After a Tuberculin Skin Test (TST), healthcare
providers read the test site’s reaction 48 to 72 hours later. They look for a
raised, red bump or swelling at the injection site. The size of this bump is
measured in millimeters. If there’s no bump or it’s less than a certain size
(usually 5-10mm depending on risk factors), the test is considered negative. A
larger bump may indicate a positive result, suggesting potential exposure to
TB. Further evaluation may be needed to confirm active TB infection.