A positive Tuberculin skin test is defined as 10 mm or more induration after 48-72 hrs. Usually different technicians are giving Tuberculin Test at the same center. This practice is to be discouraged. It is preferable if one person is designated for giving Tuberculin injection. Similarly one person should be designated to read the Tuberculin Test.
If a patient comes after 72 hrs(upto 7 days) and the reaction is found to be 10 mm or more, then it can be taken as a positive reaction. But if the reaction is found to be less than 10 mm, then it can be repeated on the other forearm.
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