Deck 24: Reference Intervals and Clinical Decision Limits

Question 1

Endocrinologists typically encounter patients with hormonal abnormalities such as Cushing's disease (i.e., hyperadrenocorticism).Which of the following attributes is the most desirable for laboratory tests utilized in this environment?

A)laboratory tests with the highest sensitivity
B)laboratory tests with the highest specificity
C)laboratory tests with the highest predictive value for a positive test
D)laboratory tests with the highest efficiency

Answer 1

laboratory tests with the highest sensitivity

Question 2

Considering normal reference intervals utilized, ______ percent of the time, well (healthy) patients will fall outside this range, and ______ percent of the time, well (healthy) patients will fall within this range.

A)5, 95
B)10, 90
C)15, 85
D)20, 80

Answer 2

5, 95

Question 3

Some medical facilities are known for their cerebrovascular centers that provide immediate care for stroke victims.Which of the following attributes is the most desirable for laboratory tests utilized in this environment?

A)laboratory tests with the highest sensitivity
B)laboratory tests with the highest specificity
C)laboratory tests with the highest predictive value for a positive test
D)laboratory tests with the highest efficiency

Answer 3

laboratory tests with the highest efficiency

Question 4

Which of the following statements correctly compares and contrasts a-priori and a-posteriori methods of reference individual selection?
1)In both methods, exclusion and partitioning take place after sampling and analyte testing.
2)A-priori methods require fewer reference individuals to be studied than a-posteriori methods.
3)Questionnaires for potential reference individuals must be more detailed for a-posteriori methods than for a-priori methods.

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

Question 5

Which of the following laboratory considerations are not necessary factors to consider for the transfer of a reference interval from one laboratory to another?

A)preanalytical considerations
B)analytical considerations
C)postanalytical considerations
D)both a and c

Question 6

In establishing a reference interval, data are plotted on normal-probability paper, and the resulting line curves away from linearity at the upper portion of the plot.What is the next step that should be taken in determining the reference interval?

A)Extrapolate values at the 2.5% and 97.5% levels, and determine the reference interval.
B)Replot data on log-probability paper to straighten the curvature.
C)Omit data associated with the curvature, and use the remaining data to determine the reference interval.
D)Begin the process over, since data cannot be used to determine the reference interval.

Question 7

Which of the following best explains why the phrase reference interval is preferred over the phase normal interval when associated with clinical laboratory test results?

A)The phrase reference interval portrays a more professional image of the clinical laboratory profession.
B)The word normal can be interpreted several different ways in laboratory medicine, resulting in potential confusion.
C)Use of the word normal is coupled with use of the abnormal, which raises objection by many individuals.
D)The phrase reference interval implies that statistical methodology was used to establish the interval.

Question 8

Reference interval determinations should follow the guidelines established by:

A)CDC
B)CMS
C)CLSI
D)IFCC

Question 9

Which of the following best describes the analysis of samples to establish reference intervals for a new laboratory method?

A)Analyze all samples at once, using the same lot of reagent.
B)Have the same technologist analyze the sample to ensure method consistency.
C)Analyze samples without control materials, since results are not reported to the patient.
D)Analyze samples over a period of several days, with several technologists performing the assay with different lots of reagent.

Question 10

Which of the following attributes is the most desirable for a laboratory test utilized in the diagnosis of diseases such as cystic fibrosis that are currently not curable?

A)laboratory tests with the highest sensitivity
B)laboratory tests with the highest specificity
C)laboratory tests with the highest predictive value for a positive test
D)laboratory tests with the highest efficiency

Question 11

It has been shown that significant differences between the standard deviations of subclasses of subjects, even when the means are identical, can lead to deviations in diagnostic sensitivity and diagnostic specificity for disease detection.Thus in these situations, there may be the need for separate reference intervals.What statistical test should be selected to determine the need for different reference intervals in this situation?

A)t-test
B)F-test
C)z-test
D)Dixon's Q

Question 12

To construct receiver-operating characteristic curves, which of the following plots is prepared?

A)specificity versus sensitivity
B)true-negative rate versus false-negative rate
C)false-positive rate versus true-positive rate
D)false-negative rate versus false-positive rate

Question 13

An urologist's office has a high likelihood of encountering patients with prostate cancer.Which of the following attributes is the most desirable for laboratory tests utilized in this environment?

A)laboratory tests with the highest sensitivity
B)laboratory tests with the highest specificity
C)laboratory tests with the highest predictive value for a positive test
D)laboratory tests with the highest efficiency

Question 14

The process of separating reference intervals based on criteria such as age, sex, and race, as well as statistical analysis showing significant differences between these subclasses, is known as:

A)partitioning
B)transference
C)diagnostic specificity
D)diagnostic sensitivity

Question 15

Which of the following steps should be taken when an outlier value is obtained during data collection for the determination of reference intervals?

A)The outlier value should be dropped without further consideration.
B)The outlier value indicates a problem with the sample group; it must be redefined and the process started over.
C)The outlier value indicates a problem with the new procedure being implemented; it must be corrected before the samples are reanalyzed.
D)The outlier value should be further evaluated to determine whether it should be included with or deleted from data used to determine the reference range.

Question 16

CLSI guidelines recommend that the reference interval be estimated by the nonparametric method and that a minimum of _______ reference values be utilized for reference-interval determination.

A)75
B)120
C)200
D)300