Does a negative throat culture result rule out a diagnosis of streptococcal pharyngitis (strep throat)?

Updated: Sep 07, 2018
  • Author: Zartash Zafar Khan, MD, FACP; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Answer

Although a negative throat culture finding essentially rules out the diagnosis of streptococcal pharyngitis, a positive culture finding unfortunately cannot be used to differentiate between acute infection and asymptomatic carriage. Some studies have reported that the degree of positivity of the culture may, by quantifying the load of organisms, assist in making this differentiation. In practice, however, assuming that all positive results in appropriately cultured patients represent streptococcal infection and accepting that some degree of overtreatment is inevitable is probably best.

The video below demonstrates a throat culture.

Throat swab. Video courtesy of Therese Canares, MD; Marleny Franco, MD; and Jonathan Valente, MD (Rhode Island Hospital, Brown University).

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