For quantitative testing of most analytes, at least how many levels of control must be analyzed?
A) two
Which of the following Westgard rule violations suggests a significant increase in random error.
D) 1-3s
Which of the following Westgard rules requires evaluation of data from previous control measurements?
D) 4-1s
The set of rules regulating the performance of clinical laboratory testing are provided by:
A) All of the above
If a test system has shifted such that control results are now 2 sd above the target mean, the probability that a repeat test will be below the +2 sd limit is:
A) 50.0%
Method comparison should include all of the following EXCEPT:
C) testing done on a single day
Method validation of a moderately complex test, by national regulations, must include verification of the following EXCEPT:
A) all of the above are required
Method evaluation (vs validation) involves
E) 1 and 2
An example of an external quality control program is
C) proficiency testing
In good quality control programs, it is desirable to have a high probability rate for
B) error detection
(T/F) A violation of the R4SWestgard rule means that 2 controls within a run exceed the same 4s limit, and is indicative of increased random error.
False
(T/F) Random QC errors are indicators of increased imprecision and result in a widening of the control distribution.
True
A gradual increase or decrease in the values obtained in quality control analysis is termed a
B) trend
Which of the following Westgard rules is primarily sensitive to systematic error in the test system?
C) 2-2s
Pick the best answer regarding the Westgard Multirulesystem.
D) all of these
(T/F) The delta check was primarily designed for detecting specimen labeling errors.
True
Briefly describe two differences between quality control and quality assessment. Possible comparisons: when are they performed and what are they detecting?
Quality control is (at least) a daily "check" to see if the instrumentation is CURRENTLY accurate and precise. It allows us to validate a run of patient results.
Quality assessment is a less frequent review of all procedures and results to determine what can be improved to minimize error and increase both accuracy and precision. It may be in response to a problem and how to avoid that problem in the future.
The fewest errors occur in which phase of laboratory testing.
D) analytical
An abrupt change in control results which establishes a new pattern above or below an established mean is termed a(n):
A) shift
Hemolysis is a common interference in chemistry tests. For 2 points, briefly describe mechanisms (up to 3) for how this occurs. 1 point extra credit possible.
Spectral hemolysis can cause interference at 3 different absorption wavelengths, often causing false positives for a sample.
Chemical enzymes contained within the RBC may use analyte as substrate, and may cause a false negative result
Addition analytes trapped within the RBC may be released causing an artificial increase to the measured analyte of interest
Which of the following is the calculation for coefficient of variation (CV)?
D) CV = (standard deviation ÷ mean) × 100%
Two types of error may be encountered during analysis of a substance. The type of error that occurs with a constant or predictable difference or trend, either positive or negative, and thus is related to bias, is best described as a(n) _____ error.
A) systematic
(T/F) A correlation coefficient (r value) of >0.95 between two analytical methods indicates acceptable agreement and that they give comparable results.
False
(T/F) Per national regulations, verification of a manufacturer's published reference interval requires testing of at least 120 "normal" patients.
False
For today's glucose QC, the abnormal control is >2s below the mean. Upon examination of prior runs, you notice that the last four abnormal control values are all >1 s (standard deviation) below the target mean. The test was last calibrated one week ago. Of the listed issues, the most likely cause of this scenario would be:
B) reagent deterioration
Which of the following scenarios would most likely yield an increase in random error?
D) incomplete cuvette washing
+Sensitivity
+Specificity
+Predictive value of a positive result
+Predictive value of a negative result
-The fraction of test results that correctly define healthy or diseased patients
-The fraction of positive test results that are from diseased patients
-The fraction of diseased patients detected by the test
-The fraction of patients tested that have the disease being tested for
-The fraction of diseased patients detected by the test
-The fraction of healthy patients that have a negative test result
Sensitivity: The fraction of diseased patients detected by the test
Specificity: The fraction of healthy patients that have a negative test result
Predictive value of a positive result: The fraction of positive test results that are from diseased patients
Predictive value of a negative result: The fraction of negative test results
For each aspect of the testing process on the left, match to its corresponding place on the right:
To determine (im)precision for an assay, you would:
C) Perform replicate testing of a sample with the analyte and calculate the standard deviation
(T/F) In proficiency testing required by national regulations, sets of 5 samples are distributed and tested 3 times per year. To pass each analyte, 4 of each challenge's results must be within the acceptable range.
True
For each clinical scenario, what type of QC error type are you most likely to see:
+Deteriorated calibrator
+Cuvet incubator heater failure
+Failed mixer motor
-Random
-Systematic
-Mixed
-Unlikely to cause error
Deteriorated calibrator: Systematic
Cuvet incubator heater failure: systematic
Failed mixer motor: Random
The LeveyJenningsmethod of QC, using 2 levels of controls for a test, has a false rejection rate of:
B) 9.0%
Number the five steps of Total Quality Management as presented in class in order of performance
Quality Improvement
Quality Control
Quality Assessment
Quality Processes
Quality Planning
Quality Assessment
Quality Control
Quality Improvement
Quality Planning
Quality Processes
As you start your shift, you are told by the preceding shift that both controls on the automated glucose assay were >3 sd above their respective means and they didn't have time to troubleshoot. The most likely cause of this failure is:
B) calibrator problem
When introducing an FDAapprovedmoderate complexity test to the laboratory, you must determine or verify you meet the manufacturer's performance characteristics for all the following EXCEPT:
A) analytical sensitivity
A control has a target mean of 100 mg/dL and a target sd of 4 mg/dL. Today's result for that control is 110 mg/dL. Calculate the z value:
C) +2.5
A sample drawn from the same arm as a D5W IV would likely have a(n) [direction] in the observed result for the following serum tests.
+glucose
+sodium
-decrease
-increase
-no change
glucose: increase
sodium: decrease
Adding a known amount of analyte to a sample and and assaying to determine a parameter of assay quality in method validation is known as:
A) recovery
QC for an automated glucose assay gives a 22swithinrun (across control) error. Review of previous results show no patterns of note. Review of records show that a new lot of reagent was received last week and today was its first use. The LEAST reasonable response would be to
C) rerun the controls
In a reference interval determination, you see that the distribution of patient results is not Gaussian, but skewed to the high side. To define a reference interval for this test, you could (multiple answers possible)
a) discard the high samples as likely outliers
b) use non-parametric statistics
c) still use the mean +- 2sd
d) not supply a reference interval
e) mathematically transform the patient data
