Quality Control Quiz

Question 1

Which description is not a requirement for QC material?
a) Long –term stability.
b) The matrix is similar to the specimen being tested.
c) The concentration of analytes reflects the clinical range.
d) Analyte concentration must be independent of the method of assay.

Answer 1

d) Analyte concentration must be independent of the method of assay.

Question 2

The process that encompasses all aspects of laboratory operation including patient
identification, specimen collection, equipment maintenance, and the reporting of patient
result is:
a) accuracy
b) reliability
c) quality assurance
d) quality control

Answer 2

c) quality assurance

Question 3

The process that monitors each laboratory analysis, using material with known
constituent concentrations, in order to ensure the accuracy of test result is:
a) pooled control
b) quality assurance
c) quality control
d) accuracy monitoring

Answer 3

c) quality control

Question 4

Which of the following may be used to analyze quality control data?
a) Levy-Jennings plot
b) Westgard rules
c) linearity studies
d) both a) and b)

Answer 4

d) both a) and b)

Question 5

The reproducibility of test measurements is referred to as:
a) accuracy
b) precision
c) quality control
d) reliability

Answer 5

b) precision

Question 6

In Gaussian distribution, the +/- 2SD range includes the following percentage of
values:
a) 31.6
b) 68.3
c) 95.5
d) 99.7

Answer 6

c) 95.5

Question 7

When data fluctuations are due to chance and results are seen to vary in either direction,
the problem is referred to as:
a) the coefficient of variation
b) experimental error
c) random error
d) systematic error

Answer 7

c) random error

Question 8

Inspection of quality control chart can reveal:
a) a shift in the mean
b) a loss of precision
c) the method is out of control
d) the method is in control
e) all of the above

Answer 8

e) all of the above

Question 9

Systematic error in a method would appear on a quality control chart as:
a) increased scattering of points
b) a “trend” upward
c) a shift of the mean
d) would not be detected
e) both b and c

Answer 9

e) both b and c

Question 10

A control serum for glucose analysis has a mean value of 8.3 mmol/L and a coefficient
of variation of 5%. The standard deviation of this method is:
a) 0.42 mmol/L
b) 0.21 mmol/L
c) 5%
d) 2.5%
e) 10%

Answer 10

a) 0.42 mmol/L

Question 11

When standard deviation is expressed as percentage of the mean, this is known as the:
a) standard error
b) average deviation
c) confidence limits
d) coefficient of variation

Answer 11

d) coefficient of variation

Question 12

If the concentration of a standard was labeled incorrectly and the standard was
subsequently used, the quality control chart would probably show:
a) gradual tendency to increased imprecision
b) shift in the mean value
c) increased scatter of results
d) progressive trend toward inaccurate results
e) increased standard deviation

Answer 12

b) shift in the mean value

Question 13

Which of the following conditions is cause for rejecting an analytical run:
a) two consecutive controls greater than 2 SD above or below the mean
b) three consecutive controls greater than 1SD above the mean
c) four controls steadily increasing in value +/-1SD from the mean
d) all of the above

Answer 13

a) two consecutive controls greater than 2 SD above or below the mean

Question 14

Which of the following quality control rules would be broken 1 out of 20 times by
chance alone?
a) 1-2s
b) 2-2s
c) 1-3s
d) 1-4s

Answer 14

a) 1-2s

Question 15

One of two controls within a run is above + 2SD and the other control is below – 2SD
from the mean. What do these results indicate?
a) poor precision has led to random error
b) a systematic error is present
c) proportional error is present
d) QC material is contaminated

Answer 15

a) poor precision has led to random error

Question 16

A trend in QC results is most likely caused by:
a) deterioration of the reagent
b) miscalibration of the instrument
c) improper dilution of standards
d) electronic noise

Answer 16

a) deterioration of the reagent

Question 17

In most circumstances, when two controls within a run are both greater than +/- 2SD
from the mean, what action should be taken first?
a) Recalibrate, then repeat controls followed by randomly selected patient samples if
QC is acceptable
b) Repeat the controls before taking any corrective action
c) Change the reagent lot, then recalibrate
d) Prepare fresh standard then recalibrate

Answer 17

b) Repeat the controls before taking any corrective action

Question 18

When establishing QC limits, which practice below is inappropriate?
a) Using last month’s QC data to determine current targets limits
b) Exclusion of any QC results greater than +/- 2 SD from the mean
c) Using QC results from all the shifts on which the assay is performed
d) Using limits determined by reference laboratories using the same method

Answer 18

b) Exclusion of any QC results greater than +/- 2 SD from the mean

Question 19

Which QC program would provide the most assurance of quality results?
a) IQMH
b) internal QC program with 2 levels of control
c) external QC program with 2 levels of control
d) combination of internal and external QC programs each with 2 levels of control

Answer 19

d) combination of internal and external QC programs each with 2 levels of control

Question 20

The two methods for total cholesterol are compared by running 40 paired patient
samples one time on each instrument. The following results are obtained:
Instrument Mean Standard Deviation
Method x (reference method) 6.14 mmol/L 0.100
Method y (candidate method) 6.40 mmol/L 0.080
Assuming the samples are collected and stored in the same way and the analysis done by a
technologist who is familiar with both methods, what is the bias of the method y?
a) 0.02
b) 1.8
c) 2.6
d) 0.26

Answer 20

d) 0.26

Question 21

Given the following data, calculate the coefficient of variation for glucose:
Analyte Mean Standard Deviation
Glucose 4.26 mmol/L 0.130
a) 3.0%
b) 4.6%
c) 7.6%
d) 33.0%

Answer 21

a) 3.0%