The TB (tuberculosis) blood test is used to determine if you have this disease. It spreads through the air from person to person. The skin test is often used to determine the presence of TB, but the interpretation of the results can be subjective. Having multiple skin tests can also create a false positive. That’s why the TB blood tests are often used for a better confirmation.
The TB blood test will measure how the immune system reacts to the presence of TB bacteria. Depending on the strength of the immune response, a medical provider can determine if there is the possibility of an infection. There are two currently approved TB blood tests that are on the market right now in the United States: the QuantiFERON TB Gold test and the T-SPOT TB test.
These tests can be repeated as necessary for screening purposes. That is why they are becoming the preferred method of TB detection.
Who Needs the TB Blood Test?
If there isn’t a suspected risk of a TB infection, then this blood test is not necessarily. It will generally be ordered for people who have spent time with someone who has a confirmed infection or will be working in a high-risk environment where TB may spread. Those who have a compromised immune system may also have regular TB blood testing even without the signs or symptoms of the disease.
Prisons, jails, residential treatment centers, and nursing homes are high-risk areas in the United States for TB to spread. Those who work with individuals who take illicit drugs should also speak to their medical provider about being tested. Some employers may require a TB blood test to be taken before an offer of employment will be officially extended.
Anyone who is experiencing the symptoms of TB should also consider speaking with a medical provider about being tested. This includes a fever that refuses to break, sweating at night, a cough that won’t go away, and unexpected weight loss.
BCG vaccination does not affect the integrity of a TB blood test like it can the skin test.
What Do My Test Results Mean?
A positive TB blood test result doesn’t necessarily mean that a person has an active infection. It will only indicate that there was an infection at one time. Further testing will be required if the test is positive to determine if there is a latent infection or TB disease. A chest x-ray and other samples will be requested to screen out these conditions.
A negative TB test means that the blood sample taken did not react to the presence of TB bacteria. This typically means that there is no latent infection or TB disease present.
Why Is TB Detection So Important?
Tuberculosis is one of the world’s most deadliest diseases. From a global perspective, 1 in 3 people is infected with the bacteria that causes TB. In 2013, there were 9 million people confirmed to be suffering from TB and about 1.5 million people died from their infection. It is the leading cause of death in individuals who also have HIV.
Infection rates are much lower in the United States. From 2013 data, there were just over 9,500 cases that were diagnosed. That translates to an infection rate of about 3 people per 100,000 in the general population. Those rates are about 4% lower than what 2012 figures that were released by the Centers for Disease Control and Prevention.
Out of the 1.5 million people confirmed to have been killed because of tuberculosis complications, just 536 of them came from the United States. That number has decreased by almost 70% since 1992, which is the last year that infection rates peaked.
65% of the confirmed cases of TB in the United States occurred in individuals who were born in a different country. When foreign-born US citizens are compared to US born citizens, the TB infection rate is 13x higher. The danger with this is that certain strains of TB have become resistant to multiple drugs. Although the US rate of infection of resistant TB is below 2%, it has been on the rise since 1993 when these strains were discovered.
The TB blood test can help to determine if there is a need to treat a latent infection or disease. It may be used most often as a screening tool for employment or for caregivers, but it can also provide information that could save a life. If you suspect that you’ve been exposed to TB or plan to work in a high-risk environment, then discuss with your doctor the pros and cons of opting for a blood test instead of the standard skin test.