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Clinical Chemistry > QUALITY CONTROL > Flashcards

QUALITY CONTROL Flashcards

1
Q

Ability of analytical method to measure the smallest concentration of analyte

A

Sensitivity

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2
Q

Ability of analytical method to measure only the analyte of interest

A

Specidicity

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3
Q

Nearness or closeness of the assayed value to the true or target value

A

Accuracy

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4
Q

Ability of analytical method to give repeated results on the same sample

A

Precision or Reproducivility

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5
Q

Degree by which a method is easily repeated

A

Practicability

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6
Q

Ability to maintain accuracy and precision over an extended period of time

A

Reliability

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7
Q

Ability of analytical method to detect proportion of individuals without the disease

A

Diagnostic Specificity

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8
Q

Ability of analytical method to detect proportion of individuals with the disease

A

Diagnostic Sensitivity

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9
Q

Sensitivity (%)

A

100 x number of true positive / total number of diseased

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10
Q

Specificity (%)

A

100 x number of true negative / total number of without disease

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11
Q

Error due to chance, varies from sample to sample

A

Random Error

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12
Q

Due to instrument, operator and environmental conditions such as:
> pipetting error
> mislabeling of samples
> temperature fluctuation
> improper mixing of sample and reagent

A

Random Error

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13
Q

Error that influences observations consistently in one direction

A

Systematic Error

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14
Q

Due to:
- Calibration problems
- Deterioration of reagents and control materials
- Improperly made standard solutions
- Contaminated solutions
- Unstable and Inadequate reagent blanks
- Leaky ion selective electrode
- Failing instrumentation and
- Poorly written procedures

A

Systematic Error

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15
Q

Difference between the target value and the assayed value

A

Constant Error

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16
Q

Results in greater deviation from the target value due to higher sample concentration

A

Proportional/ Slope/ Percent Error

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17
Q

Highest frequency of Clerical errors occurs with

A

Use of handwritten labels and Request forms

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18
Q

Objectives of Quality Control

A
  1. Check stability of the machine
  2. Check quality of reagents
  3. Check technical errors
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19
Q

Levels of control solutions in General Chemistry

A

TWO levels

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20
Q

Levels of control solutions in Immunoassays

A

THREE levels

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21
Q

Characteristics of an Ideal QC material

A
  1. Resembles human sample
  2. Inexpensive and stable for long periods
  3. No communicable diseases
  4. No matrix effects
  5. With known analyte concentrations
  6. Convenient packaging for easy dispensing and storage
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22
Q

Incorrect patient identification
Improper patient preparation
Incorrect specimen collection
Mislabeled specimen
Incorrect order of draw
Incorrect used of tubes for blood collection
Incorrect anticoagulant to blood ratio
Improper mixing of blood and anticoagulant
Incorrect specimen preservation
Mishandled specimen
Incorrectly interpreted/ ordered laboratory test
Incomplete centrifugation
Incorrect data login

A

Pre-Analytical Errors

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23
Q

Incorrect sample and reagent volume
Incorrect incubation of solution
Equipment/ Instrument malfunction
Improper calibration of equipment/ Calibration errors

A

Analytical Errors

24
Q

Unavailable or delayed laboratory results
Long turnaround time
Incomplete laboratory results
Wrong transcription of the patient’s data and laboratory results
Missing laboratory results
Laboratory results submitted to the wrong physician/ doctors who did not request for the lab test

A

Post-analytical Errors

25
Q

Most laboratory errors occur in:

A

Pre-Analytic and Post-Analytic stages

26
Q

Occurs when the data set can be accurately described by the SD and the MEAN
obtained by plotting the values from multiple analyses of a sample

A

Gaussian Curve/ Bell-Shaped Curve

27
Q

Calculates the difference between QC results and the target means
Identifies consistent bias problems
Very sensitive to small persistent errors that commonly occur in the modern, low calibration-frequency analyzer

A

Cumulative Sum Graph (CUSUM)

28
Q

Used to compare results obtained on a high and low control serum from different laboratories

A

Youden/ Twin Plot

29
Q

Most widely used QC chart in the clinical laboratory
Allows the laboratorians to apply multiple rules without the aid of a computer
Easily identifies random and Systematic Errors

A

Shewhart Levey-Jenning Chart

30
Q

Error in LJ Chart:
formed by control values that either increase or decrease for 6 consecutive days
MC: Deterioration of reagents

A

Trend

31
Q

Error in LJ Chart:
formed by control values that distribute themselves on one side or either side of the mean for 6 consecutive days
MC: Improper calibration of the instrument

A

Shift

32
Q

Error in LJ Chart:
control values that are far from the main set of values
highly deviating values
caused by random or systematic errors

A

Outliers

33
Q

Recognizes that the use of simple upper and lower control limits is not enough to identify analytical problems

A

Westgard Control Chart

34
Q

Used as a rejection or warning rule when one control result exceeds the mean +-2SD

A

1 2s

35
Q

Observed when one control result exceed the mean +- 3SD
due to RANDOM error

A

1 3s

36
Q

Observed when last 2 control results exceed either the mean +- 2 SD
due to SYSTEMATIC error

A

2 2s

37
Q

Last four consecutive control results exceeds either mean +- 1SD
due to SYSTEMATIC error

A

4 1s

38
Q

Range of difference between the highest and lowest control result within an analytical run exceeds 4s
due to SYSTEMATIC error

A

R 4s

39
Q

Westgard test method

A

at least 40 samples

40
Q

Westgard Reference method

A

at least 100 samples

41
Q

Acceptable reference limit is set at

A

+- 2SD or 95%

42
Q

Set of control and patient specimen assayed, evaluated and reported together

A

Analytical run

43
Q

Most commonly used patient based-QC techniques
Difference between two consecutive measurements of the same analyte on the same individual

A

Delta check

44
Q

Used to measure systematic errors or inaccuracy caused by substances other than the analyte

A

Interference experiments

45
Q

Concentration range over which the measured concentration is equal to the actual concentration without modification of the method

A

Linear range/ Dynamic Range

46
Q

Sometimes referred to as absurd value
Helps detect sample contamination or dilution, inadequate sample volume, inadequate reagent volumes, sudden major problems with the method, or incorrect recording or transmission of the result

A

Physiologic Limit

47
Q

Type of analytical testing performed outside the confines of the central laboratory, usually by nonlaboratorian personnel

A

Point Of Care Testing (POCT)/
Decentralized Testing

48
Q

Most commonly used POCT

A

Use of portable whole blood glucose meters for the management of patients with diabetes mellitus

49
Q

Systematic Action necessary to provide adequate confidence that laboratory services will satisfy the given medical needs for the patient

A

Quality Assurance

50
Q

Can be envisioned as a tripod with three legs

A

Program development
Assessment and Monitoring
Quality Improvement

51
Q

Primary Goal of QA

A

To deliver quality services and products to customers

52
Q

Includes effective test request forms, Clear instruction for patient preparation and specimen handling, appropriate turn-around time for specimen processing, testing and result reporting, appropriate reference ranges and intelligent result reports

A

Quality Patient Care

53
Q

Probability that a positive test indicates disease

A

Positive Predictive Value

54
Q

Probability that a negative test indicates absence of disease

A

Negative Predictive Value

55
Q

Formula PPV:

A

TP/ TP+FP

56
Q

Formula NPV:

A

TN/TN+FN

Clinical Chemistry (16 decks)

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