Question 1: At what age do children reliably start getting group A strep pharyngitis?

A prospective observational study by Woods et al evaluated the frequency of of group A strep (GAS) in children under 3 years of age in emergency departments who have pharyngeal erythema and other upper respiratory infection (URI) symptoms.¹ There were 78 otherwise healthy children with pharyngitis ages 3 months to 3 years who met inclusion criteria, and their test results were compared to 152 asymptomatic controls of the same age. The gold standard was the throat culture. GAS was detected in 12 of 78 (15.3 percent) symptomatic patients and 5 of 152 (3.3 percent) asymptomatic patients. While 43 (66 percent) of 78 children in the symptomatic group were younger than 2 years of age, only 2 children (4.7 percent) were positive for GAS. The frequency of positive GAS cultures in age-matched controls under 2 years of age was 3 of 123 (2.4 percent). There was no significant difference (p=0.6) between the symptomatic and asymptomatic groups, suggesting that the frequency of positive results was no greater than the underlying asymptomatic GAS carrier frequency. Between 2 and 3 years of age, the frequency of positive GAS cultures between symptomatic and asymptomatic children was 29 percent versus 7 percent (p=0.03), suggesting that children older than 2 years are more likely to have GAS genuinely contributing to their symptoms.

Similarly, a separate study by Amir et al prospectively evaluated 152 children ages 3 months to 5 years who presented to a pediatrics clinic with pharyngitis and fever without recent antibiotics.² Confirmation of GAS included both a positive throat culture and elevated antistreptolysin O (ASO) titer. There were no cases of true GAS infection in children younger than 2 years of age.

A separate prospective observational study by Nussinovitch et al (1999) evaluated for GAS in 415 children ages 3 months to 5 years presenting to a pediatrics clinic with fever of 100.4º F or above and URI symptoms.³ Similar to the study by Amir et al, confirmation of GAS included both a positive throat culture and a positive ASO titer. The ASO titers were performed within 96 hours of throat swab. The numbers by age group of these 415 were 65 children ages 3–12 months, 70 children ages 13–24 months, 110 children ages 25–36 months, 90 children ages 37–48 months, and 80 children ages 49–60 months. With increasing age, both the number of true GAS infections and carrier rates increased. In both the 3–12-month age group and 13–24-month age group, the true infection frequency was not significantly different than the background carrier frequency. While this study reported children under the age of 24 months (2 years) with true GAS infections, the number of cases was very low and very similar to carrier rates, suggesting GAS may not have caused these pharyngitis/URI symptoms.

In addition to a very low frequency of true GAS infection in children under the age of 2 to 3 years, the literature also reports very low rates of acute rheumatic fever and acute post­streptococcal glomerulonephritis secondary to GAS in children under 2 years of age.⁴ In theory, antibiotics can decrease the rate of ARF, depending on local epidemiology. PSGN rates are not altered by antibiotic use.

Conclusion

Group A strep pharyngitis is very uncommon in children under 2 years of age, and possibly 3 years of age. Testing in these age groups is therefore probably not indicated in most circumstances. The incidence of true infection is similar to the carrier rate in this age group which implies that GAS is not a routine cause of pharyngitis/URI in this age group.

References

1. Woods WA, Carter CT, Schlager TA. Detection of group A streptococci in children under 3 years of age with pharyngitis. Pediatr Emerg Care. 1999;15(5):338-340.
2. Amir J, Shechter Y, Eilam N, et al. Group A beta-hemolytic streptococcal pharyngitis in children younger than 5 years. Isr J Med Sci. 1994;30(8):619-622.
3. Nussinovitch M, Finkelstein Y, Amir J, et al. Group A beta-hemolytic streptococcal pharyngitis in preschool children aged 3 months to 5 years. Clin Pediatr (Phila). 1999;8(6):357-360.
4. Bingler MA, Ellis D, Moritz ML. Acute post-streptococcal glomerulonephritis in a 14-month-old boy: why is this uncommon? Pediatric Nephrol. 2007;22(3):448-450.