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Prescribing Antibiotics Without Sore Throat Diagnosis Is Not Cost-Effective

BOSTON – July 15, 2003 - The traditional throat culture remains the most cost-effective method to diagnose a strep throat infection, researchers at Beth Israel Deaconess Medical Center (BIDMC) and the Medical College of Wisconsin have found in a study published in the July 15 edition of the Annals of Internal Medicine.

The study reinforces the necessity of testing – whether by culture or with a rapid antigen test – to determine whether the sore throat is caused by a virus or by bacteria before a physician prescribes antibiotics. Although pharyngitis is the sixth leading cause of visits to physicians, only 10 percent of all sore throats are caused by the streptococcus bacteria that can be treated with an antibiotic such as penicillin.

Nevertheless, physicians prescribe antibiotics to 70 to 75 percent of the adults who seek treatment for a sore throat. In addition they often choose newer, expensive broad spectrum antibiotics rather that penicillin.

"I have a lot of concerns about the overuse of antibiotics by physicians, especially in cases of sore throat," says Mark D. Aronson, M.D., a primary care physician at BIDMC and a professor of medicine at Harvard Medical School. "The routine use of these drugs by physicians, particularly the use of the broad spectrum antibiotics, can lead to drug resistance, which can be hazardous to patients if they get a very serious infection."

The study analyzed five strategies in managing patients with a sore throats, including the traditional culture in which a patient's throat is swabbed and the sample is sent to the laboratory to be grown on an agar (gel) plate. In addition to this "gold standard," the other strategies evaluated were observation alone; treating all patients empirically with antibiotics; performing a rapid antigen test without a confirmatory throat culture using an optical immunoassay (OIA), and the OIA followed by a culture to confirm a negative result – with antibiotic treatment for positive results on either the throat culture or OIA.

Researchers found that all of the strategies except empirical treatment were cost-effective. Surprisingly the traditional throat culture was both the most effective and least expensive method, despite the fact it "is not a perfect test and does not provide point-of-care results."

The analysis stands in contrast to the American College of Physicians' guidelines that suggest rapid antigen tests should replace throat cultures because treatment decisions can be made in real time and patients can begin antibiotic treatment, if necessary, immediately rather than within 24-48 hours.

Nevertheless, the authors do not support the guideline recommendations for eliminating the use of the culture, noting there are cases where the antigen test is less effective in diagnosing the presence of the bacteria.

Aronson says that regardless of which test physicians use to determine the presence of strep, it is important that a test is conducted before prescribing antibiotics. Prescribing antibiotics empirically to patients with pharyngitis – with no testing whatsoever – is the worst strategy. The only time this may be cost-effective is when the chance of a strep throat is 75 percent or higher, for example when the infection breaks out within a family.

"Before treatment, it's important to determine if the sore throat is caused by a virus or by a bacteria.," says Aronson. "The physician should order a throat culture or a rapid strep test to make the diagnosis if treatment with an antibiotic is being considered. If it is not a strep throat, the antibiotics should not be prescribed."

Source: Annals of Internal Medicine

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