Deck 11: Quality Control

Question 1

Which of the following is true regarding proportional systematic errors?

A) The slope and the x-intercept of the regression line are affected.
B) The slope of the regression line differs from the true value.
C) The x-intercept of the regression line becomes equal to the y-intercept.
D) The y-intercept of the regression line differs from the true value.

Answer 1

The slope of the regression line differs from the true value.

Question 2

An automated cell counter consistently produces red blood cell readings that are 20% too low.What type of error is this considered?

A) Absolute
B) Random
C) Systematic
D) Variable

Answer 2

Systematic

Question 3

Using only the 1₃s rule to evaluate a control run has a low risk of falsely rejecting a run.What is a common concern about using only this rule?

A) The frequency of acceptable rejection is 25%.
B) The number of random errors is high.
C) The rate of error detection is low.
D) The rule cannot detect a systemic error.

Answer 3

The rate of error detection is low.

Question 4

The following is a Levey-Jennings chart.
Which of the following is the best conclusion based on the circled data?

A) The data fall within 2 SD of the mean; so the recent run can be accepted.
B) The data have several outliers; so the recent run must be rejected.
C) The data comply with at least 3 of the Westgard Rules; so the recent run may be accepted.
D) The data violate the Westgard Rule of 10ₓ; so the recent run must be rejected.

Question 5

A Levey-Jennings chart is created to analyze a set of data.The last consecutive eight data points gradually move downward away from the mean.What type of aberration would this be considered?

A) Outlier
B) Shift
C) Trend
D) Variance

Question 6

What is a concern about the single rule that dictates that control values must fall within two standard deviations of the mean?

A) It can only be trusted when greater than ten different controls have been tested.
B) It can trigger false alarms that cause rejection of acceptable runs.
C) It is insufficient to detect errors created by compromised controls.
D) It is only applicable to instruments previously calibrated by the International Standards Committee.

Question 7

How can the effects of random error be minimized?

A) By averaging a large number of results
B) By having all tests performed by the same technician
C) By multiplying the results by a constant standard
D) By performing control tests in a fixed environment

Question 8

The following is a Levey-Jennings chart measuring a single control.
What Westgard Rule is violated in this chart?

A) Rule 1₂s
B) Rule 1₃s
C) Rule 2₂s
D) Rule R₄s

Question 9

Which of the following explains how a violation of Westgard Rule R₄s is identified?

A) The difference between two consecutive data points is at least 4 SD, and one data point lies
above and the other lies below https://storage.examlex.com/TB34225555/.

B) The result from 2 single control run lies outside the range

C) The result from one control lies above and the result from a different control lies
below

D) Both A and C are correct.

Question 10

Which of the following is true regarding constant systematic errors?

A) The slope and the x-intercept of the regression line are affected.
B) The slope of the regression line differs from the true value.
C) The x-intercept of the regression line becomes equal to the y-intercept.
D) The y-intercept of the regression line differs from the true value.

Question 11

One of three quality-control results for an instrument violates the 1₂s rule.What is the proper course of action?

A) Continue to run samples but mark the results as "pending QC approval."
B) Use a back-up instrument for running patient specimens until resolution of the problem.
C) Refrain from running patient specimens until resolution of the problem.
D) Because the 1₂s rule is only a warning, continue running patient specimens.

Question 12

Which of the following is a crucial feature of a substance used as a control?

A) It should be constructed from real human tissues or fluids.
B) It should be provided and maintained by the manufacturer of the assay or equipment.
C) It should be stored at 32°C to prevent degradation.
D) It should mimic the chemical and physical properties of a typical patient specimen.

Question 13

Which of the following is true about Rule 1₂s?

A) A control violates the rule only when it falls more than 3 SD from the mean.
B) A control that deviates up to -4 SD from the mean is not considered in violation.
C) A control will violate the rule approximately once in every 20 acceptable runs.
D) A violation of this rule should result in rejection of the recent runs.

Question 14

What are the rules,as stated by CLIA,for the number and frequency of control tests that a laboratory should run on a qualitative assay?

A) A test of one positive and one negative control must be run at least once per day.
B) A test of three controls at unknown concentrations must be run at least twice per day.
C) A test of two controls at different concentrations must be run at least once per day.
D) A test of two different positive controls must be run at least twice per day.

Question 15

Many laboratories have the policy that,in the event of a Rule 1₂s violation,the control must be repeated.If the result is in range,then patient specimens may be run.Why is this common practice controversial?

A) It circumvents the absolute rejection rule where any rule violation automatically results in rejection.
B) It does not follow the standard procedure of verifying a rejection under a single rule using multirule tests.
C) It supplants an internal quality-control procedure that was designed specifically to minimize the rate of false rejection.
D) All of the above.

Question 16

The following plot is a Levey-Jennings chart.
Which of the following is true about the data point noted by the arrow?

A) It indicates a shift has occurred.
B) It is an outlier.
C) It suggests the data are trending downward.
D) None of the above

Question 17

Which of the following explains the primary use of Levey-Jennings charts?

A) Determination of the best fit line through a large set of data points
B) Generation of a standard curve from which information about a sample, such as concentration, can be determined
C) Identification of outliers, trends, and shifts in data that may indicate a malfunction or other problem
D) Maintenance of laboratory equipment in compliance with the International Sensitivity Index (ISI)

Question 18

On a Levey-Jennings chart,the final single data point falls outside the +3 SD mark.According to Westgard Rule 1₃s,should the most recent run be accepted?

A) No, because any data point that does not exactly equal the mean value must be rejected.
B) No, because the data point falls outside the accepted range of
C) Yes, because runs are rejected only if six or more consecutive data points deviate by greater than +3 SD from the mean.
D) Yes, because values that fall beyond positive standard deviations from the mean are still within the acceptable range.