Does redness indicate a positive tuberculosis test?
Redness alone does not mean a positive result. This is a negative result. There must be an induration (raised bump) that is hard and surrounded by redness. If there is an induration, it will be measured. If it is 5mm or greater in diameter, it’s considered a positive. But this doesn’t necessarily mean that there is active TB or there has been exposure to TB. There are other conditions that can give a false-positive. Current therapy with prednisone, for example, can give a false-positive reading. If there’s no existing and known condition to explain the false-positive, this would have to be followed up with a chest X-ray to confirm or deny active (requires a sputum culture) or past exposure. If this were the case, no further testing is done. There will always be a postive reading. Chest X-rays will be done instead.
