QuantiFERON test (QFT) is a blood test which helps in the diagnosis of tuberculosis (TB). QuantiFERON test (QFT) is an interferon gamma release assay (IGRA). It is considered to be an alternative test to tuberculin skin test or Mantoux test for diagnosis of tuberculosis (TB).
How does a QuantiFERON test (QFT) work?
In the QuantiFERON test (QFT) a blood sample of the child is required. The white cells or the lymphocytes in the blood are exposed to specific TB antigens (ESAT-6/CFP-10) and the immune response is measured. The results typically are available in 72 hours. The QuantiFERON test (QFT) has a TB antigen tube and a control tube.
What does a positive QuantiFERON test (QFT) mean?
A positive reaction in the QuantiFERON test (QFT) indicates infection with the Mycobacterium tuberculosis (TB), the bacteria which causes tuberculosis (TB). In simple terms mean that the person has been exposed to tuberculosis (TB) bacteria.
What is the next step after a positive QuantiFERON test (QFT)?
Any child or adult with a positive reaction in the QuantiFERON test (QFT) needs to be screened for symptoms of tuberculosis (TB). In addition a chest xray and ultrasound of the tummy might be required. Patients with no tuberculosis (TB) like symptoms and a normal chest xray/ultrasound with a positive QuantiFERON test (QFT) have latent tuberculosis (TB). Common symptoms of active tuberculosis (TB) are fever, night sweats, weight loss, cough, sputum and enlarged lymph nodes. The QuantiFERON test (QFT) does not distinguish between latent vs active tuberculosis (TB).
How do we treat patients who have a positive QuantiFERON test (QFT)?
Patients who have a positive QuantiFERON test (QFT) but have no tuberculosis (TB) like symptoms and normal chest radiograph have latent tuberculosis (TB). Since tuberculosis (TB) is endemic in India and reinfection rates are very high, everyone with latent tuberculosis (TB) is not treated as done in western countries.
These are certain situations when latent tuberculosis (TB) requires treatment. Family contacts of a patient with pulmonary tuberculosis (TB) who have a QuantiFERON test (QFT) requires treatment for latent tuberculosis (TB). The current national guidelines suggest treating all contacts irrespective of age. The previous guidance was to treat only children less than 6 years of age. In addition anyone who is at a risk for immunosuppression like children undergoing cancer treatment, diabetes, kidney disease or any other treatment where the immunity is likely to be suppressed also requires treatment for latent tuberculosis (TB) if they have a positive QuantiFERON test (QFT).
In case your child is having tuberculosis (TB) like symptoms or has been found to have a positive QuantiFERON test (QFT) you need to get in touch with a child tuberculosis (TB) specialist for proper diagnosis and treatment (if needed).
