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;
33 Cards in this Set
- Front
- Back
|
If you are in a systemic inflammatory state, will your ESR be up or down?
|
ESR will be up
|
|
|
If you have an elevated ESR, will RBC settle more slowly or more rapidly?
|
Rapidly
|
|
|
What is the reference group method?
|
Approach to reference range
-Most Common -Specimens collected from random sample of healthy individuals |
|
|
What is the prognosis/treatment-derived method?
|
other approach to reference range determination
-eg. cholesterol Reference ranges set as desirable levels based upon knowledge of what is healthy Could not use central 95% of “normal” population because too many people have unhealthy cholesterol levels |
|
|
what is threshold to diagnose disease
|
something shouldn't normally be there, if it there that is abnormal
ex: CK-MB in serum for dx of acute MI |
|
|
What is a False Positive
|
Falsely identifying a value in a healthy person as being abnormal and representing disease
-where positive=disease |
|
|
What is a False Negative?
|
Falsely identifying an abnormal value in a person with disease as being normal
-where negative=no disease |
|
|
What is specificity of a test?
|
tests what it says it is
|
|
|
When would you want to maximize sensitivity at the cost of specificity?
|
You would want to do this for diseases that are easily treated (so you want to catch 100% of the cases), or very serious diseases (such as HIV)
note that you will see false positives normally there is another secondary tests |
|
|
When do you want to maximize specificity at the cost of some sensitivity?
|
for diseases that are very serious but not curable (such as pancreatic cancer)
this is because the intervention for a person with the disease is quite severe |
|
|
MAKE SURE YOU KNOW THE DIAGRAMS WHERE YOU DRAW THE LINE FOR THRESHOLD (Thus determining specificity/sensitivity)
|
there will probably be a test question on this, so just do me a favor and look up the power point
|
|
|
Define sensitivity
|
ability of tests to correctly identify those WITH disease
|
|
|
Define Specificity
|
Ability of the test to correctly identify those people WITHOUT disease
|
|
|
Accuracy
|
The closeness of the value obtained from a test to the true value
|
|
|
Precision
|
Ability to test one sample repeatedly and obtain the same results; refers to the reproducibility of the test result
|
|
|
On the 4 box chart, what goes on the top axis and what goes on the vertical axis
|
horizontal top: Diseased, Disease-Free
Vertical left: Positive, Negative |
|
|
Describe what goes in A, B, C, D in the 2x2 box
|
A: true positive
B: false positive C: false negative D: true negative |
|
|
How do you calculate sensitivity using a 2x2 box?
|
A
------ x 100 A+C |
|
|
How do you calculate specificity using a 2x2 box?
|
D
-------- x 100 B+D |
|
|
What does A+C show in a 2x2 box?
|
total number of diseased people
|
|
|
what does B+D show in a 2x2 box
|
total number of diseases-free people
|
|
|
If you know that the test sensitivity is 80% for a 50% disease prevalence for 1,000 ppl in a population, what do A and C =?
|
A: 400 (true positive)
C: 100 (false negatives) |
|
|
Make sure you know how to do a 2x2 box
|
go look at the slides
|
|
|
Draw a 2x2 box and label appropriately
|
DO IT NOW!
|
|
|
Do sensitivity and specificity of a test depend on disease prevalence?
|
NO
they are a property of the test itself |
|
|
How do you calculate positive predictive value?
|
go horizontal on the positive portion of the 2x2 box
so PPV= A ------- A+B |
|
|
How do you calculate negative predictive value?
|
go horizontal on the positive portion of the 2x2 box
so PPV= D ------ C+D |
|
|
what is positive predictive value?
|
proportion of those with a positive test who are diseased
|
|
|
what is negative predictive value?
|
proportion of those with a negative test who are disease-free
|
|
|
As the disease prevalence decreases
what happens to the PPV? |
it decreases
|
|
|
As the disease prevalence decreases
what happens to the NPV? |
it increases
|
|
|
What is pretest probability?
|
the likelihood that the patient has a disease (based upon other clinical findings and factors that would suggest likely disease)
|
|
|
not ordering a test if there is little suspicion that the result could be positive is is smart because it would have _____
|
low pretest probability
|
