# http://www.fpnotebook.com/

## Negative Predictive Value

*Aka: Negative Predictive Value*

- See Also
- Screening Test
- Contingency Grid or Cross Tab (includes Statistics Example)
- Bayes Theorem (Bayesian Statistics)
- Fagan Nomogram
- Experimental Error (Experimental Bias)
- Lead-Time Bias
- Length Bias
- Selection Bias (Screening Bias)
- Likelihood Ratio (Positive Likelihood Ratio, Negative Likelihood Ratio)
- Number Needed to Screen (Number Needed to Treat, Absolute Risk Reduction, Relative Risk Reduction)
- Positive Predictive Value
- Pre-Test Odds or Post-Test Odds
- Receiver Operating Characteristic
- Test Sensitivity (False Negative Rate)
- Test Specificity (False Positive Rate)
- U.S. Preventive Services Task Force Recommendations

- Definition
- Patients with negative test that do not have disease
- P(No Disease | negative test )
- Assesses reliability of negative test

- Indications
- Puts Test Sensitivity in context of disease Prevalence
- Lower disease Prevalence results in higher NPV
- Test Sensitivity effect minimized at low Prevalence
- False negatives decrease substantially
- Results in more reliable negative test

- Calculation
- NPV = (True negative) / (true and false negatives)