a SLACK Incorporated newspaper
January 1999
DENVER - Before pediatricians can determine a treatment for pharyngitis, they should first determine whether it is caused by group A streptococci (GAS), according to Ellen R. Wald, MD,professor of pediatrics and otolaryngology, Children's Hospital of Pittsburgh and University of Pittsburgh School of Medicine.
Although GAS pharyngitis is the most common bacterial cause of acute pharyngitis, only a minority of patients with pharyngitis are infected by group A streptococci. In addition, GAS pharyngitis is the only commonly occurring form of acute pharyngitis for which antibiotic therapy is definitely indicated, said Wald, a member of the Infectious Diseases in Children editorial board, here at the 36th Annual Meeting of the Infectious Diseases Society of America (IDSA).
Therefore, she said, before the pharyngitis can be treated, physicians must first determine whether the infection is being caused by GAS. She defined six indicators which help make the diagnosis: fever of 101°-102° F; cervical denopathy; a typical finding of pharyngitis (i.e. erythema, swelling or exudate); school-age children (5-15 years); seasonality (winter/spring); and, absence of upper respiratory infection symptoms (cough, coryza, conjunctivitis).
If a patient has all six indicators, the diagnosis is 80% to 85% likely to be GAS. However, if the patient has five of six features, the predictability drops to 50%.
"It turns out that only 15% of all children come in with all the classic features of streptococcal infection," she said.
A single throat culture has a sensitivity of 90% to 95% in detecting the presence of GAS in the pharynx, but the culture must be done correctly. However, anaerobic incubation and special culture media are not recommended routinely because they can result in false positives, Wald added.
A positive rapid diagnostic test for GAS needs to be followed by the performance of a standard throat culture, Wald said, noting that Michael Gerber, MD, and Stan Shulman, MD, have presented conflicting evidence on the subject.
"In 1998, when we teach about this we need to encourage people to get two swabs. If the first swab is positive for a rapid diagnostic test, we don't have to worry about it. If the swab is negative I think the requirement is that we do a back-up culture," she explained.
Follow-up cultures should not be performed routinely on asymptomatic patients recovering from GAS infection because a positive result often means the patient is a carrier. GAS is normal flora for some children; that number may vary from 5% in the summer to as high as 15% to 20% in the winter, she said.
"Nonetheless, when we see a child with acute pharyngitis we make an agreement with ourselves that if we do a throat culture that identifies GAS, we will regard it as the causative agent," Wald said. "We don't have any other practical ways to solidify that diagnosis."
According to Jack M. Gwaltney, MD,professor of medicine at the University of Virginia Medical Center, Charlottesville, Va., there are specific circumstances under which a follow-up culture is indicated: recurrent infections, to be sure the organism is eradicated; a child in a family with one or more people who have had rheumatic fever; a child with rheumatic fever or a history of rheumatic fever; and, in an outbreak of streptococcal disease.
Short-course therapy works for some pediatric infections, but not all. According to IDSA guidelines, short courses of therapy for GAS pharyngitis are not recommended. The treatment of choice for patients with acute pharyngitis caused by GAS is penicillin V or amoxicillin two or three times daily.
Wald stressed the importance of completing the course of therapy; if a child skips a dose or two, the parent must be prepared to extend the regimen to 11 or 12 days. This must be made clear to the parent, because if the child has taken amoxicillin 90 minutes before returning to the pediatrician's office, there may be enough amoxicillin in the secretions to make the culture negative, she said.
Very early therapy of pharyngitis due to GAS may impair the development of local immune responses to the infection and leave the patient susceptible to reinfection with the same M-type of GAS. However, there are conflicting data on this issue, Wald said.
"There are three studies that have examined the issue of whether the timing of antibiotic therapy for GAS throat infections in children (immediate treatment or a 48-hour delay) can alter the likelihood that the child develops recurrent GAS," she said.
If a patient presents with numerous episodes of pharyngitis due to GAS and the patient is not a carrier, Gwaltney said it is not appropriate to give the patient a trial of prophylaxis for several months, despite past recommendations.
Children who are carriers of GAS are not at risk for rheumatic fever, and carriers are not effective at transmitting the organism. The recommended treatment for the management of a GAS carrier is clindamycin (Cleocin, Pharmacia & Upjohn) at 20 mg/kg/day in three or four divided doses for 10 days.
For your information:
- Gwaltney J, Wald E. Short course antibiotics for pediatric upper respiratory tract infections. Session 76. 36th Annual Meeting of the Infectious Diseases Society of America. Nov. 12-15. Denver.
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