The Use of Bacterial DNA From Saliva for The Detection of GAS Pharyngitis

Background: Acute tonsillitis is one of the most common medical conditions for which children and young adults seek medical advice. Despite different methods of detection, all tests are based on GAS sampling using a throat swab. However, obtaining the swab can elicit vomiting and is often accompanied by fear and apprehension in children. The aim of this study was to find a non-invasive method for the detection of GAS pharyngitis.

Methods: A classic throat swab was obtained for culture, and a saliva sample was taken by voluntary spitting from 100 subjects recruited from Hadassah Medical Center and a Meuhedet Health Care Organization clinic (HMO). Real time PCR (RT-PCR) was performed to detect GAS dnaseB specific gene in the saliva samples. Throat swabs were sent for bacterial culture.

Results: 56% of the throat cultures were positive for GAS and 48% of the PCR samples were positive. The overall sensitivity and specificity of the saliva PCR method was 79% and 91% respectively; NPV and PPV were 77% and 92% respectively. When excluding patients who presented on the first day of fever, sensitivity and specificity increased to 90% and 100% respectively. No other anamnestic or clinical findings increased the yield of the test.

Conclusion: Saliva- based PCR amplification of GAS DNA method is effective in detection of GAS pharyngitis. Further studies are needed to achieve detection rates to replace the traditional throat swab- based approach.