Comparison of Two Rapid Antigen Detection Tests for Diagnosis of Group A Streptococcal Pharyngotonsillitis

ABSTRACT

PURPOSE: Recently, a number of rapid antigen detection tests have been available to diagnose group A streptococcal pharyngotonsillitis. The purpose of this study was to determine the sensitivity, specificity and consistency of the two rapid antigen detection tests. METHODS: Among the patients who visited our clinic from November 2001 to February 2002, 61 patients who had clinical findings of pharyngeal erythema or edema, pharyngeal exudates and soft palatine petechiae were enrolled in our study. A total of 61 patients were tested with rapid antigen detection tests and throat culture. BD LINK2TM Strep A(Becton, Dickinson and Company, U.S.A.) and QuickVue(R) In-LineTM(Quidel Corporation, U.S.A.) were selected for rapid antigen detection tests. RESULTS: Of the 61 patients tested, 22 patients were confirmed as group A streptococcal pharyngotonsillitis by throat culture. The BD LINK2TM Strep A had a sensitivity of 81.8% and a specificity 89.7%. The positive and negative predictive values were 81.8% and 89.7%, respectively. The QuickVue(R) In-LineTM had a sensitivity of 77.3% and a specificity of 100%. The positive and negative predictive values were 100% and 88.6%, respectively. The kappa values of BD LINK2TM Strep A and QuickVue(R) In-LineTM were 0.72 and 0.81, respectively. CONCLUSION: In addition to high sensitivity, specificity and consistency, both kits are easy to use and simple to interpret, and therefore have the potential to be used with backup throat culture for diagnosis of acute pharyngotonsillitis.