What is the Difference Between QuantiFERON Gold and T-SPOT?

QuantiFERON Gold and T-SPOT are both interferon-gamma release assays (IGRAs) used to diagnose latent tuberculosis infection (LTBI). However, they have some differences in their methodology and performance:

1. Detection method:

• QuantiFERON Gold: Measures interferon-gamma (IFN-γ) in the supernatant of antigen-stimulated cells by enzyme-linked immunoassay.
• T-SPOT: Detects individual memory T cells that produce IFN-γ in response to M. tuberculosis antigens, using the enzyme-linked immunospot technique.

1. Sensitivity:

• A study comparing the sensitivity of QuantiFERON Gold In-Tube (QFT-GIT) and T-SPOT.TB found that T-SPOT.TB had a higher overall sensitivity (91.0% vs. 80.2%). However, another study found that the sensitivity of QFT-PLUS, an updated version of QuantiFERON Gold, was higher than that of T-SPOT.TB, although the 95% CI was imprecise.

1. Specificity:

• QuantiFERON Gold has a specificity of 97%.

1. Patient age:

• Both QuantiFERON Gold and T-SPOT.TB showed a decrease in sensitivity with increasing age, but the decline was statistically significant for QuantiFERON Gold and not for T-SPOT.TB when adjusted for other factors.

1. Populations:

• QuantiFERON Gold has been found useful in younger patients (7-9 years old) and those with HIV co-morbidity.

In summary, both QuantiFERON Gold and T-SPOT are IGRAs used for diagnosing LTBI, but they have different detection methods, sensitivities, and specificities. T-SPOT.TB appears to have a higher overall sensitivity, while QuantiFERON Gold has a higher specificity. The decline in sensitivity with increasing age is more pronounced for QuantiFERON Gold than for T-SPOT.TB.

Comparative Table: QuantiFERON Gold vs T-SPOT

QuantiFERON Gold and T-SPOT.TB are both interferon-gamma release assays (IGRAs) used for the diagnosis of infection with Mycobacterium tuberculosis, but they have some differences in their specificity, sensitivity, and testing methods. Here is a comparison table of the two tests:

QuantiFERON Gold, also known as QuantiFERON-TB Gold Plus, measures the immune system response of T cell activation to a possible M. tuberculosis infection by using a single mixture of several antigens, causing the immune system to yield Interferon-γ (IFN-γ). It has a 97% specificity and a sensitivity of 94.1%. The test is effective and efficient, with a 24-hour turnaround time, although this can be elongated due to laboratory and provider delay.

T-SPOT.TB, on the other hand, is an enzyme-linked immunospot (ELISPOT) methodology that counts the number of T cells activated by M. tuberculosis antigens. It has a sensitivity of 95.6% and a specificity of 97.1%. The T-SPOT.TB test is the only blood test cleared by the FDA for patients as young as 2 years old.