LR+
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
The LR+ (Likelihood Ratio Positive) calculator is a statistical tool that calculates the ratio of the probability of a positive event occurring to the probability of a negative event occurring. It is expressed by the formula Sens/(1-Sp), where Sens is the sensitivity of the test and Sp is the specificity of the test.
This calculator is useful for evaluating the effectiveness of a diagnostic test or a detection strategy. It helps to understand the relationship between the probability of detecting a positive event and the probability of not detecting a negative event.
The LR+ is an important indicator in medical statistics, especially in disease diagnosis. It helps to make informed decisions about the need for a second evaluation or to adopt a different treatment strategy.
It is essential to be careful with the interpretation of the LR+, as it can vary depending on the sensitivity and specificity of the test. Additionally, the LR+ is not an absolute indicator and should be considered in conjunction with other clinical and epidemiological factors to make informed decisions.
Frequently asked questions
What is the sensitivity of a test?
The sensitivity of a test is the probability of a test correctly detecting a positive event. For example, if a test has 90% sensitivity, it means that it will correctly detect 90% of cases of a disease.
What is the specificity of a test?
The specificity of a test is the probability of a test not detecting a negative event. For example, if a test has 95% specificity, it means that it will not incorrectly detect only 5% of cases of a disease that does not exist.
When to use the LR+ calculator?
The LR+ calculator is useful when you need to evaluate the effectiveness of a diagnostic test or a detection strategy. It helps to understand the relationship between the probability of detecting a positive event and the probability of not detecting a negative event.
How to interpret the LR+?
The LR+ must be interpreted in conjunction with other clinical and epidemiological factors. It is not an absolute indicator and may vary depending on the sensitivity and specificity of the test.
What is the difference between LR+ and LR-?
The LR+ (Likelihood Ratio Positive) is the ratio of the probability of a positive event occurring to the probability of a negative event occurring. The LR- (Likelihood Ratio Negative) is the ratio of the probability of a negative event occurring to the probability of a positive event occurring.