

84
Q

Acceptable performance in ______ is required by the CAP, the CLIA, (Clinical Laboratory Improvement Amendments and the College of American Pathologists)

A

proficiency testing programs

85
Q

Method used to validate a particular measurement process. The results are compared with other external laboratories to give an objective indication of test accuracy.

A

Proficiency test

86
Q

Specimens that have known concentrations of an analyte for the test of interest. The testing laboratory does not know the targeted concentration when tested

A

Proficiency samples

87
Q

is one of the measures by the Department of Health (DOH) to assess the reliability of laboratory diagnosis and maintain quality assurance of licensed clinical chemistry laboratories in the country.

A

The National External Quality Assessment Scheme (NEQAS)

88
Q

Variations in QC: No error = ?

A

✔ accuracy
✔ precision

89
Q

Variations in QC: Random error = ?

A

✔ accuracy
✘ precision

90
Q

Variations in QC: Systematic error = ?

A

✘ accuracy
✔ precision

Clinical Chem (4 decks)

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