Review of PPDs

We have a lot to learn regarding TB, but regarding the targeted testing for latent tuberculosis infection, here is a VERY QUICK review of what constitues a positive PPD:

>0 mm is considered a positive reaction if the patient:

• Is HIV-positive or immunocompromised AND are recent contacts to known or suspected infectious TB disease, regardless of previous treatment of LTBI
• Is HIV-positive with fibrotic changes on CXR consistent with prior TB who have received inadequate or no treatment for TB disease
• Is a child <5>

>5 mm is considered a positive reaction if the patient:

• Is HIV-positive
• Is a contact to known or suspected infectious TB case identified within the last two years
• Has fibrotic changes on CXR consistent with prior TB and have received inadequate or no treatment for TB disease
• Is Immunocompromised (receiving >15mg per day of Prednisone for one month, other immunosuppressive drugs, organ transplant recipients, persons taking TNF inhibitors)

>10 mm is considered a positive reaction if the patient:

• Is foreign-born from Asia, Africa, Carribean, Latin America, Mexico, South America, Pacific Islands, or Eastern Europe)
• Has converted their TST within two years
• Has a medical condition placing them at high-risk for TB Disease (DM, CRI, Chronic malabsorption syndrome, Leukemias and Lymphomas, Cancer of the head and neck, Silicosis, Weight loss of >10% ideal body weight, gastrectomy or intestinal bypass)
• Is an injection drug or crack cocaine user
• Is a child <4>
• Works in a mycobacterial lab

*Also, this cutoff is used per the clinicians judgement for: residents of long-term care facilities and homeless shelters, are inmates in the DOC, OR are employees in prisons/jails, long-term care facilities, hospitals/health care facilities, adult day-care centers for HIV patients, homeless shelters).

>15 mm is considered a positive reaction if the patient:

• Has NO risk factors for TB

Hope this helps!

Yvonne Carter, MD