Better diagnosis and treatment of throat infections caused by group A β-haemolytic streptococci

Abstract

This study aims to assess the diagnostic value of a rapid streptococcal antigen test in addition to four clinical features in patients with sore throat, using throat culture and antibody titre as reference tests, and to evaluate the efficacy of the current antibiotics used in the treatment of throat infections caused by group A β-haemolytic streptococcus (GABHS). Four clinical features (fever [history of] ≥38˚C, lack of cough, tonsillar exudate, and anterior cervical lymphadenopathy) are recorded in 355 patients aged four years to ≥15 years. A rapid antigen diagnostic test (RADT) is performed, as well as a throat culture. Antistreptolysin O (ASO) titre is performed in patients ≥11 years. GABHS from patients are tested for susceptibility to different antibiotics. Throat cultures were positive for GABHS in 19% patients. Rapid tests were positive in 24%. Compared with throat culture, the rapid test gave a sensitivity of 91%, specificity of 91%, positive predictive value of 73% and a negative predictive value of 98%. For patients with three or four clinical features, however, the sensitivity was considerably higher at 97%. Using the ASO test as a reference, no association was found between RADT and culture results. Zithromax showed the highest prescription rate (25.5%) and produced a high cure rate (91%) in patients with GABHS pharyngitis.