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Doctor insights on: What Does A Tb Test Look Like When It Is Negative

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What does a negative TB test look like?

What does a negative TB test look like?

Doc: Either your blood test igra is negative or your skin testing does not show any "bump". This should always be checked by a professional since even health care workers report false results. Best to check with a doc and not pa or np or nurse. ...Read more

Dr. Scott Lindquist
615 doctors shared insights

Mycobacterium Tuberculosis Infection (Definition)

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


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What do a positive and negative TB test look like?

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

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What does a + TB test look like?

What does a + TB test look like?

Positive PPD test: A positive TB test should look like hard, raised bump with size >5to15 mm depending on of the risk category you are in. It should be read in between 48 to72 hours. It is the hardness and not redness which is read. Thanks. ...Read more

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What does a positive TB test look like?

What does a positive TB test look like?

Skin test: If you had a PPD skin test and you have no risk factors, a positive test is when after 48 to 72 hoursyou have swelling in the site and redness that measures more than 15 mm, it is considered a positive tb. Test. ...Read more

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What does a positive TB test look like? How is this treated?

What does a positive TB test look like? How is this treated?

What is important: Is what it feels like — not how it looks. Induration is palpated & measured. Treatment (such as INH) is determined once it is established where this is latent or active TB and the type. ...Read more

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What should my skin look like after taking a TB test?

What should my skin look like after taking a TB test?

See below: A positive PPD is determined by the presence of swelling(induration) around the injection site. Little or no swelling indicates a negative test. Reddness is not used to determine a neg or pos test. ...Read more

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If I tested negative from a TB test and had been around someone who tested positive am i at risk of contracting tb?

TB risk: Yes, the PPD test is not 100%. You might want to get it repeated a month later to see if it is booster positive. Of course, it is also possible that you didn't catch it. Many doctors are around people with TB a lot and never catch it. ...Read more

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When you take TB test and no bubble pops up is it negative?

A positive: Tb test is associated with elevation you can feel at the injection site -- not likely to be a discrete bubble. Redness doesn't count -- you have to feel something. ...Read more

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When you get a TB test and no bubble pops up does that mean its negative?

Yes: If there is no raised area which measures at least 5 mm in diameter the test should be considered negative. ...Read more

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How long would it take for TB test marks to go away? Mine came back neg but the mark went from unremarkable to large and red after 4 days now. Thx.

TB Test: There can be several reasons why a TB test takes longer to reactt. If you do have a large reaction as you describe you should go back to your doctors office to show it to them as theymay decide it is a delayed positive test ...Read more

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TB test: neg >72 hrs but now large lump as time goes on? How long for mark to go away?

TB test: neg >72 hrs but now large lump as time goes on? How long for mark to go away?

Negative, give time: As long as there was no hardened lump at the infection site within that first 72 hours that was greater than 15mm (or less if you have risk factors), you are still considered negative. It can take some people up to a week or so for the redness and swelling to recede. Try ice several times a day to help with any swelling. ...Read more

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Hi, i recently had a TB test. It looks round and red but no bump. It was read as negative by nurse buy after 5 days, the redness is still there.

Hi, i recently had a TB test. It looks round and red but no bump. It was read as negative by nurse buy after 5 days, the redness is still there.

No bump = negative: A PPD TB skin test is where one needle injects a tiny amount of material under the skin. It is used to check for exposure to tb. The "bump" is measured, and any redness is not measured unless it is raised above the normal skin surface. A "bump" is positive if 5, 10, or 15mm, depending on the patient's circumstances. If positive or if worried, a blood test is done. Redness resolves in a week or so. ...Read more

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I got a tb test its itching and red. Size of a quarter maybe but it doesn't seem to be swollen.pos? Neg?

I got a tb test its itching and red. Size of a quarter maybe but it doesn't seem to be swollen.pos? Neg?

Allergy to ppd: Some people get a 'reaction' like that to a ppd-but it's not indicative of a positive TB test-instead it's an allergy to the material used for the test. A doctor or trained professional can look at it and determine if it's positive based on 'firmness' (we call it induration) under the skin where the ppd was placed. Itchy and red skin is something else. If it's bad, some hydrocortisones cream helps ...Read more

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Took a TB test last monday & the nurse said it was negative on wednesday but now I have a red spot should I worry?

Took a TB test last monday & the nurse said it was negative on wednesday but now I have a red spot should I worry?

Not reversible: It is common for people to have some allergy to the components of the test medicine. The reaction for positive test is specifically the bump felt and not the redness. It will go away. ...Read more

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I am a medical assistant and had my TB test come back positive but cxr negative. Is there any follow up I should do?

I am a medical assistant and had my TB test come back positive but cxr negative. Is there any follow up I should do?

Yes: For a person with a positive PPD skin test and a negative chest x-ray, if he had a BCG vaccine in the past, he can do a quantiferon TB blood test to see if he was exposed to real TB or just to the BCG shot. If he never had a bcg, he can talk with his doctor to decide if he should take inh prophylaxis against tb. If it is not sure if he truly was positive on the skin test, he can repeat it. ...Read more

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If I take Benadryl (diphenhydramine) a day after I got the TB test will it interfere with it? (make it positive/negative)

No effect: The reactivity of the tuberculin test relies on immune factors not allergic responses. Benedryl will have no effect on that process. ...Read more

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I have this cough for 10 months now, medical tests including TB test are all negative. Antibiotics didn't help either. Please what could be wrong?

I have this cough for 10 months now, medical tests including TB test are all negative. Antibiotics didn't help either. Please what could be wrong?

Persistent cough?: You have had a persistent cough for ten months. If you are living with other human beings who do not have a similar cough you can be pretty confident that you don't have a very contagious condition. Think about cough secondary to post nasal drip, asthma, reflux. You should go see a pulmonary disease doctor. He will help you find out what's going on. Good luck. ...Read more

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Blood draw from rt a/c and tb test below it. 5 days later red dots around antecubital area and pimple next to red but neg tb test. Normal? Coincidence

Blood draw from rt a/c and tb test below it. 5 days later red dots around antecubital area and pimple next to red but neg tb test. Normal? Coincidence

2 seperate: Most probable cause is you had some minor localized reaction to the blood draw (possible contact dermatitis if you had a bandaide on the area or tape, etc.) and the TB test below the site of the same arm, would not have anything to do with the injection site of the blood draw. Best wishes. ...Read more

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Tb skin test negative, quentform TB test negative, bone marrow biopsy results indicative of TB (reacts to ziehl niehlssen), PCR negative. How come?

No...actually: The zn stain is a broad stain for acid fast bacilli of which mycobacterium tuberculosis is one of many. The specific tests like quantiferon or the pcr test are against you having tb. The culture is the "gold standard" but you will need to wait for it. It might turn out be a cousin of TB and that too will grow out of culture. Stay on TB meds until they are certain of the AFB positive organism. ...Read more

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How badly does a TB test hurt? I'm extremely terrified of needles and would like to know how bad it will hurt.

None: It does not hurt much. You would feel it as much as you feel an insect bite. To distract yourself get an activity going while it is being done. Goodluck ...Read more

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Does a TB test hurt?

Does a TB test hurt?

Not really: It is a tiny needle, just within the layers of the skin to create a fluid bubble. Takes a few seconds to apply. ...Read more

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What does a TB test involve? Never had one and need it for cna class I start in November. How often do I need it done?

A small: Injection into you forearm and then examination few days' later to check for size of induration, you must have them annually ...Read more

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What is a 2-part TB test?

Outdated?: May be tuberculosis skin testing?

Igra or quantiferon gold blood testing is at least as good or even better. Discuss with your doc.

The blood test is usually better than the skin test. ...Read more

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How long are TB test good for?

Until today: You tested negative today? Great. But maybe you will inhale the bug tonight? Then your TB test will change.

Once positive always positive. ...Read more

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Can I have a TB test with a cold?

Yes: The memory cells for TB are in the body and the test will still be valid if positive. The only problem are in people who have lower immune system but not quite bad enough to cause reactivation as they can develop anergy or false negative test. ...Read more

Dr. Klaus d Lessnau
1,215 doctors shared insights

Tuberculosis (Definition)

A potentially serious infectious bacterial disease that ...Read more