From the Guidelines
For children with a negative strep test, a throat culture should still be sent out for testing. This recommendation is based on the 2012 update by the Infectious Diseases Society of America, which states that in children and adolescents, negative rapid antigen detection tests (RADT) should be backed up by a throat culture 1. The clinical features alone do not reliably discriminate between Group A Streptococcal (GAS) and viral pharyngitis, except when overt viral features are present. Key points to consider include:
- The low incidence of GAS pharyngitis in adults and the risk of subsequent acute rheumatic fever is generally exceptionally low in adults with acute pharyngitis, but this is not the case for children 1
- Positive RADTs do not necessitate a back-up culture because they are highly specific, but negative RADTs should be backed up by a throat culture in children and adolescents 1
- Anti-streptococcal antibody titers are not recommended in the routine diagnosis of acute pharyngitis as they reflect past but not current events 1 The decision to culture after a negative rapid test is particularly important in children because they have higher rates of strep throat than adults and are at greater risk for complications like rheumatic fever if strep infections go untreated. In settings where follow-up might be difficult or in children with strong clinical suspicion (fever, tonsillar exudates, tender cervical lymphadenopathy, absence of cough), cultures are especially valuable.
From the Research
Diagnosis of Strep Pharyngitis in Children
- The diagnosis of strep pharyngitis in children typically involves the use of rapid antigen testing, followed by a throat culture if the rapid test is negative 2.
- Clinical decision rules, such as the presence of fever, tonsillar exudate, cervical lymphadenitis, and patient age, can help assess the risk of group A beta-hemolytic streptococcal infection 2.
- A negative rapid antigen test result does not rule out the possibility of strep pharyngitis, and a throat culture is recommended in children and adolescents to confirm the diagnosis 2.
Use of Throat Cultures in Children
- Throat cultures are recommended in children and adolescents after a negative rapid antigen test result to confirm the diagnosis of strep pharyngitis 2.
- However, in children who have been recently treated for strep pharyngitis, the use of rapid antigen testing may lead to false positive results, and a throat culture is recommended instead 3.
- The false positive rate of rapid antigen testing is higher in younger children who have been recently treated for strep pharyngitis, highlighting the importance of using throat cultures in this population 3.