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Confused About Results



Hi. I`m a 27 years old lady. I did a PPD at work and it was positive 35mm. Then I did a QTF-gold and the result was negative. My mother told me I had BCG at birth. Please help with these confusing result. Thanks, Regards


The PPD skin test was likely positive because some of the antigens in the PPD cross-reacted with those of the BCG vaccination you received shortly after birth. The blood test for TB that you had, the QTF-gold, uses only 2 or 3 TB antigens, none of which are in the BCG vaccine. The results you describe suggest that you have a false positive TB skin test, and that you are not infected with the TB germ.

You should not ever have another TB skin test (because repeating this would not give any more information in the future). Depending on your job and what state you live in, you may need periodic symptom screening or repeat blood tests for TB in the future. Your employee health advisor or doctor can tell you about the specifics of what screening you need, if any.

For more information:

Go to the Tuberculosis health topic, where you can:

Response by:

Lisa A Haglund, MD Lisa A Haglund, MD
Associate Professor of Clinical Medicine
College of Medicine
University of Cincinnati