Deck 25: Quality Control for the Clinical Chemistry Laboratory

Question 1

Which of the following mechanisms utilized by clinical laboratories will help detect misidentification of an individual patient specimen?

A)quality-control procedures
B)autoverification
C)comparison with reference intervals
D)delta checks

Answer 1

delta checks

Question 2

Westgard control rules utilize a shorthand system in which the first designation indicates _____, and the second designation, usually subscripted, indicates ______.

A)the number of observations to be considered, the acceptable limits
B)the number of observations to be considered, the probability of false rejection at that number of observations
C)the allowable error before the run is rejected, the acceptable limits
D)the allowable error before the run is rejected, the probability of false rejection at that level of error

Answer 2

the number of observations to be considered, the acceptable limits

Question 3

Which of the following statements are correct regarding controls and calibrators?
1)Controls may not be used as calibrators.
2)Calibrators may not be used as controls.
3)Controls establish correspondence of instrument output signal with known concentration.
4)Calibrators establish correspondence of instrument output signal with known concentration.

A)2, 4
B)1, 3
C)2, 3
D)1, 4

Answer 3

1, 4

Question 4

Suppose a laboratory expands its acceptable limits for quality-control results from 0 ± 2ₛ to 0 ± 2.5ₛ.What is the potential negative aspect of this change?

A)There may not be sufficient error detection.
B)There may be too many false rejections of acceptable test results.
C)The control limits for rejecting an analytical run will become too narrow.
D)There will be improved detection of method failure.

Question 5

A reference method is:

A)the most commonly used method.
B)the scientifically most accurate method.
C)a method that can be used for qualitative screening only.
D)a method that has demonstrated similar but slightly less accuracy than a definitive method.

Question 6

The most common graphical plot used as a visual tool for evaluating quality-control data is the:

A)Gaussian distribution
B)Levey-Jennings plot
C)cusum plot
D)Tonks-Youden plot

Question 7

Autoverification is a software system that is designed to:

A)use patient data to alert technologists that a method may be out of control.
B)use quality-control data to alert technologists that a method may be out of control.
C)verify the correct identification of patient samples used in the laboratory.
D)assure that pre- and postanalytical sources of error are maintained at a minimum.

Question 8

Violation of which of the following Westgard control rules would be associated with the greatest degree of imprecision?

A)12ₛ
B)22ₛ
C)R4ₛ
D)1q

Question 9

A field method is:

A)the most commonly used method.
B)the scientifically most accurate method.
C)a method that can be used for qualitative screening only.
D)a method that has demonstrated similar but slightly less accuracy than a definitive method.

Question 10

Suppose a test procedure has been determined to be out of control.What is the first step that should be taken by the technologist to correct the problem?

A)recalibrate the instrument
B)retest using fresh aliquots of control materials
C)replace reagents
D)perform instrument maintenance

Question 11

Which of the following would likely not be detected by quality-control procedures in a laboratory assay performed manually?

A)deteriorated reagent
B)improper reaction temperature
C)pipetting error
D)spectrophotometer set at the wrong wavelength

Question 12

A definitive method is:

A)the most commonly used method.
B)the scientifically most accurate method.
C)a method that can be used for qualitative screening only.
D)a method that has demonstrated similar but slightly less accuracy than a reference method.

Question 13

A delta check is a check of the difference between:

A)two consecutive control observations
B)the mean of the control material and the control value observed
C)two consecutive measurements of the same analyte on the same patient
D)the mean of the normal reference interval for the analyte and the patient result

Question 14

An abrupt and sustained change of control values in one direction is known as a ______, and a gradual change of control values in one direction is known as a ______.

A)random error, trend
B)trend, shift
C)shift, trend
D)shift, random error

Question 15

Utilizing 95% confidence limits for quality-control materials, one would expect how many valid quality-control test results to fall outside the established limits?

A)one in 95
B)one in 5
C)one in 10
D)one in 20

Question 16

Which of the following are CLIA '88 requirements for the use of quality-control materials?
1)At least two control samples of different concentrations must be tested every 24 hours.
2)At least one blood-gas control sample must be tested every 8 hours.
3)Both high and low blood-gas control materials must be tested every 24 hours.
4)At least one calibrator or control must be tested each time a patient sample is tested.

A)1, 2, 3, 4
B)1, 2, 4
C)1, 3, 4
D)1, 3