Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
24 Cards in this Set
- Front
- Back
|
Define Likelihood ratio (for a pos test):
|
How many times more/less likely a pos test result is found in a diseased vs nondiseased patient.
|
|
|
Formula for pos LR:
|
Sensitivity
----------- 1 - Spcfity |
|
|
Formula for neg LR:
|
1-Sens
------ Sp |
|
|
Define negative LR:
|
How many times more/less likely a neg test result is found in a nondiseased as compared to a diseased individual.
|
|
|
Formula for post-test odds:
|
Pretest Odds x Likelihood Ratio
|
|
|
what is the formula for pre-test odds?
|
Prev
----- 1-Prev |
|
|
So if a disease prevalence is 60% what are the odds of having the disease?
|
60:40
|
|
|
What does likelihood ratio do for interpreting Diagnostic testing?
|
Moves the estimated odds (probability) toward either end of the scale.
|
|
|
What is the tradeoff of increasing a test's sensitivity?
|
It will be accompanied by a decrease in specificity.
|
|
|
What feature of a ROC curve will show a most accurate test?
|
the closer the curve comes to the upper left corner of the roc space
|
|
|
What happens as the Roc curve comes closer to the 45-degree diagonal of the roc space?
|
The less accurate the test is.
|
|
|
So a worthless ROC curve is:
|
a STRAIGHT DIAGONAL LINE
|
|
|
What represents the likelihood ratio on a ROC curve?
|
The slope of the tangent line at a given cutpoint.
|
|
|
What will give the highest LR?
|
The steepest slope
|
|
|
What does the area under the ROC curve represent?
|
Test accuracy
|
|
|
4 types of bias in diagnostic testing:
|
-Spectrum bias
-Lead-time bias -Length-time bias -Workup bias |
|
|
What is Spectrum bias?
|
When the study population has a higher disease prevalence than typical populations.
|
|
|
What is LeadTime Bias?
|
When detecting a disease earlier appears to increase survival duration but it's false.
|
|
|
What is length time bias?
|
When screening is more likely to catch lengthy cases because they are chronic and less rapidly fatal.
|
|
|
What is Workup bias?
|
When patients with pos or neg test results are preferentially referred to recieve verification of diagnosis by the gold standrd
|
|
|
Why is lead time bias not truly an increased survival duration?
|
Because the patient still dies at the same time, just knows they are diseased for a longer period of time.
|
|
|
If a screening test detects many more slow than rapidly growing tumors what type of bias is it?
|
Length time bias.
|
|
|
What is the 1st level of the Hierarchical model for diagnostic technology assessment?
|
Technical quality of the test - ie image quality, lab test reproducability.
|
|
|
What is the 2nd level of the Hierarchical model for diagnostic technology assessment?
|
Diagnostic accuracy of the test
-sensitivity -specificity |
