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Why can a laboratory test produce a false-positive or false-negative result?
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blood analysis
The physical and chemical properties of a sample of blood are examined during blood analysis. The examination of blood is important for the accurate diagnosis of disease.
In the context of blood analysis and other clinical testing, false-positive and false-negative results occur due to the inherent limitations of a test's sensitivity and specificity.
- False-negative results occur when a test incorrectly categorizes an individual as not having a condition when they actually do. This is related to a test's sensitivity, which measures how well a test identifies the presence of a disease or trait. A test with lower sensitivity is more likely to miss cases, resulting in false negatives.1
- False-positive results occur when a test incorrectly categorizes an individual as having a condition when they do not. This is related to a test's specificity, which measures how well a test identifies the absence of a condition. A test with lower specificity is more likely to incorrectly flag healthy individuals, resulting in false positives.1
These outcomes are often a trade-off in screening tests, which are used for their practicality, speed, or safety compared to definitive diagnostic tests. The predictive value of a result depends on both these statistical measures and the underlying prevalence of the condition in the population being tested.1