Sensitivity and Specificity of Rapid Antigen Test in Diagnosis of Streptococcal Upper Respiratory Tract Infection

Abstract

Background: Sore throat is one of the most common reasons for visits to family physicians. While most patients with sore throat have an infectious cause (pharyngitis), fewer than 20% have a clear indication for antibiotic therapy (i.e. group A β-hemolytic streptococcal infection). Reducing the number of unnecessary antibiotic prescriptions given for common respiratory infections has been recommended as a way to limit bacterial resistance.

Objective: This study aimed to detect the sensitivity and specificity of a rapid antigen detection test (ICT) for diagnosis of throat infection caused by group (A) β- hemolytic streptococci, compared with culture as the gold standard test.

Materials and methods: A total of 76 patients with new upper respiratory tract infections accompanied by sore throat were assessed by a physician. Pharyngeal swabs were obtained from all patients and both rapid test and throat culture were performed.

Results: Streptococcus pyogenes was identified in 22 out of 76 throat swabs (28.9%), of these 16 were positive by both ICT and culture. 19 (25%) were positive by ICT and also 19 (25%) were positive by culture. The sensitivity of the ICT was 86.4% and specificity was 95%.

Conclusion: Our study supports new approaches to diagnosis of sore throat by using ICT of streptococcus pyogenesas rapid, simple, and easy method in laboratory for any patients with centor criteria, to avoid the misdiagnosis and unnecessary antibiotic use.