Predicting streptococcal pharyngitis in adults in primary care: a systematic review of the diagnostic accuracy of symptoms and signs and validation of the Centor score.

Jolien Aalbers,Wai-Sun Chan,Kirsty K O'Brien,Tom Fahey,Gavin A Falk,Conor Teljeur,Borislav D Dimitrov

doi:10.1186/1741-7015-9-67

Abstract

BackgroundStratifying patients with a sore throat into the probability of having an underlying bacterial or viral cause may be helpful in targeting antibiotic treatment. We sought to assess the diagnostic accuracy of signs and symptoms and validate a clinical prediction rule (CPR), the Centor score, for predicting group A β-haemolytic streptococcal (GABHS) pharyngitis in adults (> 14 years of age) presenting with sore throat symptoms.MethodsA systematic literature search was performed up to July 2010. Studies that assessed the diagnostic accuracy of signs and symptoms and/or validated the Centor score were included. For the analysis of the diagnostic accuracy of signs and symptoms and the Centor score, studies were combined using a bivariate random effects model, while for the calibration analysis of the Centor score, a random effects model was used.ResultsA total of 21 studies incorporating 4,839 patients were included in the meta-analysis on diagnostic accuracy of signs and symptoms. The results were heterogeneous and suggest that individual signs and symptoms generate only small shifts in post-test probability (range positive likelihood ratio (+LR) 1.45-2.33, -LR 0.54-0.72). As a decision rule for considering antibiotic prescribing (score ≥ 3), the Centor score has reasonable specificity (0.82, 95% CI 0.72 to 0.88) and a post-test probability of 12% to 40% based on a prior prevalence of 5% to 20%. Pooled calibration shows no significant difference between the numbers of patients predicted and observed to have GABHS pharyngitis across strata of Centor score (0-1 risk ratio (RR) 0.72, 95% CI 0.49 to 1.06; 2-3 RR 0.93, 95% CI 0.73 to 1.17; 4 RR 1.14, 95% CI 0.95 to 1.37).ConclusionsIndividual signs and symptoms are not powerful enough to discriminate GABHS pharyngitis from other types of sore throat. The Centor score is a well calibrated CPR for estimating the probability of GABHS pharyngitis. The Centor score can enhance appropriate prescribing of antibiotics, but should be used with caution in low prevalence settings of GABHS pharyngitis such as primary care.

Highlights

Stratifying patients with a sore throat into the probability of having an underlying bacterial or viral cause may be helpful in targeting antibiotic treatment
Upper respiratory tract infections such as acute pharyngitis represent a substantial portion of the cases seen in primary care [1]
Diagnostic accuracy of the Centor score As the Centor score is recommended by guidelines as a decision aid for empirical antibiotic use [4,17], we explored the diagnostic accuracy of the score at different cut points

Summary

Introduction

Stratifying patients with a sore throat into the probability of having an underlying bacterial or viral cause may be helpful in targeting antibiotic treatment. Throat cultures are currently considered to be the ‘reference standard’ for the diagnosis of streptococcal pharyngitis [8,9] This test has a number of limitations in practice; it is relatively expensive; the laboratory tests take 1-2 days leading to delays in starting treatment; and excessive false positive results in asymptomatic pharyngeal carriers may lead to over treatment [10,11]. CPRs are evidence-based tools that allow clinicians to stratify patients according to their probability of having a particular disorder. They can be used to provide a rational basis for treatment

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