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#246 Just wait a minute: Point-of-care testing for Group A Streptococcal pharyngitis

 In patients with sore throat, how accurate are point-of-care tests in the diagnosis of Group A beta-hemolytic streptococcal (GABHS) pharyngitis?

Point-of-care testing, including rapid antigen detection tests and newer nucleic acid detection tests for GABHS pharyngitis are useful for ruling in a diagnosis of GABHS when positive (specificity 95%-99%). Nucleic acid detection tests may be more sensitive than rapid antigen detection tests (92% versus 85%). While immediate testing and treatment may not always be required, populations at increased risk of GABHS complications, such as Canada’s Indigenous populations, are more likely to benefit. 

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Rapid antigen detection tests versus culture (3 systematic reviews, 43-98 studies including 18,464-101,121 patients):1-3 
  • Sensitivity consistently ~85%, specificity consistently ~95%.1-3 
  • Positive likelihood ratio (LR+) 16.8, Negative likelihood ratio (LR-) 0.16. 
Nucleic acid detection tests versus culture: 
  • 1 systematic review, 6 studies (1937 patients):3 
    • Sensitivity=92%, specificity=99%. 
    • LR+ 92, LR- 0.08. 
  • Evidence published after above reviews:4-6 
    • Sensitivity=89-100%, specificity=91-100%. 
  • No significant difference in point-of-care performance between adult and pediatric populations.1-3 
  • Limitations: included studies had high heterogeneity, rapid testing not currently funded publicly. 
  • LR+ above 10 indicates test is a good help at ruling-in diagnosis. 
  • Clinical decision rules (i.e. CENTOR) have limited predictive value for diagnosing GABHS pharyngitis:7 
    • Meta-analysis (11 studies):7 Sensitivity=49% specificity=82%, LR+ 2.68. 
  • Empiric treatment for sore throat is common (~60%).8 Point-of-care testing may improve appropriate antibiotic prescribing.9 
  • Antibiotics for GABHS significantly reduces:10 
    • Sore throat at day three: 44% versus 71%, number needed to treat (NNT)=4. 
    • Peritonsillar abscess 0.1% versus 2%, NNT=47. 
    • Rheumatic fever 0.6% versus 1.7%, NNT=90. 
      • (rheumatic fever data from pre-1950, incidence has declined significantly in developed countries). 
  • Populations with higher incidence of GABHS complications, such as Canada’s Indigenous population, are more likely to benefit from antibiotic treatment.11-13 
  • Many international guidelines consider GABHS pharyngitis self-limiting and do not recommend antibiotic treatment.14 
  • Delayed antibiotic prescriptions decrease antibiotic utilization with no significant impact on symptom duration, or clinical outcomes, in GABHS pharyngitis.15 

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  • Rodger Craig MPH
  • Christina Korownyk MD CCFP

1. Stewart EH, Davis B, Clemans-Taylor BL, et al. PLoS One. 2014 4;9(11):e111727.

2. Cohen JF, Bertille N, Cohen, R, et al. Cochrane Database Syst Rev. 2016; 2016(7):CD010502.

3. Lean WL, Arnup S, Danchin M, et al. Pediatrics. 2014; 134(4):771-81.

4. Berry GJ, Miller CR, Moreno Prats M, et al. J Clin Microbiol. 2018; 56(3):e01310-17.

5. Wang F, Tian Y, Chen L, et al. Clin Pediatr (Phila). 2017 Oct; 56(12):1128-1134.

6. Weinzierl EP, Jerris RC, Gonzalez MD, et al. Am J Clin Pathol. 2018 Jun 19 [epub ahead of print].

7. Aalbers J, O'Brien KK, Chan W, et al. BMC Med. 2011; 9:67.

8. Barnett ML, Linder JA. JAMA Intern Med. 2014; 174(1):138-40.

9. Rao A, Berg B, Quezada T, et al. BMC Pediatr. 2019; 19(1):24.

10. Spinks A, Glasziou PP, Del Mar CB. Cochrane Database Syst Rev. 2013 Nov 5;(11):CD000023.

11. Bocking N, Matsumoto CL, Loewen K, et al. Open Forum Infect Dis. 2016; 4(1):ofw243.

12. Madden S, Kelly L. Can Fam Physician. 2009; 55(5):475-8.

13. Ralph AP, Holt DC, Islam S, et al. Open Forum Infect Dis. 2019; 6(4):ofz097.

14. Van Brusselen D, Vlieghe E, Schelstraete P, et al. Eur J Pediatr. 2014 Oct;173(10):1275-83.

15. Spurling GK, Del Mar CB, Dooley L, et al. Cochrane Database Syst Rev. 2017 Sep; 2017(9):CD004417.

Authors do not have any conflicts of interest to declare.

Les auteurs n’ont aucun conflit d’intérêts à déclarer.