Glossary
Negative Predictive Value
Also called: NPV
The proportion of negative results that are genuinely negative, also dependent on the prevalence of the condition.
NPV answers: this came back negative, how confident can I be. In low-prevalence populations NPV is usually reassuringly high, which is why negative screening results carry real information even from imperfect tests.
Where This Gets Misread
High NPV in a low-prevalence setting is not evidence the model is good. A test that called everything negative would score well on NPV in a rare disease. It is a property of the population as much as of the test.