A faster, more accurate tuberculosis test has been developed by scientists.
Existing TB tests do not always detect bacteria
The microscopic-observation drug-susceptibility (MODS) test is also cheaper and more sensitive to drug resistant strains than current tests.
It yields results in an average of seven days, and could help save many lives, particularly in developing countries - where TB is rife.
Details of the test, developed by UK, US and Peruvian researchers, feature in the New England Journal of Medicine.
The researchers hope it will lead to faster treatment for many people, reducing the severity of their symptoms, and the chances they will infect others.
It is thought that more than two million people die each year from TB.
The common strain is almost 100% treatable, but multi-drug resistant strains are becoming an increasing problem.
At present, the World Health Organization recommends the sputum smear microscopy test, which analyses the material expelled from the lungs by a deep cough.
However, the test, although fast, is not accurate in around 50% of cases, and it can take up to six weeks to culture the sample, confirm the results and determine whether it is resistant to drugs - these detailed checks are only rarely available in the developing world.
The MODS test allows doctors to diagnose TB twice as quickly as previous gold-standard culture tests and to identify multi-drug resistance in a third of the time.
In tests on nearly 4,000 sputum samples MODS identified TB with 97.8% accuracy - significantly out-performing the current tests.
MODS works by culturing the TB organism in a liquid, rather than the traditional solid substance.
This enables it to grow more rapidly, and for scientists to detect its characteristic pattern of tangles or coils under a microscope relatively easily.
The liquid media also means TB drugs can be more easily administered for testing: if the bacteria grow in the presence of these drugs, this indicates resistance.
The researchers said the new test could dramatically help those who have contracted multi-drug resistant TB (MDRTB), and had been shown to be highly effective where cases of TB were combined with HIV infection.
Researcher Dr David Moore said: "In one study in Lima, half of HIV patients with MDRTB were dead within two months of commencing TB treatment, the minimum time to get results from standard tests in Peru or indeed almost anywhere in the developing world.
"Their MDRTB had gone undetected and so they had received the wrong treatment.
"A correct diagnosis at the start of treatment would have improved many of their outcomes."
Professor Peter Davies, secretary of the group TB Alert, said: "This is a very exciting development, which offers the best hope of a quick diagnosis for the 50% of people in the developing world who are not detected by the current test."