What is considered a positive TB test, 10mm or 15mm?

KelRN215, BSN, RN · Jun 17, 2018

15 mm is positive for everyone. 10 mm and even 5 mm are positive for some people. It depends on risk factors.

What Does a Positive TB Skin Test Look Like?

mzsuccess · Jun 17, 2018

15 mm is positive for everyone. 10 mm and even 5 mm are positive for some people. It depends on risk factors.
What Does a Positive TB Skin Test Look Like?

Thanks so much! very informative information!

My patient is 19 mm about the size of a dime but have no s&s I told the other nurse it was positive but she said no so I'm confused!

mzsuccess · Jun 17, 2018

He also have no other risk factors.

KelRN215, BSN, RN · Jun 17, 2018

Thanks so much! very informative information!
My patient is 19 mm about the size of a dime but have no s&s I told the other nurse it was positive but she said no so I'm confused!

That's a positive PPD but not necessarily indicative of TB. Remember that a positive PPD only means the patient has been exposed to TB, it doesn't tell you anything about the presence or absence of infection. The patient needs further testing.

mzsuccess · Jun 17, 2018

That's a positive PPD but not necessarily indicative of TB. Remember that a positive PPD only means the patient has been exposed to TB, it doesn't tell you anything about the presence or absence of infection. The patient needs further testing.

Thx thats what I thought.

DowntheRiver · Jun 17, 2018

. Remember that a positive PPD only means the patient has been exposed to TB, it doesn't tell you anything about the presence or absence of infection.

Not necessarily true. Recent live vaccination (MMR, VZV, Smallpox) in the last 28 days can cause a false positive. If you also currently have or have very recently had measles or smallpox it can also cause a false positive. It also depends on the age of the person as well, as a child under 6 months might pop a false positive.

Many other countries also vaccinate with the BCG so those individuals *most likely* are going to show positive forever. Best to just get a chest x-ray and/or TB Gold.

cleback · Jun 17, 2018

Not necessarily true. Recent live vaccination (MMR, VZV, Smallpox) in the last 28 days can cause a false positive. If you also currently have or have very recently had measles or smallpox it can also cause a false positive. It also depends on the age of the person as well, as a child under 6 months might pop a false positive.
Many other countries also vaccinate with the BCG so those individuals *most likely* are going to show positive forever. Best to just get a chest x-ray and/or TB Gold.

Do both xray and Quant gold. Skin tests are common false positives... in addition to the above, exposure to other mycobacterium can cause a positive. If the quant is positive, an xray will help rule out active tb disease.

Horseshoe, BSN, RN · Jun 17, 2018

Not necessarily true. Recent live vaccination (MMR, VZV, Smallpox) in the last 28 days can cause a false positive. If you also currently have or have very recently had measles or smallpox it can also cause a false positive. It also depends on the age of the person as well, as a child under 6 months might pop a false positive.
Many other countries also vaccinate with the BCG so those individuals *most likely* are going to show positive forever. Best to just get a chest x-ray and/or TB Gold.

I'm going to go out on a limb and guess that the patient has not recently had smallpox...

But good points made about false positives as well as the BCG.

mzsuccess · Jun 17, 2018

I'm going to go out on a limb and guess that the patient has not recently had smallpox...
But good points made about false positives as well as the BCG.

He has not had chickenpox, he's of Indian descent

Horseshoe, BSN, RN · Jun 17, 2018

He has not had chickenpox, he's of Indian descent

1)I did not say anything about chicken pox

2)what does being of Indian descent have to do with him not having had chicken pox?

Wiggly Litchi · Jun 17, 2018

15 mm is positive for everyone. 10 mm and even 5 mm are positive for some people. It depends on risk factors.
What Does a Positive TB Skin Test Look Like?

As a brit living stateside, 5mm was deemed positive for me

Gotta love that BCG vaccine...and the annual Tspot test haha