RESUMO
IMPORTANCE: The use of the rapid antigen-detection test (RADT) has become the standard of care in the early diagnosis of group A beta-hemolytic Streptococcus (GAS) pharyngitis. Concern has been expressed over increased false positives when the child had been treated recently for GAS pharyngitis, resulting in over use of antibiotics. OBJECTIVE: To determine if the false positive rate for RADT is increased in children recently treated for GAS pharyngitis. METHODS: We conducted a prospective study to evaluate 300 children from a private practice with acute pharyngitis who were treated for GAS pharyngitis within the preceding 28 days (study group) compared to 306 children of comparable age who had not been previously treated (control group). RADT and throat culture were performed on all children presenting with signs and symptoms of acute pharyngitis. The false positive and false negative rates were determined and compared in both groups. RESULTS: The false positive rate of 11.5% (23/200) in the study group was significantly higher than the false positive rate of 0 in the control group. False positives were more likely to occur in younger children. INTERPRETATION: These data would indicate that while RADT is reliable in most children, it can lead to over treatment in children who have been recently treated for GAS. In children treated in the preceding 28 days for GAS pharyngitis, the presence of infection should be determined with a throat culture only. Treatment based on a positive RADT should be reserved for children not recently treated for GAS pharyngitis.
