Which statement about likelihood ratios is true?

Which statement about likelihood ratios is true?

• A. LR+ > 1 indicates decreased odds of disease.
• B. LR- > 1 indicates decreased odds.
• C. LR+ < 1 indicates increased odds.
• D. LR+ > 1 indicates increased odds; LR- < 1 indicates decreased odds.

Answer: (D)

Likelihood ratios show how a test result changes the odds of having the disease. The positive likelihood ratio tells you how much the odds increase when the test is positive, and the negative likelihood ratio tells you how much the odds decrease when the test is negative. By definition, a positive result that truly relates to disease makes LR+ greater than 1, meaning it raises the odds, while a negative result that truly relates to absence of disease makes LR- less than 1, meaning it lowers the odds. So a positive test increases odds (LR+ > 1) and a negative test decreases odds (LR- < 1).

Likelihood ratios show how a test result changes the odds of having the disease. The positive likelihood ratio tells you how much the odds increase when the test is positive, and the negative likelihood ratio tells you how much the odds decrease when the test is negative. By definition, a positive result that truly relates to disease makes LR+ greater than 1, meaning it raises the odds, while a negative result that truly relates to absence of disease makes LR- less than 1, meaning it lowers the odds. So a positive test increases odds (LR+ > 1) and a negative test decreases odds (LR- < 1).