Accuracy of rapid strep tests in diagnosing Streptococcal pharyntgitis?

Dear Ask The Doctor: How accurate are rapid strep tests?

Dear Sean: The Rapid Strep test is a test which is used to detect the presence of Streptococcal antigen which gives us an indication of the presence of streptococcus causing acute streptococcal pharyngitis.This test is typically done with a throat swab in a doctors office and the results are available within minutes. The specificity ( ie the ability of the test to rule out the infection) is 95-98% however the sensitivity ie th ability to rule in the infection is only  75-85% ie it is more likely to have a positive test compared to a negative one even if no infection is present. If the test is negative it is usually followed by the throat swab culture which has shown to give more accurate results. All the best.