EBM

Question 1

Positive likelihood ratio

Answer 1

Sensitivity / (1-Specificity)

Compare the chance of a particular result (+ve or -ve) in diseased people versus the chance of the same result in non diseased people.

Not dependent on prevalence of disease

LR = 1 means test cannot differentiate b/w diseased and non-diseased ppl

LR = 4 means person is 4x more likely to have a positive test result if you have the disease than if you don’t have the disease

Question 2

Negative likelihood ratio

Answer 2

(1-Sensitivity) / Specificity

LR = 0.125 means person is 1/10th more likely to have a negative test result if you have the disease than if you don’t have the disease

Question 3

Likelihood ratio usage

Answer 3

Nomogram to calculate POST-TEST PROBABILITY of disease

Question 4

Pre-test probability

Answer 4

Prevalence of a disease

Question 5

Predictive value

Answer 5

Probability of the test result being correct

Question 6

Positive Predictive Value (PPV)

Answer 6

If a patient has a positive test result, tells the probability of that patient having disease

PPV = TP/TP+FP <= looks at positive test results

Question 7

Negative Predictive Value (NPV)

Answer 7

If a patient has a negative test result, tells the probability of patient not having disease

NPV = TN/TN+FN