Final answer:
A false positive is an incorrect test result indicating the presence of a condition not actually present, often caused by cross-reactivity. False negatives indicate no condition when one is present. Highly sensitive tests minimize false negatives, suggesting a true negative when the test is negative.
Step-by-step explanation:
A false positive is a result that indicates a test subject has a particular infection or condition, such as the presence of an antigen, antibody, or nucleic acid, when in reality, the infection or condition is not present. False positives can have significant implications, especially in medical diagnoses, and can lead to unnecessary stress and additional medical procedures. They commonly occur due to cross-reactivity or similarities in epitopes between different pathogens. For example, if an antibody-based test detects epitopes that are not exclusive to the pathogen in question, it may yield a positive result even though the pathogen is absent. This is why confirmatory tests are often required following a positive screening test result.
A false negative, on the other hand, is the failure to detect an infection or condition when it actually exists. While a false positive could lead to over-treatment, a false negative might result in a lack of treatment, potentially causing the disease to progress untreated. Highly sensitive tests aim to reduce the probability of false negatives, implying that if such a test yields a negative result, there is a high likelihood that the individual is not infected with the pathogen.