Symptoms of tuberculosis after skin test

TB patients need to inject five units of tuberculin into the flexor side of the forearm and observe the diameter of the local induration 48 to 72 hours after injection. If the induration is between 5 and 9 mm in diameter, it is positive. If the induration is between 10 and 19 mm in diameter, it is moderately positive. If the induration is more than 20 mm in diameter, it is strongly positive.