TB Test

Everything You Should Know About QuantiFERON-TB Test

QuantiFERON-TB test is the widely recommended revolutionary assessment for tuberculosis. This cutting-edge technology is a great option for people who need to be tested quickly and accurately.  

In this blog post, we will discuss what exactly QuantiFERON-TB is and its advantages. Before digging deep into this topic, let us first understand the significance of tuberculosis infection and when you should opt for diagnosis.

Significance of Tuberculosis

An infection known as tuberculosis (TB) is caused by the bacterium Mycobacterium tuberculosis. This infection is transmitted via droplet inhalation, or when someone inhales a small droplet of a sneeze or cough from an infected patient. Hence if a person has a confirmed case of TB, it is critical to take precautions to isolate them.

The bacteria can manifest in several ways, most commonly in the lungs, followed by kidneys, focal sensory systems, and different organs since they can go through the circulatory system.

The condition can be fatal for some patients, while for others there are no symptoms. A persistent cough that lasts for weeks, chest pain, and phlegm are the most common symptoms. Fatigue, unexplained weight loss, a lack of appetite, chillness, and fever are additional symptoms. The most vulnerable individuals to TB are those with weakened immune systems, such as those with HIV or diabetes.

Regardless of whether the patient shows side effects, the microbes can lay lethargic in the body. This is known as a different however comparable condition called latent TB infection (LTBI). These people will as a rule show a positive TB test, however, will have an ordinary chest x-ray. Patients with LTBI are not contagious, but if the patient’s immune system is compromised, the condition may relapse into an active TB infection. 

How is TB diagnosed?

A skin test and QuantiFERON-TB test can be used to diagnose TB. 

Tuberculin skin test

The Mantoux tuberculin skin test (TST) requires two visits to a healthcare provider. A small amount of tuberculin is injected underneath the skin of your forearm during the first visit to create a small raised area. Your physician will examine your skin for any palpable, raised, hardened, or swelling at the injection site 48 to 72 hours later. The entire test should be repeated if it is not read within 72 hours. Children under the age of 5 opt for this test.

Though widely used, TST has its limitations:

  1. Poor reliability 
  2. Possibility of false positives/specificity due to prior BCG vaccination and NTM (Nontuberculous mycobacteria) infection
  3. The test should be repeated if not read within 72 hours leading to additional cost. Hence, it’s not time-saving. 
  1. Lack of sensitivity since reaction disappears over time
  2. Not recommended as a gold standard

QuantiFERON-TB test

The Food and Drug Administration (FDA) approved the QuantiFERON-TB test (QFT) in 2001 as a method for detecting latent Mycobacterium tuberculosis infection, as stated by the U.S. Centers for Disease Control. 

White blood cells will release interferon-gamma (IFN-γ) when they come into contact with TB antigens if the patient has M. tuberculosis. The amount of interferon-gamma released in response to the antigens when incubated overnight with purified protein derivative (PPD) from M. tuberculosis and control antigens is the basis for the QuantiFERON-TB gamma results.

The limitations in the tuberculin test have been addressed in QuantiFERON-TB (QFT):

  • No need for a second visit for QuantiFERON-TB assessment. Just a single patient visit is enough
  • Unlike the tuberculin skin test, repeated testing has no booster effect
  • There are no adverse hypersensitivity reactions associated with the in vitro assay
  • Unlike the tuberculin skin test, this test is more specific and will not produce false positives if prior BCG vaccination is administered
  • This method is more specific and sensitive for determining whether a patient has active or latent tuberculosis infection
  • Evaluates responses to multiple antigens simultaneously
  • QFT results are less susceptible to reader bias and error than TST results

There is only one limitation with this test. Blood tests should be incubated with test antigens within 12 hours after sample collection while white cells are still viable. At DLW, the sample is directly collected at the source in the special tubes coated with test antigens to ensure prompt incubation.

What is the meaning of a positive QuantiFERON test (QFT)?

TB infection is indicated by a positive QuantiFERON (QFT) reaction. Simply put, this indicates that the individual has come into contact with tuberculosis (TB) bacteria.

If the QuantiFERON test (QFT) comes positive, what next?

Any adult or child who responds positively to the QuantiFERON test (QFT) should be tested for tuberculosis symptoms. A chest x-ray may also be necessary. Latent tuberculosis (TB) is found in individuals who do not exhibit symptoms of tuberculosis (TB), have a normal chest x-ray, and have a positive QuantiFERON test (QFT).

Need QuantiFERON-TB testing?

If you’re thinking about getting QuantiFERON-TB tested, it’s important to know where to find a reputable lab near you that does.

The highly accurate and recommended QuantiFERON-TB test can be performed without a doctor’s visit. However, the request for this test should come through your physician only. It is a cost-effective, safe, and simple method of detecting tuberculosis. QuantiFERON-TB might be the best option for you if you’re looking for a reliable TB test.

Are you looking for an affordable way to get tested for QuantiFERON-TB? Look no further than DLW! Our group of specialists will ensure that your test results are precise, reliable, and affordable. Take advantage of our DLW diagnostics right away without waiting any longer!