What time frame must the results of the TB test be read within?

The results of a tuberculin skin test (TST), commonly known as a TB test, must be read within 48 to 72 hours after administration. Reading the test within this timeframe is critical because it allows for accurate interpretation of the induration (swelling) that forms around the injection site, which indicates whether an individual may have been exposed to the bacteria that causes tuberculosis.

If the test is read too early (before 48 hours) or too late (after 72 hours), it can result in inaccurate readings that might lead to false negatives or false positives. Therefore, adhering to the 48 to 72 hour window is essential for ensuring proper diagnosis and management of potential TB exposure.