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Respiratory Disorders (Expert Forum)
Delayed Reaction to TB test
Answered by
This forum is for questions and support regarding lung and respiratory issues such as: Allergies, Asthma, Bronchitis, Colds - Flu, Chronic Cough, COPD, Cystic Fibrosis, Emphysema, Fibrosis, Lung Abscess, Nasal Polyps, Pleurisy, Pneumonia, Sarcoidosis, Sinusitis, Tuberculosis.
Delayed Reaction to TB test
by Cheryl1234, Apr 11, 2002 12:00AM
Can there be a delayed positive reaction to a Mantoux test, beyond the recommended 48-72 hour recommended wait time? I read that if someone comes in contact with TB then they might have to wait 10-12 weeks afterwards and have another TB test before it reads positive. Is this correct? If a second (re-test) TB test was performed 7 days after the initial TB test and it was positive, does this mean that the person had TB the first time and possibly just misread the results?
Doctor's Answer
by National Jewish, Apr 12, 2002 12:00AM
, Apr 12, 2002 12:00AM
If the tuberculin skin test (PPD) is not read at the recommended time (48 hrs) or there is a questionable reaction after that, the PPD should be repeated. If a person is exposed to someone with active TB the PPD may not be positive immediately. One should wait about 10 to 12 weeks after exposure and repeat the PPD. If the first PPD was read correctly as negative and the repeat 7 days later was read correctly as positive this could indicate a "boosted" effect, which represents an old infection. Please check with your local health department for further recommendations.
