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Global Health

Rapid Malaria Tests Work, but With Unexpected Drawbacks

A health care worker taking a blood sample of a mother to test for malaria in Lagos, Nigeria. A study found that rapid tests have greatly improved treatment, but that many people who tested positive still did not get the proper drugs or were overprescribed antibiotics.Credit...Pius Utomi Ekpei/Agence France-Presse — Getty Images

Rapid diagnostic tests have greatly improved malaria treatment in the last decade, but they also had some unexpected bad consequences, a large new study has found.

As hoped, the tests — which use only a drop of blood and provide results in about 15 minutes — substantially decreased how many patients with fever were incorrectly given or sold malaria drugs when they did not have malaria.

But the number of patients who got antibiotics instead shot up, even if they were not tested for bacterial infections — a practice that encourages the emergence of drug-resistant germs.

The study also found that a disturbing number of people who tested positive for malaria still did not get malaria drugs. At five of eight testing sites in Africa, more than 20 percent did not.

“This surprised us, but we don’t have a lot of insight into why it happens,” said Dr. Heidi Hopkins, a malaria diagnostics expert at the London School of Hygiene and Tropical Medicine and one of the study’s authors.

Drug shortages were uncommon at most study sites, she said. But it is also possible that nurses inured to shortages might have held back free drugs from patients who were not seriously ill or who appeared able to buy the drugs elsewhere.

The study, published in The American Journal of Tropical Medicine and Hygiene, looked at more than 500,000 patient visits to rural or urban clinics in five African countries and Afghanistan.

Over all, 75 percent of the patients got malaria drugs or an antibiotic, regardless of their test results.

In most sites, between 40 to 80 percent of those who did not have malaria got antibiotics, even though the majority probably had viral infections, which antibiotics do not help. The best treatment is usually rest, fluids and a mild fever-reducing drug.

One advanced study in Zanzibar looking into all causes of fever found that only about 22 percent were bacterial, Dr. Hopkins said. But complex testing in poor countries is impossible, so doctors and nurses often offer antibiotics to sick patients just in case the cause is bacterial.

“We definitely can’t blame them for doing that,” Dr. Hopkins said. “Some of these patients are mothers who bring their kids in from 20 kilometers away on motorcycles or in minibuses. You can certainly understand why a health care worker would be reluctant to just send them home with a pat on the head and advice to take paracetamol and drink fluids.”

The study was part of a long effort paid for by the Bill and Melinda Gates Foundation to investigate how artemisinin, a malaria drug invented in China and introduced about 15 years ago, could be widely used — but not overused.

Malaria experts hope to slow down the emergence of artemisinin-resistant strains. Deaths from malaria have dropped 60 percent since 2000, partly because the drugs are so effective — but resistant parasites are turning up, especially in Southeast Asia.

In 2010, the World Health Organization strongly endorsed rapid malaria tests, and now more than 300 million are used each year.

Although the ideal way to diagnose malaria is still to examine stained blood under a microscope, many clinics lack microscopes and trained staff.

A version of this article appears in print on  , Section D, Page 4 of the New York edition with the headline: Rapid Malaria Tests Work, With Drawbacks. Order Reprints | Today’s Paper | Subscribe

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