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August 5, 1992

Diagnosing Streptococcal Pharyngitis

Author Affiliations

University of Minnesota Minneapolis

JAMA. 1992;268(5):599. doi:10.1001/jama.1992.03490050047008

To the Editor.  —The article entitled "Insensitivity of Rapid Antigen Detection Methods and Single Blood Agar Plate Culture for Diagnosing Streptococcal Pharyngitis" by Wegner and colleagues,1 while attempting to assist clinicians in management of group A streptococcal infections, unfortunately reaches unjustified conclusions without taking a number of important factors into consideration.First and most important, it is very difficult to believe that experienced microbiologists can find group A streptococci on only 58% of the plates after 24 hours and on only approximately 70% of the plates after 2 days. Even if there is an accepted discordance rate (one positive and one negative) of about 10% when using two swabs as shown in reference 8 of the article, this still indicates that those who read the single plates missed about 20%. This is unacceptably high for a laboratory.The authors could have attempted to explain this unexpected finding by performing