Biostats/Epi Week 6

Question 1

Validity

Answer 1

Ability of a test to distinguish between who has a disease & who does not

Question 2

Sensitivity

Answer 2

Ability of a test to correctly identify those who DO HAVE a disease

Question 3

Specificity

Answer 3

Ability of a test to correctly identify those who DO NOT HAVE a disease

Question 4

Dichotomous results

Answer 4

Yes or no

Does have or does not have

Question 5

False Positive

Answer 5

Screened positive but does not actually have the disease

Question 6

False Negative

Answer 6

Screened negative but actually does have the disease

Question 7

Problems of false positive

Answer 7

$ Brought back for further testing: expensive, possibly invasive
$ Patient anxiety
$ Labeling despite subsequent evaluation as negative

Question 8

Problems of false negative

Answer 8

$ Serious diseases are not caught & treated as early as possible

Question 9

Continuous variable testing

Answer 9

Test for which there is no positive or negative & a cutoff point must be marked

Question 10

Sequential (two-stage) testing

Answer 10

Less expensive/invasive/uncomfortable test first, then more expensive/invasive/uncomfortable for patients who test postive on first test

Question 11

Net sensitivity

Answer 11

Number of people with disease who tested positive over multiple tests/total number of people in tested group who have disease

Question 12

Net specificity

Answer 12

Number of people without disease who tested negative/total number of people in tested group who did not have disease

Question 13

Simultaneous testing

Answer 13

Using two different tests at the same time

Question 14

Percent agreement

Answer 14

Add the numbers in all cells which have agreement by both observers/divide that sum by total number of results read, then multiply by 100 to get percentage

Question 15

Predictive value

Answer 15

Number of true positives/total number who tested positive (true+false positives)

Question 16

Negative predictive value

Answer 16

Number of true negatives/all those who tested negative (true+false negatives)

Question 17

What type of analysis is this: comparison at the end of a study investigating the effectiveness of treatment for multiple myeloma by examining the survival rates for one-half of the population.

Answer 17

Median survival time

Question 18

What type of analysis is this: Comparison of survival each year within two large randomized control clinical studies investigating African American males with Hypertension. One group receives an ACEI and one group receives a Ca Channel Blocker. Loss to treatment occurred each year of the 5 year study.

Answer 18

Standard life table

Question 19

What type of analysis is this: Comparison of survival rate for children, ages 8-12, who have experienced closed head trauma.

Answer 19

Relative survival rate

Question 20

What type of analysis is this: Comparison of a small group of women, ages 45-55, receiving a new treatment for endometrial cancer. The researcher wants to know the cumulative proportion surviving to the end of the study.

Answer 20

Kaplan Meier life table

Question 21

Primary care is an intervention that occurs in community based health centers and is primarily considered primary, secondary, or tertiary prevention?

Answer 21

Secondary

Question 22

The decision whether or not to screen a population for a disease should be based on:

Answer 22

Whether the case-fatality rates will decrease

Question 23

In order to quantify survival time, the duration of survival is counted from the time of:

Answer 23

Diagnosis

Question 24

How does case-fatality rate differ from mortality rate?

Answer 24

denominator is the number of individuals who have the disease

Question 25

Health care providers create a clinical diagnosis, but order tests to confirm the suspected disease. To predict the value of the test when the disease is infrequent, the two factors to consider are

Answer 25

prevalence and specificity (Gordis Ch 5)

Question 26

In a test evaluating a new dieting program, participants who were lost to follow up were not included in the statistical results. What type of bias is this?

Answer 26

Referral bias

Question 27

Decreased all-cause mortaliy rates in a non-randomized trial evaluating the effect of Treatment B in adult white females in suburban America. What type of bias does this show?

Answer 27

Prognostic selection

Question 28

In reviewing the raw statistics, the screening for Disease A increased survival time. No additional years of survival was attained. What type of bias does this show?

Answer 28

Lead time

Question 29

Reduction in occurrances of stroke through early identification of TIAs with use of a CT scan with contrast of brain. What type of bias does this show?

Answer 29

Over-diagnosis

Question 30

NAATs (DNA tests) may not be useful for conducting studies of susceptibility to Chlamydia trachoma re-infection or test-of-cure because a positive NAAT result could reflect a variety of states and conditions, including remnants of DNA from a previous infection. This knowledge will result in a change in practice because the ­­­­­­­­­­­­­­­­­­­­­___________ of NAATs in test-of-cure cases is uncertain.

Answer 30

validity. Gordis, Chapter 5, p. 86. Validity is a test is defined as the ability to distinguish between those who have a disease and those who do not. In this case, the re-test may detect remaining DNA, identifying the person who is treated and not now infected, but still carries the DNA for the dead Chlamydia trachoma. Therefore, the CT test-of-cure must be a culture! (because the re-test NAAT is not valid).