From the Guidelines
IGRA is generally preferred over the Mantoux test for detecting tuberculosis infection in most clinical settings, due to its higher specificity and convenience. IGRAs, such as QuantiFERON-TB Gold and T-SPOT.TB, measure the immune response to TB proteins in a blood sample, whereas the Mantoux test involves injecting tuberculin purified protein derivative (PPD) under the skin and measuring the resulting induration after 48-72 hours 1. The advantages of IGRAs include requiring only one patient visit, results being available within 24 hours, and not being affected by prior BCG vaccination, making them more specific for TB infection 1.
Some key points to consider when choosing between IGRA and Mantoux test include:
- IGRAs are particularly recommended for BCG-vaccinated individuals, healthcare workers requiring serial testing, and those who may not return for TST reading 1
- The Mantoux test remains useful in resource-limited settings and for mass screening 1
- Both tests cannot distinguish between latent TB infection and active TB disease, so additional evaluation including chest X-ray and sputum testing is necessary when either test is positive 1
- The choice of test should be based on the individual's risk factors, medical history, and the availability of resources 1
In terms of guidelines, the WHO recommends using either IGRA or Mantoux test for testing latent tuberculosis infection (LTBI) in high and upper-middle income countries with a tuberculosis incidence less than 100 per 100 000 population per year 1. The CDC also provides guidance on the use of IGRAs in the diagnosis of M. tuberculosis infection in adults and children, recommending that TSTs and IGRAs may be used as aids in diagnosing M. tuberculosis infection 1.
Overall, the choice of IGRA over Mantoux test should be based on the individual's specific situation and the availability of resources, with the goal of improving morbidity, mortality, and quality of life outcomes.
From the Research
Comparison of IGRA TB and Mantoux Test
- The IGRA TB test and the Mantoux test are two diagnostic tools used to detect latent tuberculosis infection (LTBI) 2, 3.
- The IGRA TB test is preferred in populations that have been vaccinated with bacille Calmette-Guérin (BCG) due to its higher specificity 2.
- The Mantoux test, also known as the tuberculin skin test (TST), is still widely used, especially in situations where cost or logistical advantages exist 2.
- Both tests have limitations, including low positive predictive values, and there is a need for tests that can differentiate between the various stages of TB infection and better predict future TB risk 2, 3.
Advantages and Disadvantages of Each Test
- The IGRA TB test has superior specificity and is not affected by BCG vaccination or other environmental mycobacteria 3.
- However, the IGRA TB test is more expensive and has logistical and organizational constraints 3.
- The Mantoux test is less expensive and more widely available, but it can be associated with technical errors and has limited positive predictive value 3.
Current Recommendations and Practices
- The World Health Organization (WHO) recommends using either the TST or IGRA to detect LTBI in high-income and upper-middle-income countries with estimated TB incidences less than 100 per 100,000 population 3.
- A study in the United States found that approximately half of healthcare providers reported routinely testing non-U.S.-born patients for TB, with 35.7% exclusively ordering recommended blood tests (IGRA) and 44.2% exclusively ordering skin tests (TST) 4.
- Another study found that the QuantiFERON-tuberculosis Gold-Plus assay (QFT) was used to assess M tuberculosis sensitisation in adults participating in a clinical trial for a live-attenuated Mycobacterium tuberculosis vaccine (MTBVAC) 5.