How accurate are simple tests for diagnosing tuberculosis in the lungs?

Key messages

• We only found one relevant test, the MiniDock. In adults and adolescents with symptoms of tuberculosis in their lungs (pulmonary TB), MiniDock correctly identified those who did have TB and ruled out TB in those who did not have TB. MiniDock identified TB less accurately in people living with HIV and in those without visible bacteria in the mucus brought up by coughing (sputum), called smear-negative TB.

• MiniDock was less accurate than Xpert Ultra in correctly identifying TB, but the two tests had similar accuracy in ruling out TB. MiniDock was more accurate than using a microscope to identify TB.

• We need more information about whether the test works in children, and whether it works in community clinics (not laboratories).

Why is improving the diagnosis of tuberculosis important?

Tuberculosis (TB) is an infection that usually affects the lungs (pulmonary TB). Although it sometimes affects other parts of the body, we are only looking at pulmonary TB. TB spreads from person-to-person through the air and causes more deaths worldwide than any other infectious disease. Rapid diagnosis can help people start treatment earlier, reduce illness and death, and stop the disease spreading to others.

What is the NPOC-NAAT test?

Most TB tests are done in a laboratory, with bacteria grown from the person's sputum (culture) being the best available test for confirming TB. However, this is limited by complicated laboratory requirements and needing to wait several weeks for a result. A new type of test, the 'near point-of-care nucleic acid amplification test' (NPOC-NAAT) is designed to be used closer to where people seek care than standard laboratory-based tests. They can be used in community screening events or local health clinics, by people without very technical training. In this review, only one test met the NPOC-NAAT definition, which is based on ease of use outside of laboratories: the Pluslife MiniDock MTB NAT Card (MiniDock). This test uses a small piece of cotton wool (swab) which can be dipped in a small amount of the mucus brought up when someone coughs (sputum) or used to swab the surface of the tongue; this review is focused on its use with sputum.

What did we want to find out?

We wanted to find out how well NPOC-NAATs can detect TB using sputum or fluid collected from the lungs, in adults and adolescents. In children who might have TB, we looked at similar samples, including sputum, fluid collected from the lungs, and samples taken from the nose or stomach. We also wanted to compare NPOC-NAATs with other tests (Xpert Ultra, microscopic evaluation) when studies assessed them side by side. In particular, we measured how well the tests correctly identified people with or without TB.

What did we do?

We searched for studies that assessed NPOC-NAATs against culture. We included published studies and unpublished studies, identified through a World Health Organization (WHO) public call for data. We combined the results of the studies to assess how well the tests worked, and rated our confidence in the evidence, based on factors such as study methods and sizes.

What did we find?

We found five studies that used MiniDock to diagnose TB using sputum samples. The studies included 3291 people and 553 (17%) of them had TB.

MiniDock correctly identified about 85 out of 100 people who had TB (so missed diagnosing 15 people). In 100 people without TB, MiniDock correctly ruled out TB in about 98 of them. MiniDock was less accurate in identifying TB in people living with HIV (79 out of 100 people correctly diagnosed). Among people with TB not detected by microscopic evaluation (smear-negative TB), MiniDock was less accurate, identifying 67 out of 100 people with tuberculosis, compared to people with TB detected by microscopic evaluation (smear-positive TB, 99 out of 100 people correctly diagnosed).

In studies that compared tests directly, MiniDock was less accurate than Xpert Ultra in correctly identifying people with TB, but the tests correctly ruled out TB in similar numbers of people who did not have the disease. MiniDock was more accurate than microscopic evaluation of sputum in correctly identifying people with TB.

Only one study included children, and none of them had TB, so we could not estimate how well the test detects TB in children.

What are the limitations of the evidence?

The evidence has several important limitations.

• We only found one relevant NPOC-NAAT test (MiniDock).

• The studies only used sputum (not fluid from the lungs, or other types of sample).

• Most studies did the MiniDock test in a laboratory, not in places close to where people need to be tested, so results may not fully apply to routine use in local health clinics or community settings.

• We do not know if the test is accurate in children because none of the children included in the study had TB.

• We also found limited data for people without symptoms who screen positive for tuberculosis and people with advanced HIV disease.

How up to date is this evidence?

This review is current to July 2025.