Test may lower antibiotic use

New method could cut unnecessary prescriptions.

Antibiotics have no effect on viral coughs and colds. Credit: © Creatas

A new test could help doctors determine whether patients will benefit from antibiotics. The technique could halve prescriptions of the antibacterial drugs, and help slow the rise of antibiotic-resistant 'superbugs'.

Antibiotics are effective against many types of bacteria, but don't work against viruses. Despite this they are routinely prescribed for coughs, colds and chest infections, which are mainly caused by viruses.

The unnecessary prescriptions occur because bacterial and viral infections can have similar symptoms, such as sore throat and fever. So clinicians often prescribe antibiotics to err on the side of caution.

But the more antibiotics are used, the greater the chance that bacteria will evolve to resist them. So many researchers worry that the expensive practice of over-prescription is fuelling the development of superbugs that can't be killed. "Antibiotic overuse is a huge problem," says Anthony Suffredini from the National Institutes of Health at Bethesda, Maryland, who works in critical-care medicine.

So Beat Müller from the University Hospital in Basel, Switzerland, and colleagues investigated a test that could better determine when antibiotics are really needed. The test works by measuring levels of a protein called procalcitonin in the blood. When someone has a bacterial infection, their procalcitonin levels shoot up. Viral infections prompt a much smaller increase.

The team trialled the test on 243 patients with infections of the lower respiratory tract, such as bronchitis and pneumonia1. Half of the patients received normal care - doctors used X-rays, laboratory tests and clinical symptoms to assess whether an infection was bacterial in nature. As a result, 83% were given antibiotics.

In the other half of patients, blood samples were taken and examined for procalcitonin. The test took about an hour. About 43% had high procalcitonin levels and were prescribed antibiotics.

Despite the very different treatments, both groups did equally well in terms of recovery - nearly all the patients got better. "The test halves antibiotic use, without altering the clinical outcome," says Müller.

Mucous tests

Independent tests were later done to verify whether the patients had bacterial infections or not. Samples of their mucus were cultured in the lab for several days to see if bacteria would grow. The results of this test, which is not always accurate, indicated that only about 20% of patients in both groups had bacterial infections.

“Antibiotic overuse is a huge problem Anthony Suffredini, , NIH”

Even if the procalcitonin test still results in some over-prescription of antibiotics, it improves the situation dramatically, says Müller.

Nearly all of the world's significant bacterial infections are becoming resistant to antibiotics. In 2002, doctors reported the first case of a new superbug that is completely resistant to the antibiotic vancomycin, one of the last lines of defence against bacteria.

The new test is a good first step to tackling this problem, says Suffredini. It now needs to be tested on larger patient numbers with different types of infections.


  1. 1

    Christ-Crain, M. et al. Effect of procalcitonin-guided treatment on antibiotic use and outcome in lower respiratory tract infections: cluster-randomised, single-blinded intervention trial. The Lancet, 363, 600 - 607, (2004).

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Pilcher, H. Test may lower antibiotic use. Nature (2004). https://doi.org/10.1038/news040216-17

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