A new skin test for tuberculosis (TB) may soon offer a simpler, more affordable way to detect the infection. In a first-of-its-kind human study, the test proved safe and showed strong accuracy in identifying active TB cases.
The Big Discovery: A new skin test combining two key TB proteins accurately identified most active TB cases in early trials. Who it helps: People at risk for TB, especially in low-resource settings where expensive blood tests are hard to access. The Catch: This is still a Phase 1 trial. More research is needed before it can replace current tests.
This new test could make TB screening more accessible and affordable worldwide.
Tuberculosis remains one of the world’s deadliest infectious diseases, killing over 1.3 million people each year. Finding it early is critical, but current tests have major drawbacks. Blood tests like IGRAs are accurate but expensive and require lab equipment. The old skin test (TST) is cheap but often gives false positives in people who had the BCG vaccine.
Researchers have been looking for a better option. Now, a new skin test may bridge that gap.
The Problem with Current Tests
TB is caused by Mycobacterium tuberculosis, a bacteria that usually attacks the lungs. About a quarter of the world’s population is infected, though most never get sick. Still, early detection saves lives.
Doctors rely on two main tests. The Tuberculin Skin Test (TST) is the traditional method. A nurse injects a small amount of tuberculin under the skin. If the area swells after 48–72 hours, it suggests TB infection. But the TST has a big flaw: it cross-reacts with the BCG vaccine, which many people receive as children. This leads to false positives.
The newer blood tests (IGRAs) avoid this problem. They measure immune proteins called interferons. But they require blood draws, lab processing, and cold storage—barriers in many countries.
A New Approach
Scientists tried to improve the skin test by using specific TB proteins that don’t react with the BCG vaccine. Early versions used two proteins: ESAT-6 and CFP-10. But they wanted even better accuracy.
This study tested a new combination: ESAT-6 paired with MPT64, a protein from a part of the TB bacteria called RD2. The idea is to give the immune system more targets to recognize.
Think of it like a lock and key. The TB bacteria have many unique “locks.” Current tests only check for one or two. By adding MPT64, this new test checks for three. More locks mean a better chance of catching the infection.
How the Study Worked
Researchers in China ran a Phase 1 clinical trial. They enrolled 60 people: 30 with active TB and 30 healthy volunteers. Each group was split into three dose levels (low, medium, high).
Everyone got a small injection under the skin, like a TB skin test. Doctors checked the injection site after 48 and 72 hours. The main goal was safety. The second goal was accuracy.
The test was very safe. Most side effects were mild—like slight redness or itching—and went away on their own. No serious problems occurred.
In people with active TB, the test correctly identified 87% of cases at 48 hours and 82.6% at 72 hours. That’s comparable to blood tests.
In healthy volunteers, only 13.3% had a false positive reaction. This means the test is specific and unlikely to be fooled by the BCG vaccine.
The test also matched well with IGRA results, confirming it targets the right immune response.
Here’s the catch: This was a small, early-stage trial. Larger studies are needed to confirm these results.
Where This Fits In
If approved, this test could be a game-changer for TB screening in low-income countries. It’s cheap, easy to use, and doesn’t require a lab. Health workers could administer it in clinics or even in the field.
This test is not available yet. It’s still in the research phase. If you’re concerned about TB, talk to your doctor about current testing options.
This was a small study with only 60 participants. It also focused only on active TB, not latent infection. More research is needed in diverse populations.
Researchers plan to run larger Phase 2 and Phase 3 trials. If those succeed, the test could be submitted for regulatory approval. That process usually takes several years.
