Deck 5: Establishment and Use of Reference Values

Question 1

An important assumption that is made when using parametric methods to estimate percentiles and their confidence intervals in determining reference limits is that:

A) the type of distribution that the reference values exhibit is a t-distribution.
B) the true distribution that the reference values exhibit is Gaussian.
C) the distribution parameters cannot be estimated.
D) there is no set distribution pattern of reference values.

Answer 1

the true distribution that the reference values exhibit is Gaussian.

Question 2

To determine the confidence intervals of percentiles of ranked data (data arranged by magnitude of value),it is most appropriately assessed using:

A) nonparametric testing.
B) univariate analysis.
C) parametric testing.
D) multivariate analysis.

Answer 2

nonparametric testing.

Question 3

A physician asks your laboratory to begin performing thyroid-stimulating hormone (TSH)analyses on all specimens that have a free thyroxine (FT₄)analysis ordered,a practice that your laboratory currently does not perform.Your laboratory typically performs TSH only on those FT₄ specimens that are outside the population-based reference interval.The physician suggests using subject-based reference intervals,claiming that population-based intervals are clinically insensitive.What is the basis of this claim?

A) Subject-based reference values more closely resemble the group of reference individuals that were used to establish population-based reference intervals.
B) Standardized laboratory methods produce more accurate results when examining individual subject values.
C) Subject-based reference values are more easily tracked and applied in settings in which large numbers of specimens are analyzed.
D) Changes in a subject-based reference value might indicate altered biochemical status yet still be within the population-based healthy reference interval.

Answer 3

Changes in a subject-based reference value might indicate altered biochemical status yet still be within the population-based healthy reference interval.

Question 4

What is the statistical range of the following distribution of data?
21 25 18 20 19 21 23 26

A) 18 to 26
B) 21.6
C) 8
D) .-8

Question 5

Visually inspecting the distribution of reference values can provide a safeguard against misinterpretation of statistical methods,and it may provide valuable information about the data.Which of the following observations might represent erroneous values?

A) Skewed distributions
B) Outlier values
C) Partition criteria
D) Bimodal distributions

Question 6

Even if somewhat impractical,which one of the following preanalytical factors should be standardized when establishing a reference interval for an analyte?

A) Location (building,city,etc.)in which the venipuncture is performed
B) The method of specimen collection
C) Reagents used in analyte analysis
D) The specific method used for analysis

Question 7

The proportion of a population (or of those being tested)with the disease being studied is referred to as the:

A) prevalence.
B) clinical sensitivity.
C) clinical specificity.
D) predictive value.

Question 8

Which one of the following is an example of an exclusion criterion when establishing a healthy population-based reference interval?

A) Use of oral contraceptives
B) Sex
C) Age
D) Ethnicity

Question 9

To reduce workload in your chemistry laboratory,you are setting up a small laboratory on the opposite side of your large city from the main laboratory.When preparing the new laboratory's chemistry analyzer,you decide to use the reference values that have been generated by the main laboratory's chemistry analyzer,which is a larger model (but similar in all other respects)than yours.Can this be justified?

A) No,because each analyzer will produce completely different results from the other laboratory.
B) No,because the populations that will be tested are completely different.
C) Yes,if certain conditions have been fulfilled,such as population matching,data comparison,analytical performance agreement,and specimen standardization.
D) Yes,because you cannot afford to perform reference value determinations in your laboratory.

Question 10

Calculate the clinical sensitivity for the following data: in a group of 80 patients diagnosed with sickle cell disease,72 had positive test results.The clinical sensitivity of this test is:

A) 111%.
B) 100%.
C) 90%.
D) 75%.

Question 11

The results of a certain type of quantity obtained from a single individual or group of individuals corresponding to a stated description is the definition of:

A) reference intervals.
B) reference limits.
C) clinical decision limits.
D) reference values.

Question 12

True negatives ÷ (false positives + true negatives) * 100 is the formula for determining:

A) clinical sensitivity.
B) clinical specificity.
C) analytical sensitivity.
D) analytical specificity.