An office-based guide to diagnosing streptococcal pharyngitis

May 1, 2006

Is that sore throat "strep"? Which patients should you test-and how? Does every rapid test require a backup throat culture? Here's what you need to know.

DR. ARMENGOL is a pediatrician in private practice at Pediatric Associates of Charlottesville, Va., and an assistant clinical professor of pediatrics at the University of Virginia School of Medicine, Charlottesville.

DR. HENDLEY is professor of pediatrics, University of Virginia School of Medicine.

DR. SCHLAGER is professor of pediatrics and emergency medicine, University of Virginia School of Medicine.

Traditionally, GAS has been diagnosed by throat culture,1 with results available within 24 to 48 hours. Newer technologies-specifically, rapid antigen detection tests (RADTs)-provide results at the time of the office visit. Although the specificity of RADTs is very high, their lower sensitivity compared with throat culture makes them unreliable for ruling out disease.

Recent guidelines from the American Academy of Pediatrics (AAP) Committee on Infectious Diseases2 and the Infectious Disease Society of America (IDSA)3 state that a negative RADT in a child requires a backup throat culture for confirmation. Both sets of guidelines, however, suggest that the physician can forgo backup culture if the sensitivity of the RADT has been determined to be comparable to throat culture in the physician's practice setting. The guidelines do not discuss how office laboratories should compare RADT with throat culture.

Research has shown that 15% to 25% of pediatricians4,5 and family practitioners5 do not follow recommended guidelines for diagnosing and treating GAS pharyngitis. Moreover, a recent study6 indicated that only half of children with a sore throat who are treated with an antibiotic actually undergo testing for GAS infection. With these facts in mind, we review the highlights of GAS pharyngitis in children and discuss strategies for making the correct diagnosis in an office setting.

Microbiology

How GAS spreads