Final answer:
A negative result on a TST or IGRA test does not necessarily mean a patient is negative for TB due to the possibility of a false negative. Similarly, a positive result does not guarantee active TB due to potential false positives. Both false negatives and false positives must be considered with confirmatory testing for accurate diagnosis.
Step-by-step explanation:
The statement that a negative result to either a TST (Tuberculin Skin Test) or IGRA (Interferon-Gamma Release Assays) test shows that a patient is indeed negative for TB is false. A negative result may occur even when the infection is present, known as a false negative. It is important to consider the probability of Type II error, or β level, which in the context of a TB screening test, if set at 0.20 indicates that there is a 20 percent probability the test will fail to detect TB when it is actually present.
Similarly, a positive result does not necessarily mean that the patient is currently infected with active TB. The false positive scenario is also possible, which occurs when the test mistakenly indicates the presence of TB when it is not present. To account for this, the screening test might have an established Type I error rate, or α level, such as 0.10, which means there is a 10 percent chance of detecting TB when it is not actually present.
Therefore, the accuracy of TB screening tests such as TST and IGRA should always be interpreted with an understanding of the possible false negatives and false positives, in conjunction with other clinical assessments and confirmatory tests.