Researchers found that among people with strep throat symptoms, an initial in-office test failed to detect the bacterial infection six percent of the time - but those oversights didn't lead to complications from the infection.

The findings support recent recommendations from the Infectious Diseases Society of America (IDSA) that for adult patients, doctors can rely on the rapid test results alone to make treatment decisions.

"Though I'm confident in our review of the data to say we aren't allowing serious diseases to go untreated, it's reassuring that there were no severe (complications) in persons who had a negative rapid test, but had a positive (secondary) test" in this study, said Dr. Chris Van Beneden, an epidemiologist at the U.S. Centers for Disease Control and Prevention who helped develop the IDSA guidelines.

Many doctors still send out throat swabs for backup testing after an initially negative result. Double-checking office results using a more involved DNA test is also a standard recommendation of the Joint Commission, a healthcare accreditation organization.

The Joint Commission does, however, allow doctors to opt out of backup testing if they can analyze their own procedures and show that the first, rapid test is sufficiently accurate.

The purpose of double-checking negative tests is to make sure no cases go overlooked, because untreated strep throat can develop into serious problems, such as rheumatic fever.

But extra testing costs money, so researchers wanted to see how much was spent on the testing and how many health complications were avoided because of it.

Dr. Georges Nakhoul and Dr. John Hickner at the Cleveland Clinic in Ohio collected medical records over a two-year period from 25,000 adult patients who had come to the clinic for a sore throat.

About 20,000 of the patients received an in-office strep test, and nearly 17,000 of those were negative.

The doctors sent a throat swab off for backup DNA testing for 15,500 patients, and 953 - or six percent - of those secondary tests came back positive.

No patients who were diagnosed based on the backup test developed complications related to their strep throat infection.

TOO MANY ANTIBIOTICS

Almost half of the 953 patients with a late diagnosis were prescribed antibiotics before the positive test result came back.

The other half received their prescription a couple of days after their initial doctor's visit - perhaps too late to be helpful anyway, Nakhoul said.

"By the time they got the call back from the physician to get the antibiotics, it's been two days. This is usually the window when the antibiotic is most effective... so we're not doing the patient any good," he told Reuters Health.

The results show backup testing didn't prevent any inappropriate use of antibiotics, the researchers reported in the Journal of General Internal Medicine.

Not only did many of the late-diagnosis patients get a prescription before the results of the second test came in, 45 percent of patients who had both a negative rapid test and a negative backup test also received antibiotics. Without a bacteria-related ailment, those drugs wouldn't be expected to do patients any good.

Over-prescription of antibiotics is a major public health concern, since any use of the drugs can contribute to resistance - making future infections much harder to treat.

"We know antibiotics are used inappropriately regardless of whether backup (testing) is used or not," Van Beneden told Reuters Health.

Each backup test costs patients or their insurance companies $113 at the Cleveland Clinic - which works out to a price tag of $1.7 million in this study alone.

Nakhoul said because none of the missed cases resulted in complications, the added expense isn't worth it.

For practices using an in-office rapid test, he said, "physicians should just believe the (test) and not do the second step."

SOURCE: bit.ly/Thuj4o Journal of General Internal Medicine, online October 6, 2012.

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