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A 34-year-old member asked:

What does it mean if i have a negative tb skin test yet a positive blood one?

1 doctor answer3 doctors weighed in
Dr. Lois Freisleben-Cook
Pediatrics 41 years experience
IMMUNE PROBLEM: Both tests detect prior exposure to TB. A situation of diminished immune function, called anergy, can make the skin test appear negative. If you have a positive blood test you will need to have a CXR to exclude active infection and may need prophylaxis .

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A 40-year-old member asked:

Could a positive TB skin test mean you always have tb?

1 doctor answer2 doctors weighed in
Dr. Nela Cordero
Pediatrics 54 years experience
POSITIVE PPD: NO. Sometimes it is due to immunization given before. Take a chest x-Ray to find any lesion in the lungs.
Dr. Michael Fisher
Dermatology 32 years experience
Quantiferon TB Gold Test is more accurate Than the skin test. Requires a single patient visit to draw a blood sample. Results can be available within 24 hours. Does not boost responses measured by subsequent tests, which can happen with tuberculin skin tests (TST). Is not subject to reader bias that can occur with TST. Is not affected by prior BCG (bacille Calmette- Guérin) vaccination.
Jun 17, 2014

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Last updated May 10, 2018

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