The QuantiFERON-TB Gold Plus (QFT-Plus) test is a blood test designed to detect infection with Mycobacterium tuberculosis, the bacteria responsible for tuberculosis (TB). It serves as an aid in diagnosing TB infection by measuring the immune system’s response to specific TB proteins, providing objective results from a single blood draw.
What a Positive Result Indicates
A positive QuantiFERON-TB Gold Plus test result signifies infection with Mycobacterium tuberculosis bacteria. The test detects this by measuring the release of interferon-gamma from immune cells stimulated by specific TB proteins.
A positive QFT-Plus result does not differentiate between latent TB infection (LTBI) and active TB disease.
Latent TB occurs when bacteria are present but inactive, causing no symptoms and not being contagious. Individuals with LTBI cannot spread the bacteria, though they carry a risk of developing active TB disease in the future.
In contrast, active TB disease means the bacteria are multiplying and causing symptoms. People with active TB disease can potentially spread the bacteria to others through the air.
A positive QFT-Plus test indicates TB bacteria are present, prompting further investigation to determine the specific state of the infection.
Immediate Follow-Up After a Positive Result
A positive QFT-Plus result necessitates immediate medical evaluation to determine if the infection is latent or active. This evaluation includes a medical history, physical examination, and a chest X-ray to look for signs of active TB in the lungs.
If active TB is suspected, additional tests like sputum tests may be conducted to isolate the bacteria and confirm diagnosis.
The QFT-Plus test screens for M. tuberculosis infection but does not definitively diagnose active disease. A comprehensive medical assessment is essential to guide next steps.
Treatment and Prevention Considerations
Once medical evaluation determines if it is latent or active TB, specific treatment pathways begin.
For latent TB, treatment prevents progression to active disease, often involving a shorter course of medication, typically for three to four months, to kill inactive bacteria.
Active TB requires a longer, more complex regimen with multiple anti-TB drugs for several months. This multi-drug approach cures the disease and prevents drug resistance.
Adherence to the full course of medication is crucial for both latent and active forms of TB to ensure successful outcomes and prevent recurrence.
For active TB, public health measures like contact tracing may be initiated to identify and test exposed individuals, helping control spread.
Treating both latent and active infections contributes to reducing the burden of tuberculosis.