Fast Strep Test Is Best

If four symptoms are present, an adult probably doesn't need follow-up throat culture test, says study

MONDAY, Dec. 17, 2001 (HealthDayNews) -- 'Tis the season for sore throats, and many doctors use a two-step process to diagnose the most severe kind: strep throat.

The procedures involve a fast-acting throat swab test, which can take as little as five minutes to detect the bacteria, and a 24-to-48 hour throat culture to confirm the diagnosis.

But a new study says the rapid strep throat tests are so accurate if certain symptoms are present that a follow-up test is not needed.

"We confirmed that the accuracy of the rapid test was better when patients had multiple [symptoms] of strep," says the study's author, Dr. Ralph Gonzales, an associate professor of medicine at the University of California, San Francisco.

"Strep" is short for the Streptococcus pyogenes bacteria, which causes the kind of sore throat that, if untreated, can lead to heart problems.

Gonzales studied the charts of almost 500 adults with sore throats who had been seen in the emergency room or an urgent care clinic. He looked at the results of their rapid test and the follow-up throat culture. He also looked for the presence of four symptoms: fever, no cough, swollen lymph nodes and white patches on the tonsils.

He found that the accuracy of the rapid test went up with each symptom that was present: If a patient had one symptom, the rapid test was 61 percent accurate in picking up strep. If two of the symptoms were present, the test was 76 percent accurate; three symptoms and the test was 90 percent accurate; and when the patient had all four symptoms, it was 97 percent accurate.

Results of the study appear in the December issue of the Annals of Emergency Medicine.

Diagnosing strep quickly is important because the sooner antibiotics are started, the faster the patient gets relief. If strep is not treated, it can develop into a more serious infection of the heart known as rheumatic fever.

Dr. John Harrington, an assistant professor of pediatrics at New York Medical College in Valhalla, N.Y., says that the study did a good job in showing that it isn't always necessary to follow up with a throat culture in adults.

However, he says, in children, it's often difficult to get a good swab of the back of the throat because children don't like to sit still for the test.

"If I get a positive, I know I have a case of strep. But if you get a negative, do you want to be the doctor that doesn't treat a case of strep that turns into rheumatic fever?" he asks.

What To Do

"If your child has a runny nose and a cough and no fever, they probably don't have strep," says Harrington. The American Academy of Family Physicians says that only 5 percent to 10 percent of all sore throats are caused by strep. "Strep throat is the only cause of sore throats that benefits from antibiotics," says Gonzales. "If the test is negative, antibiotics probably won't help."

For more information on strep throat, go to the American Academy of Family Physicians or to And, KidsHealth offers this explanation of strep for your kids to read.

SOURCES: Interviews with Ralph Gonzales, M.D., M.P.H., associate professor of medicine, University of California, San Francisco; John Harrington, M.D., assistant professor of pediatrics, New York Medical College, Valhalla, N.Y.; December 2001 Annals of Emergency Medicine
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