Analytical and clinical evaluation of methods

Question 1

1. Which statement applies to a sample of values drawn
   from a Gaussian distribution?

a. The central location is best described by the median.
b. The dispersion is best described by the interquartile
range.
c. The distribution of the values is likely to be asymmetric.
d. The t distribution is useful for estimation of the 95% CI for the mean value

Answer 1

d. The t distribution is useful for estimation of the 95% CI for the mean value

Question 2

2. The analytical specificity of an assay is:

a. the ability of an assay procedure to determine the
concentration of a target analyte in the presence of
interfering substances in the sample matrix.
b. the detection limit of a method.
c. the ability of an analytical method to assess small
variations in the concentration of analyte.
d. the analyte concentration range over which measurements are within the declared tolerances for imprecision and bias of the method.

Question 3

3. Two analytical methods are to be compared by analysis in parallel of a suitable number of patient samples. Which of
   the following is correct?

a. Ordinary least-squares regression analysis is the most
appropriate data analysis approach.
b. It is generally recommended that the manufacturer
use 40 samples for comparison and the user laboratory 100 samples.
c. A calibration difference is most typically disclosed by
an intercept estimate significantly different from zero
obtained by regression analysis.
d. In case of constant CV%s, the Bland-Altman difference plot shows an increasing scatter of the measured
differences at increasing measurement values.

Answer 3

d. In case of constant CV%s, the Bland-Altman difference plot shows an increasing scatter of the measured
differences at increasing measurement values.

Question 4

4. In a regression analysis comparing results of two methods, the y-intercept is calculated to be 2.0 and the slope is 3. This indicates a(n):

a. calibration error.
b. uncertainty.
c. systematic difference.
d. interference in one method.

Answer 4

c. systematic difference.

Question 5

5. Which one of the following, when stated as an interval
   around a reported laboratory result, will specify the location of the true value with a given probability?

a. Traceability
b. Coefficient of variation
c. Trueness
d. Uncertainty

Answer 5

d. Uncertainty

Question 6

6. The traceability chain extends downwards from the reference measurement procedure to the routine analytical
   method. Which of the following is correct?

a. A reference measurement procedure is sensitive to
matrix effects.
b. The standard uncertainty indicates a 95% uncertainty
interval.
c. Harmonization of laboratory measurements do not
presuppose traceability to a reference measurement
procedure.
d. The reference measurement procedure is always
more precise than the routine analytical method.

Answer 6

c. Harmonization of laboratory measurements do not
presuppose traceability to a reference measurement
procedure.

Question 7

7. The diagnostic accuracy of a test is assessed on a number of subjects suspected of having a given target disease.
   Which of the following is correct?

a. The diagnostic accuracy is characteristic for the test
and is not influenced by the actual setting in which it
is evaluated.
b. The ROC area provides a measure of the diagnostic
accuracy, which is not dependent on a selected cutoff value.
c. When the cut-off value of a quantitative test is increased,
the specificity declines and the sensitivity increases.
d. In order to rule out the presence of disease, it is important that the specificity is high

Answer 7

b. The ROC area provides a measure of the diagnostic
accuracy, which is not dependent on a selected cutoff value.

Question 8

8. The probability of the presence of a specific disease
   divided by the probability of its absence is the:

a. likelihood ratio.
b. odds ratio.
c. prevalence.
d. predictive value

Answer 8

b. odds ratio.

Question 9

9. When a receiver operating characteristic curve is plotted,
   the x-axis represents the:

a. false-positive rate.
b. true-positive rate.
c. false-negative rate.
d. true-negative rate

Answer 9

a. false-positive rate.

Question 10

10. A new test is added to an existing set of diagnostic procedures. Which of the following is correct?

a. The diagnostic accuracy of the new test is the most
important point to consider.
b. A multivariate data treatment based on logistic regression analysis presupposes quantitative test results.
c. It is unlikely that results from several tests are correlated.
d. The difference between the ROC curve area after addition of the new test and the area of the ROC curve
of the original diagnostic procedure expresses the
added value of the new test.

Answer 10

d. The difference between the ROC curve area after addition of the new test and the area of the ROC curve
of the original diagnostic procedure expresses the
added value of the new test.