# What does positive predictive value tell you?

## What does positive predictive value tell you?

Positive predictive value is the probability that a patient with a positive (abnormal) test result actually has the disease. Negative predictive value is the probability that a person with a negative (normal) test result is truly free of disease.

**What is the difference between positive predictive value and positive likelihood ratio?**

LR is one of the most clinically useful measures. LR shows how much more likely someone is to get a positive test if he/she has the disease, compared with a person without disease. Positive LR is usually a number greater than one and the negative LR ratio usually is smaller than one.

### What is a good PPV and NPV?

Positive predictive value (PPV) and negative predictive value (NPV) are directly related to prevalence and allow you to clinically say how likely it is a patient has a specific disease….Negative predictive value (NPV)

Prevalence | PPV | NPV |
---|---|---|

20% | 69% | 97% |

50% | 90% | 90% |

**How to calculate predictive value and likelihood ratio?**

1. PREDICTIVE VALUE AND LIKELIHOOD RATIO 2. PREDICTIVE VALUE• Predictive value of a positive test result or positive predictive value (PPV) PPV = True positive/ (true positive + false positive)• Predictive value of a negative test result or negative predictive value (NPV) NPV = True negative/ (true negative + false negative) 3.

## What does the positive predictive value (% ) mean?

Positive predictive value (%) defines the probability of the disease in a person who has a positive test result. It represents the proportion of the diseased subjects with a positive test results (TP, true positives) in a total group of subjects with positive test results (TP/(TP+FP)). Therefore,…

**What does a high PV predictive value mean?**

• Predictive value reflects the diagnostic power of a test.• Depends upon sensitivity, specificity and disease prevalence.• A high +PV indicates a strong chance that a person with a positive test has the disease.• A high -PV means that a negative test in effect rules out the disease. 5.

### How is negative predictive value related to diagnostic accuracy?

It indicates the proportion of healthy subjects with negative test results (TN, true negatives) in a total group of subjects with negative test results (TN/ (TN+FN)). Therefore, negative predictive value relates to the predictive ability of a test to identify the absence of the disease in individuals with negative test results.