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

  1. In school I was taught 15mm but on CDC its giving two different answers which can i go by for standard?
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    About mzsuccess

    Joined: Oct '12; Posts: 342; Likes: 139

    26 Comments

  3. by   KelRN215
    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?
  4. by   mzsuccess
    Quote from KelRN215
    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!
  5. by   mzsuccess
    He also have no other risk factors.
  6. by   KelRN215
    Quote from mzsuccess
    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.
  7. by   mzsuccess
    Quote from KelRN215
    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.
  8. by   DowntheRiver
    Quote from KelRN215
    . 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.
    Last edit by DowntheRiver on Jun 17 : Reason: ETA: most likely
  9. by   cleback
    Quote from DowntheRiver
    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.
  10. by   Horseshoe
    Quote from DowntheRiver
    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.
  11. by   mzsuccess
    Quote from Horseshoe
    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
  12. by   Horseshoe
    Quote from mzsuccess
    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?
  13. by   Wiggly Litchi
    Quote from KelRN215
    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
  14. by   mzsuccess
    Quote from Horseshoe
    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?
    1) I meant smallpox

    2) Some countries TB are more prevalent just thought I'd mention

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