Biostats/Epi Week 6 Flashcards
Validity
Ability of a test to distinguish between who has a disease & who does not
Sensitivity
Ability of a test to correctly identify those who DO HAVE a disease
Specificity
Ability of a test to correctly identify those who DO NOT HAVE a disease
Dichotomous results
Yes or no
Does have or does not have
False Positive
Screened positive but does not actually have the disease
False Negative
Screened negative but actually does have the disease
Problems of false positive
$ Brought back for further testing: expensive, possibly invasive
$ Patient anxiety
$ Labeling despite subsequent evaluation as negative
Problems of false negative
$ Serious diseases are not caught & treated as early as possible
Continuous variable testing
Test for which there is no positive or negative & a cutoff point must be marked
Sequential (two-stage) testing
Less expensive/invasive/uncomfortable test first, then more expensive/invasive/uncomfortable for patients who test postive on first test
Net sensitivity
Number of people with disease who tested positive over multiple tests/total number of people in tested group who have disease
Net specificity
Number of people without disease who tested negative/total number of people in tested group who did not have disease
Simultaneous testing
Using two different tests at the same time
Percent agreement
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
Predictive value
Number of true positives/total number who tested positive (true+false positives)
Negative predictive value
Number of true negatives/all those who tested negative (true+false negatives)
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.
Median survival time
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.
Standard life table
What type of analysis is this: Comparison of survival rate for children, ages 8-12, who have experienced closed head trauma.
Relative survival rate
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.
Kaplan Meier life table
Primary care is an intervention that occurs in community based health centers and is primarily considered primary, secondary, or tertiary prevention?
Secondary
The decision whether or not to screen a population for a disease should be based on:
Whether the case-fatality rates will decrease
In order to quantify survival time, the duration of survival is counted from the time of:
Diagnosis
How does case-fatality rate differ from mortality rate?
denominator is the number of individuals who have the disease
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
prevalence and specificity (Gordis Ch 5)
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?
Referral bias
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?
Prognostic selection
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?
Lead time
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?
Over-diagnosis
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.
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).
