False Positive Result
TST positive is measured by size of induration. The measurement of the induration is determined to be positive depending on risk factors. For example, a low-risk patient must have a larger induration for a positive than a high-risk patient. High-risk groups include recent contact, HIV, chest radiograph with fibrotic changes, organ transplant recipient, and immunosuppression.
According to the Ohio Department of Health and US Department of Health, the BCG vaccine does not protect against TB infection. It does, though, give 80% of children protection against tuberculous meningitis and miliary tuberculosis. Therefore, a positive TST/PPD in a person who received BCG vaccine is interpreted as latent TB infection (LTBI). Due to the test's low specificity, most positive reactions in low-risk individuals are false positives. A false positive result may be caused by nontuberculous mycobacteria or previous administration of BCG vaccine. Prior vaccination with BCG may result in a false-positive result for many years afterwards.
False positives can also occur when the injected area is touched, causing swelling and itching.
Read more about this topic: Mantoux Test
Famous quotes containing the words false, positive and/or result:
“Of what violences, murders, depredations, have not the epic poets, from all antiquity, been the occasion, by propagating false honor, false glory, and false religion?”
—Samuel Richardson (1689–1761)
“I believe, as Maori people do, that children should have more adults in their lives than just their mothers and fathers. Children need more than one or two positive role models. It is in your children’s best interest that you help them cultivate a support system that extends beyond their immediate family.”
—Stephanie Marston (20th century)
“Mothers are likely to have more bad days on the job than most other professionals, considering the hours: round-the-clock, seven days a week, fifty-two weeks a year. . . . You go to work when you’re sick, maybe even clinically depressed, because motherhood is perhaps the only unpaid position where failure to show up can result in arrest.”
—Mary Kay Blakely (20th century)