Lecture 9 - EBP diagnostic Validity

Question 1

Define Index Test and Reference Standard

Answer 1

Index = the test whose performance is evaluated - lachmans (knee)

Reference = gold standard, the best available against which the test is compared to - X-ray, Ct Scan

Question 2

Assessing bias in Diagnosit Test Accuracy (DTA) has 4 domains

Answer 2

patient selection - random or consecutive
index test - blinded
reference standard - blinded
flow of pts thru study - interval between IT and RS

Question 3

Formula for sensitivity, and what is it good for?

Answer 3

SNOUT

a = true positive
c = false negative
a/a+c

Question 4

formula for specificity and what is it good for?

Answer 4

SPIN

b= false positive
d = true negative 

b/b+d

Question 5

formula for prevalence

Answer 5

a+c/a+b+c+d

Question 6

What is the likelihood ration and how do you interpret it

Answer 6

+ likelihood ratio = how much to increase the probability of the disease given a positive test result - LR+ = sensitivity /(100-specificity)

• likelihood ratio = how much to decrease the probability of the disease given a negative test - LR- = (100-sensitivity) /specificity

Question 7

High Specificity rules IN a condition
High Sensitivity rules OUT a condition
High Lr+ –> increase post-test probability of having the condition given a positive result
Lower LR- –> decreases post-test probability of having the condition

Answer 7

JUST FUCKING KNOW IT