Midterm - research studies on diagnostic procedures Flashcards
The extent to which an examiner can measure multiple times and achieve the same results (You X 5)
Intra-examiner reliability
The extent to which multiple examiners can perform same measure on the same person and come up with same results (5 different people)
Inter-examiner reliability
How often does the test yield the same result on a diseased person?
Test reliability
How often does the test achieve the same outcome when multiple measures on the same patient is achieved
test-retest reliability
What is a measure of dichotomous variables’ agreement above chance alone and is used to measure reliability? Used when outcome is binary (yes/no. Positive/negative)
Kappa (K)
What is a reliable Kappa statistic?
Depends on what it is associated with. 0.61+ for manipulative therapy. 0.80 for others
What state is used when there are categorical (e.g. grade 1, 2, 3) or continuous variables (scale of 0-20)
Intra-class correlation (ICC)
What is the ability of a test to correctly identify people who have the target disorder?
Sensitivity
What is the ability of a test to correctly identify people who do NOT have the target disorder?
Specificity
What kind of table or graph do you calculate sensitivity and specificity?
Contingency table
What are true positives?
Those who test positive and have the disease
What are true negatives?
Those who test negative and do NOT have the disease
What are false positives?
Those who test positive for the disease but do NOT have the disease
What are false negatives?
Those who test negative for the disease but DO have the disease
We want screening tests to be extremely __________ while we want confirming diagnosis tests too be highly __________
sensitive
specific
How do you use +SPin and -SNout
SPecificity to rule something IN with + tests
SeNsitivity to rule something OUT with - tests
How do you calculate sensitivity and specificity
SeNsitivity: true pos divided by (true pos + false neg)
SPecificity: true neg divided by (false pos + true neg)
What is a derivation of sensitivity and specificity that takes into account how impactful false pos and false neg components of the test’s performance are in being able to “trust” the outcome of a test.
Predictive value
this is a step up from sensitivity and specificity alone
What is a positive predictive value
Probability that the disease is present when the test is positive
What is a negative predictive value
Probability that the disease is NOT present when the test is negative
What indicates the change in odds that a patient has (or does not have) a particular condition based on whether a test is positive or negative
Likelihood ratios
Tell me how likelihood ratios work
Ok, your turn is over. My turn.
It starts with a baseline probability that a person has a disease.
That place is called perfectly uncertain and it is based on established rates of that condition in society or that subset of the population.
Then you run a test.
With each new test, you move the probability ticker mark from where it was at baseline to the right or the left.
More specifically you move it up or down the probability scale toward exclusion threshold or the therapy threshold.
What are the formulas for likelihood ratios
+LR = sensitivity divided by (1-specificity)
-LR = (1-sensitivity) divided by specificity
What does a LR of 1.0 mean
No impact point
everything above that is a +LR and everything below is a -LR
What is the 15/30/45 rule in regards to the magnitude of +/- LR
when a +LR = 2.0 you say that: a positive test with +LR = 5.0 increases the post-test probability that the patient has the disease by ↑15%
+5 = ↑30%
+10 = ↑45%
