The patient had some pre-test probability of the disease in question. You did a test and obtained the result "r". This calculator gives the patient's new post-test probability of disease, given that result.

Instructions: Enter parameters in the red cells. Answer will appear in the blue cell.

What is the Pre-Test Probability?	P =		What is the probability (before knowing the test result) that your patient has the disease?
What is the Likelihood Ratio?	LR(r) =		(If you don't know the Likelihood Ratio of the test result, click here and then use the probabilities below to calculate it.)

If you don't know the Likelihood Ratio of the test result:
What is the probability of result r in a patient WITH the disease?	P(r|D+) =
What is the probability of result r in a patient WITHOUT the disease?	P(r|D-) =
	Recalculate LR
Calculated Likelihood Ratio: P(r|D+) / P(r|D-)	LR(r) =	100

Pre-Test Odds = P/(1 - P) = 0.012

Post-Test Odds = Pre-Test Odds * LR(r) = 1.215