Doctor insights on:
False Positive Tb Test
Mycobacterium tuberculosis is an infectious organism that spreads by droplets coughed out by an infected person. Infection is established initially in lungs, but can spread within lungs & to other body parts, or can become latent, with reactivation occurring years to decades later. With effective treatment, it can be completely eliminated although drug resistant ...Read more
My 9-year-old cousin has had a terrible cough for several months. False positive on TB test, physician dismissed the issue. What else should we do?
If a person had TB as child and underwent treatment for it, could he have a false positive TB skin test as an adult?
Can DPT booster done at the same time affect TB test so that it is interpreted as false positive? In addition, TB test site bled right after injection
PPD: First- DTP injection does not affect the response to TB test second- TB test is placed intra dermally - which means no bleeding at injection site. ...Read more
Usually unknown: The reasons for false positive PPD are unknown. There is speculation that it could sometimes result from past infections with various TB-like bacteria. Such infections aren't very common, but they are equally frequent in the Netherlands as anywhere else. As long as the tested person is outwardly healthy and definitely does not have tuberculosis, this is nothing to worry about. ...Read more
Easy: What determines a false-positive test? Either not measuring induration, or that it was due to prior bcg, which seldom lasts more than 5 yrs. If someone has a negative PPD it means either that they do not have a focus of inactive tuberculosis or that they are anergic (incapable of reacting due to deficiency in immune mechanisms). ...Read more
Tb test site bled right after injection. Can this give a false positive?Obviously, it was not intradermal. Don't answer if you don't know how to.
Check with your doc: The test was not appropriately administered. You want to ask your doc for a new one. Or get the igra blood test which is better anyway. The skin test is almost in the museum of history of medicine. ...Read more
How accurate is this test :quantiferon-tb gold? And can they show up like false positive?I have test done and don't like the results i see .Scared
QFT Gold : Quantiferon gold can give false negetive or positive. Blood samples must be processed within 12 hours after collection while white blood cells are still viable. Test is not reliable among persons recently exposed to m. Tuberculosis, and in immunocompromised persons. False positive results can occur with m. Szulgai, m. Kansasii, and m.Marinum. ...Read moreSee 1 more doctor answer
9 wks preg. Tested positive for TB (blood test) doctor has not called. Could it be a false positive? Help I am so terrified. I have no symptoms.
Why was it done?: You may simply have been exposed and recovered, or this may be a false-positive. I'd relax. ...Read more
2 TB skin tests. Bumps measured 15cm. RN stated I possibly have LTBI & ordered QuantiFERON Gold in-tube test. Could anything cause a false positive?
Not at 15cm, but...: The bump is more likely 15mm, because 15cm is 6 inches and HUGE. A 15mm bump on a screening test is big but may still be a false positive (a screening test means the patient has NO symptoms of tuberculosis). If a patient has contacted somebody with TB, or has current symptoms, she likely has a true positive unless her bump is due to past BCG vaccine. The Quantiferon-TB blood test is very accurate ...Read moreSee 1 more doctor answer
Could a TB skin test be false positive if the needle was to deep? My arm bled after the test and now that its healing I have a large purple bruise
Wouldn't accept it: The test is standardized to represent the reaction to material places between layers of your dermis (skin) and would become invalid if it went too deep and bled. It deserves repeating.I would worry that it could be falsely negative if the test material dissipated into deep tissue.That could lead to a delay in proper treatment. A false positive would be unlikely& need eval ...Read moreSee 3 more doctor answers
Yes, I think so.: It may not be an absolute certainty, but i would advise the physician of the fact that there was a primary complex diagnosed and treated (assuming it was) either before the TB test or at the time of results if they are positive. I have never had positive results, but i was told that i had a primary complex - i always tell them the history just to be informationally complete. Best! ...Read more
Chest X ray: It is possible to have active TB with very little symptoms especially early on. However, it is more than likely that you carry the germ for TB in a dormant form, this is called latent tb. No symptoms are expected with latent tb. ...Read more
If there is a bump: When TB infects the body the infection gets walled off by antibodies. The medical person injects a manufactured antibody under your skin that reacts to the TB antibody. If a bump appears at the injection site after 48 hours it means you have the antibody to TB already in your body and therefore have TB infection. It does not mean that you have active disease or are contagious. ...Read more
TB Tests: I bet you could google image that question. A positive reaction is read after 48 hours from the test. It would be a raised redness greater than 5 mm in circumference. ...Read more
48-72 hours: Tb test is meant to be interpreted in 48-72 hours after being administered on the forearm. Make sure that the induration (not redness) is measured in that time frame & results documented by a health care provider. Further testing may be determined based on your results from the TB test. ...Read more
Size of induration: After the TB test, the skin at the site can develop swelling (induration). The size of this swelling (measured in millimeters by a health care provider within 48-72 hours) determines whether you have a positive result or not. It is important to not measure the area of redness but the actual size of the swelling around the test site. The cut off value for positive test is based on yr risk factors. ...Read more
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