Selective testing strategies for diagnosing group A streptococcal infection in children with pharyngitis: a systematic review and prospective multicentre external validation study

Abstract

Background: Several clinical prediction rules for diagnosing group A streptococcal infection in children with pharyngitis are available. We aimed to compare the diagnostic accuracy of rules-based selective testing strategies in a prospective cohort of children with pharyngitis.

Methods: We identified clinical prediction rules through a systematic search of MEDLINE and Embase (1975-2014), which we then validated in a prospective cohort involving French children who presented with pharyngitis during a 1-year period (2010-2011). We diagnosed infection with group A streptococcus using two throat swabs: one obtained for a rapid antigen detection test (StreptAtest, Dectrapharm) and one obtained for culture (reference standard). We validated rules-based selective testing strategies as follows: low risk of group A streptococcal infection, no further testing or antibiotic therapy needed; intermediate risk of infection, rapid antigen detection for all patients and antibiotic therapy for those with a positive test result; and high risk of infection, empiric antibiotic treatment.

Results: We identified 8 clinical prediction rules, 6 of which could be prospectively validated. Sensitivity and specificity of rules-based selective testing strategies ranged from 66% (95% confidence interval [CI] 61-72) to 94% (95% CI 92-97) and from 40% (95% CI 35-45) to 88% (95% CI 85-91), respectively. Use of rapid antigen detection testing following the clinical prediction rule ranged from 24% (95% CI 21-27) to 86% (95% CI 84-89). None of the rules-based selective testing strategies achieved our diagnostic accuracy target (sensitivity and specificity>85%).

Interpretation: Rules-based selective testing strategies did not show sufficient diagnostic accuracy in this study population. The relevance of clinical prediction rules for determining which children with pharyngitis should undergo a rapid antigen detection test remains questionable.

Figure 1:

Selection of clinical prediction rules included in the study.

Figure 2:

External validation of the diagnostic accuracy of rules-based selective testing strategies. Graph shows sensitivity and specificity estimates with their one-sided rectangular 95% confidence regions. Numbers indicate the rules-based selective testing strategies as follows: 1 = Breese, 2 = Wald, 3 = Attia, 4 = Edmond, 5 = McIsaac and 6 = Joachim. The target zone of accuracy (sensitivity > 85%, specificity > 85%) is delineated by the dashed horizontal and vertical lines.