Immunoasssay chromatographic antigen test for rapid diagnosis of Group A beta hemolytic Streptococcus pharyngitis in children: A cross/ sectional study.

Background And Objective: Group A beta-hemolytic streptococcus (GABHS) is an important pharyngotonsillitis etiologic agent in children. The objective of this study was diagnosis of streptococcal pharyngitis based on rapid antigen detection test and conventional pharyngeal culture.

Materials And Methods: The rapid GABHS antigen detection test was compared to culture on blood agar, the gold standard for the diagnosis of this etiologic agent.

Results: Streptococcal antigen was detected in pharyngeal specimens of 34.5% of cases by rapid strip test. We detected group A Streptococcus in 17.2% of pharyngeal culture. There was no agreement between two methods ( PV < 0.1). The negative pharyngeal culture results are probably due to antibiotic usage in 43.2% of patients. Positive rapid test results in pharyngeal swab was age dependent ( P < 0.05). There was good correlation between observing the "petechia in pharynx of patients" and positive rapid test in pharyngeal swab (P < 0.004). Throat culture results were relatated to previous antibiotic usage ( P < 0.03).

Conclusion: The rapid test in pharyngeal swab is helpful for rapid diagnosis and treatment of GABHS pharyngitis. Diagnosis of GABHS pharyngitis based on soley clinical findings is misleading in the majority of cases. Petechia observed in pharynx of the cases was highly predictive of streptococcal pharyngitis.