How is streptococcal pharyngitis diagnosed?

Updated: Dec 05, 2018
  • Author: Rajendra Bhimma, MBChB, MD, PhD, DCH (SA), FCP(Paeds)(SA), MMed(Natal); Chief Editor: Craig B Langman, MD  more...
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The diagnosis of streptococcal pharyngitis on clinical grounds alone is uncertain, and only 10-20% of the patients who present with sore throat in general clinical practice have a positive culture for group A streptococci. [66] Several clinical scoring systems have been developed to increase the accuracy of diagnosis for the prescription of antibiotics. The most commonly used is that of Centor et al [67] and McIsaac et al. [68] These have a range of 1-4 and incorporate age as a risk factor. The following is the McIsaac score, showing each criterion and its corresponding score:

  • Temperature higher than 38º C and no cough - 1 point

  • Tender anterior cervical adenopathy - 1 point

  • Tonsillar swelling or exudates - 1 point

  • Age between 3 and 14 years - 1 point

Age 15-44 years is assigned no points, and age older than or equal to 44 years garners -1 point. Based on the scoring systems, it is recommended that antibiotic treatment is administered based on clinical grounds alone when the score is 4, antibiotic treatment is not recommended (and culture is unnecessary) when the score is 0 or 1, and culture should be obtained and treatment given only when the result is positive if the score is 2 or 3. Rapid test for streptococcal antigen detection may be used as a confirmatory test for children with tonsillar exudate. [69] However, the sensitivity is too low to support use without culture confirmation of negative results. [70]

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