I got a tb/ppd test on monday, and got my test read on wednesday, but the results were negative and didn't see a sign of a reaction that day. that thursday, i saw that i had what look like a bruise. is there any way that it was a mistake, and i actua?

About PPD tests: A PPD skin test reaction is read between 48 and 72 hours after administration. The reaction should be measured in millimeters. The part that is measured is the induration (palpable, raised, firm area or swelling). If there is no raised skin that one can FEEL without looking at it, then there is nothing to measure (the result gets written as 0 mm). Each patient's situational details also matter.