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Word of the Day

Confirmation of negative strep result may be unnecessary in adults

Clinical Question:
Is it necessary to confirm a negative rapid antigen test result for group A streptococcus in adults?

Bottom Line:
In this study of more than 15,000 patients with acute pharyngitis, of whom only 1 in 5 will have group A beta-hemolytic streptococcal (GABHS) infection, the false negative rate of rapid antigen testing was only 6%, which begs the question of why it is done. Test results didn't have a major effect on the prescription of antibiotics, with 45% of patients with a confirmed negative test result treated anyway. (LOE = 2b)

Reference:
Nakhoul G, Hickner J. Management of adults with acute streptococcal pharyngitis: minimal value for backup stress testing and overuse of antibiotics. J Gen Intern Med 2013;28(6):830-834.  [PMID:23054930]

Study Design:
Cohort (prospective)

Funding:
Government

Setting:
Outpatient (primary care)

Synopsis:
In the United States, adults with sore throat are tested for GABHS with a rapid antigen detection test and, if the result is positive, treated with antibiotics. Because of concern over the false negative rate of the antigen test, many institutions have a policy of confirming negative test results. The researchers conducting this study evaluated the results of all 20,474 adults diagnosed with acute pharyngitis and tested for GABHS in a single healthcare system. The overall likelihood of GABHS was 19.5%. Most (92%) of the patients who had an initial negative antigen test result had confirmatory testing. Of these 15,555 patients, only 6% were positive. Interestingly, testing didn't seem to have a big influence on antibiotic prescribing. Almost half (45%) of patients with confirmed negative test results were treated, as were 61% of patients for whom the initial negative test result was not confirmed. The benefit of clinical identification of GABHS is also called into question by this test, since 63% of adults were prescribed antibiotics on the basis of symptoms, even though the likelihood of GABHS was less than 20%.

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