QUALITY ASSURANCE/CONTROL Flashcards

1
Q

Overall program that ensures that the final
results reported by the laboratory are correct

A

Quality Assurance

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2
Q

➔ AKA External Quality Control
➔ Involves proficiency testing
programs
➔ Ex.: National External Quality
Assessment Scheme (NEQAS)

A

Interlab

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2
Q

➔ System of ensuring accuracy and precision in the lab
➔ Process of ensuring that analytical results are correct
➔ QC samples are measured periodically in the same manner as clinical samples

A

Quality Control

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3
Q

➔ AKA Internal Quality Control
➔ Analyses of control samples
together with patient specimens
➔ Important in daily monitoring

A

Intralab

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3
Q

Reagent without any analyte added

A

Reagent Blank

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4
Q

➔ Most specific analytical solution
➔ Value will tell the conc. of the
unknown
➔ Only one analyte

A

Standard

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5
Q

➔ Value will determine accuracy and
precision
➔ Resembles patient sample
➔ Many analyte

A

Control

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5
Q

Indicating a person has the disease when, in fact, he or she does not

A

False positive

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6
Q

-Done on apparently healthy
individuals
-Not a basis for treatment
-Less accurate, less expensive

A

Screening Test

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6
Q

-Done on sick or ill individuals
-Basis for treatment
-More accurate, more expensive

A

Diagnostic Test

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7
Q

Refers to how well the test measures what it is
supposed to measure. It refers to the accuracy of the test, meaning how close the result is to its true value.

A

Validity

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7
Q

Indicating a person has the disease when, in fact, he or she does

A

True positive
(TP)

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8
Q

Refers to how well the test performs in use over time.
It refers to the precision of the test, meaning how close are the results of a test on repetition or how close the
values are from one another.

A

Reliability

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9
Q

Indicating a person has the disease when, in fact, he or she
does not

A

False positive
(FP)

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10
Q

Indicating a person does not have the disease when, in fact, he or she
does

A

False negative
(FN)

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10
Q

Ability of test to detect the smallest amount of
analyte

A

SENSITIVITY

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10
Q

Indicating a person does not have
the disease when, in fact, he or she
does not

A

True negative
(TN)

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10
Q

Ability of test to identify correctly those who
have the disease (a) from all individuals with
the disease (a+c)

A

Diagnostic Sensitivity

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11
Q

Ability of the test to identify correctly those
who do not have the disease (d) from all
individuals free from the disease (b+d)

A

Diagnostic Specificity

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11
Q

Diagnostic Sensitivity formula

A

TPTP + FN

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12
Q

Ability of test to detect substances without
interferences

A

SPECIFICITY

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13
Q

Diagnostic Specificity formula

A

TNTN + FP

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14
Q

Measure of central
tendency

A

Mean

15
Q

Middle value

A

Median

16
Q

Most frequent value

A

Mode

17
Q

Highest value – lowest value

A

Range

17
Q

Measures of dispersion

A

Standard Deviation
and Variance

17
Q

Predictable errors; an error that is constant
when measurements are made under the
same conditions

Causes: deterioration of reagents, improperly
made standard solutions, contaminated
solutions, calibration problems, failing
instrumentation

A

SYSTEMATIC ERRORS

17
Q

Index of precision

A

Coefficient of
Variation

17
Q

Unpredictable errors; often due to instrument,
operator, and environmental conditions

➔ Causes: pipetting error, mislabeling of
samples, temperature fluctuation, improper
mixing of sample and reagent

A

RANDOM ERRORS

17
Q

-is the most
commonly used histogram in QC

➔ A histogram is/are sheets of rectangular
coordinate graphing paper where data for
sequential analysis are plotted to locate the
source of error

A

LEVEY-JENNINGS CHART

18
Q

SYSTEMATIC ERRORS Two types:

A

Constant error & Proportional error

18
Q

is a “multi-rule” system

➔ Developed by Dr. James O. Westgard

➔ Based on statistical concepts which is a
combination of decision criteria or rules to
assess if a system is in control

A

Wesguard Multirule System

19
Q

Violated if the IQC value exceeds the mean by ±2SD

A

12SD

20
Q

Violated if four consecutive IQC values exceed the same limit (mean ± 1SD)

A

41SD

20
Q

Violated when the IQC value exceeds the mean by ±3SD

A

13SD

21
Q

Violated when two consecutive IQC values exceed the
mean on the same side of the mean by ±2SD

A

22SD

22
Q

Violated when one control exceeding the +2s and another exceeding the -2s

A

R4SD

22
Q

➔ AKA Linear or Dynamic Range
➔ Range of analyte concentrations that can be directly measured without dilution,
concentration, or other pretreatment

A

Analytic Measurement Range (AMR)

23
Q

Violated when 10 consecutive IQC values are on the
same side of the mean or target value

A

10x

24
Q

How close the measured value is to the true
value due to systematic error, which can be
either constant or proportional

A

Accuracy

25
Q

Ability of a method to detect small quantities
or small changes in concentrations of an
analyte

A

Analytic Sensitivity

26
Q

➔ Difference between the true value and the
measured value

A

Bias

26
Q

➔ AKA Cross-reactivity
➔ Ability of a method to detect only the analyte it is designed to determine

A

Analytic Specificity

27
Q

➔ Type of systematic error in the sample
direction and magnitude; the magnitude of
change is constant and not dependent on the amount of analyte

A

Constant Error

28
Q

➔ Effect of a compound/s on the accuracy of the detection of a particular analyte

A

Interference

29
Q

➔ Substances that cause interference

A

Interferents

30
Q

➔ Lowest amount of analyte accurately detected
by a method

A

Limit of Detection

31
Q

➔ Lowest amount of analyte that can be
reported while achieving a precision target
(e.g. lowest concentration at which a CV of 10% may be achieved)

A

Limit of Quantitation

31
Q

➔ Type of systematic error where the magnitude changes as a percent of the analyte present, error dependent on analyte concentrations

A

Proportional Error

32
Q

➔ Error varies from sample to sample
➔ Causes include instrument instability,
temperature variations, reagent variation,
handling techniques, and operator variables

A

Random Error

32
Q

➔ Body component (e.g. fluid and urine) in which the analyte is to be measure

A

Matrix

33
Q

➔ Dispersion of repeated measurements about the mean due to analytic error

A

Precision

34
Q

➔ Error always in one direction (may be constant
or proportional

A

Systematic Error

34
Q

➔ Ability of an analytic test to measure a known amount of analyte
◆ A known amount of analyte is added
to real sample matrices

A

Recovery

35
Q

➔ Random error + Systematic error

A

Total Error

35
Q

➔ Refers to the difference between the
measured value and the mean expressed as a number of SDs
➔ An SDI = 0: value is accurate or in 100%
agreement
➔ An SDI = 3: 3 SDs away from the target (mean) and indicates inaccuracy
➔ SDI may be positive or negative

A

Standard Deviation Index