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.)

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

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

Post-Test Probability = Post-Test Odds/(1 + Post-Test Odds) = 0.548