Programme no. 342-OP
C-reactive protein rapid test does not predict group A β-haemolytic streptococcal infection in patients with sore throat
Carl Llor*1, Carolina Bayona2, Ana Moragas3, Olga Calviño4, Silvia Hernandez5, Josep Maria Cots6
1Primary Care Centre Jaume I,Catalan Institute of Health,Tarragona,Spain, 2Primary Care Centre Valls,Catalan Institute of Health,Valls,Spain, 3Primary Care Centre Jaume I,Catalan Institute of Health,Tarragona,Spain, 4Primary Care Centre Jaume I,Catalan Institute of Health,Tarragona,Spain, 5Primary Care Centre Jaume I,Catalan Institute of Health,Tarragona,Spain, 6Primary Care Centre La Marina,Catalan Institute of Health,Barcelona,Spain
* = Presenting author
Objectives: To know the relationship between the aetiology of sore throat and CRP levels.
Background: Several studies have found that C-reactive protein (CRP) testing significantly reduces antibiotic prescribing in patients with respiratory tract infections, since elevated CRP levels are associated with bacterial aetiology. Among patients with sore throat only those cases caused by group A β-haemolytic streptococcus (GABHS) are supposed to be treated with antibiotics. In some countries GPs rely on the determination of CRP to guide antibiotic treatment in sore throat.
Results: A total of 149 patients were enrolled. The most frequent aetiology was GABHS, present in 83 cases (55.7%). No germs were identified in 29 patients (19.5%). The highest level of CRP was observed among patients with group C β-haemolytic streptococcus infection (56.3 mg/L; 95%CI 25.7–86.9), followed by GABHS (34.4 mg/L; 95%CI 25.6–43.3). However, patients in whom no germs were identified had a mean CRP concentration of 27.9 mg/L (95%CI 11.0–44.9).
Material/Methods: An observational study was undertaken in an urban health centre between 2010 and 2012. Adults aged 18 years or more with acute pharyngitis and the presence of the four Centor criteria —history of fever, presence of tonsillar exudates or hypertrophy, presence of tender cervical glands, and absence of cough— were consecutively recruited. All the patients underwent a pharyngotonsillar swab for microbiological culture and underwent a CRP rapid test in the consultation.
Conclusion: This study has several limitations. Only patients with the four Centor criteria were recruited, outcomes were not collected and neither was the evolution of symptoms measured, but we consider these limitations as not important since our goal was to identify the association of CRP levels with the aetiology of sore throat. The microbiological study did not take the study of anaerobes into account, and some of the patients with no germs identified could have been infected with anaerobes. This study shows that CRP is not useful for distinguishing patients with GABHS infection from other aetiologies that do not require antibiotic therapy.
Points for discussion:
1. Do you consider that a CRPitis does actually exist in the Nordic countries?
2. On the basis of these results, do you consider that other causes of sore throat should also be treated with antibiotics?