TB Blood Test Benefits and Recommendations

Basics on the TB Blood Test and Why It May Be Preferred Over the TB Skin Test

QuantiFERON-TB Gold in Tube
Photograph Courtesy Cellestis, a QIAGEN company

There are two different types of tests a person can get when being tested for TB – the traditional skin test or a blood test. With that, testing for TB is extremely important in people with HIV, especially considering that TB is the most common cause of death in people with HIV worldwide, according to a 2005 article in JAMA

Let's take a close look at the TB blood test, and explore why it may be a good option for you.

What is the TB Blood Test?

On December 15, 2005, the U.S. Food and Drug Administration (FDA) approved an antigen-based tuberculosis (TB)  test called the QuantiFERON-TB Gold as an optional test to the traditional PPD skin test.

While the PPD skin test involves having a healthcare provider inject a fluid underneath the skin in the forearm of the person being tested, the newer TB test is a blood test, also known as intereron-gamma release assay (IGRA).

What are the Benefits of the TB Blood Test?

One of the most common problems associated with the PPD is patient follow-up. Once the PPD test is administered, the patient needs to return 48 to 72 hours later to have the skin test interpreted. Such delays often result in lost patients, particularly for those who live far away, or have a history of poor clinic attendance.

In addition, there is sometimes error in the interpretation of person's skin reaction to the tuberculin-ppd injection.


The QuantiFERON-TB Gold requires only a simple blood test. The patient, therefore, has no need to return to interpret skin test results, there is less chance of interpretation error, and far fewer changes of returning false positives when compared to the PPD. Better yet, results are returned in around 24 hours.

The only real limitations to the test are that bloods need to be tested within 12 hours —generally a negligible problem in much of the U.S. — and that drawing errors can sometimes affect the results

What is the New TB Blood Test?

In October 10, 2007, the FDA approved an updated version of the test called the QuantiFERON-TB Gold in Tube, which has a specificity of greater than 99% and a sensitivity of around 92% in those with active TB.  (Specificity is defined the percentage of true negative results, and sensitivity is the percentage of true positive results.)

With the new test, blood is taken in three collection tubes which are implanted with dried antigen. In addition, the bloods can now be tested within 16 hours of  being drawn.

Choosing a TB Test

On June 25, 2010, the Centers for Disease Control and Prevention (CDC) recommended that IGRAs be used as the preferred means for TB testing in many patients, including those who have been previously vaccinated with the bacille Calmette-Guérin, or BCG vaccine, or who may be unlikely to return for skin test results.

Of course, please talk with your doctor about which test is the best for you.


Centers for Disease Control and Prevention (CDC). "Guidelines for Using the QuantiFERON-TB Gold Test for Detecting Mycobacterium tuberculosis Infection, United States" Morbidity and Mortality Weekly (MMWR). December 16, 2005; 54(RR15);49-55.

Perry, S.; Sanchez, L.; Yang, S.; et al. "Reproducibility of QuantiFERON-TB Gold In-Tube Assay." Clinical and Vaccine Immunology. March 2008; 15(3):425-432.

CDC. "Updated Guidelines for Using Interferon Gamma Release Assays to Detect Mycobacterium tuberculosis Infection --- United States, 2010." Morbidity and Mortality Weekly (MMWR). June 25, 2010; 59(RR05):1-25.

Raviglione MC, Snider DE Jr. & Kochi  A. Global epidemiology of tuberculosis. Morbidity and mortality of a worldwide epidemic. JAMA. 1995 Jan 18;273(3):220-6

HIVInSite. (2013). Tuberculosis and HIV.

Edited by James Myhre and Dennis Sifris, M.D.

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